here the book of abstracts

Transcription

COST Chemistry D36 3rd Workshop
and
5th Management Committee Meeting
Structure-performance relationships
at the surface of functional materials
Benahavís (Málaga, Spain), 21st to 23rd of October, 2009
The main objective of the COST D36 Action is to increase the fundamental
knowledge and understanding of the chemistry occurring at surfaces and
interfaces and the factors that tune it. An interdisciplinary, combined effort is the
approach. A fundamental approach is advocated, even for industrially oriented
research projects. This requires precisely defined problems at all levels and an
interdisciplinary approach i.e. synthesis and activation of the materials;
measurement of the surface properties; understanding surface properties at the
atomic, molecular or cluster level and theoretical understanding of these
properties in relation to chemical composition and the structure of the surface.
As a consequence, the secondary objective is to gain advanced knowledge for
modelling/predicting of the structure/composition reactivity/surface properties
relationships of the materials, by means of characterisation of the bulk and
surface properties under real operation conditions and for preparing materials
with tuneable properties.
COST Chemistry D36 3rd Workshop and 5th Management Committee Meeting
4
Sponsors and collaborating institutions:
COST (European cooperation in science and technology)
http://www.cost.esf.org/
Universidad de Málaga
http://www.uma.es/
Ayuntamiento de Benahavís
http://www.benahavis.es/inicio.asp
Junta de Andalucía
http://www.juntadeandalucia.es/index.html
Ayuntamiento de Ronda
http://www.turismoderonda.es/
PID Eng&Tech
http://www.pidengtech.com/
5
Organizers
Dr. M. Olga Guerrero Pérez
Prof. Dr. José Rodríguez Mirasol
Local Committee
Dr. Jorge Bedia
Dr. Juana M. Rosas
Mr. Ricardo López Medina
Instituto de Catálisis y Petroleoquímica
Ms. Elizabeth Rojas García
Mr. Ramiro Ruiz Rosas
Ms. M. José Valero Romero
6
BOOK OF ABSTRACTS
Section I:
Scientific
Program
st
Wednesday 21
17:00 – 17:15 Welcome
Miguel A. Bañares, Action Chair
M. Olga Guerrero-Pérez, Local Organizer
17:15 – 18:00 Keynote 1
Chair: Miguel A. Bañares, Instituto de Catálisis y Petroleoquímica (CSIC) (Spain)
K1 José Manuel López-Nieto, Instituto de Tecnología Química (CSIC) (Spain)
“Synthesis, Characterization and Catalytic behaviour in partial alkane oxidation of
Multicomponent mixed oxidic”
18:00 – 20:00 Oral Session 1
Chair: Sanna Airaksinen, Helsinki University of Technology (Finland)
O1 Maria Ziolek, Adam Mickiewicz University (Poland)
“The effect of porosity of niobosilicate supports and VSbOx loading on the
ammoxidation of propane”
O2 James Sullivan, University College Dublin (Ireland)
“Towards 4-way catalysis”
O3 Gerhard Mestl, SÜD-CHEMIE AG (Germany)
“Towards an optimization of MoVNbTe-catalysts for C3-oxidation”
O4 Maricarmen Capel, Instituto de Catálisis y Petroleoquímica (CSIC) (Spain)
“Silylation of titanium-containing amorphous silica catalyst: Effect on the alkenes
epoxidation with H2O2”
O5 Lyuba Ilieva-Gencheva, Institute of Catalysis (BAS) (Bulgary)
“Preferential oxidation of CO in H2 rich stream over gold catalysts supported on doped
ceria: effect of preparation method and dopants nature”
O6 Stanislaw Dzwigaj, Université Pierre et Marie Curie (France)
“The Design of Metal-Single site Catalysts for their Application in Catalytic and
Photocatalytic Processes“
20:30 Welcome Reception
9
nd
Thursday 22
9:00 – 9:45 Keynote 2
Chair: Robert Schoonheydt, Catholic University of Leuven (Belgium)
K2 Venceslav Kaucic, National Institute of Chemistry (Slovenia)
“Microporous and Mesoporous Materials”
9:45 – 11:05 Oral Session 2
Chair: Sven Jaras, Chemical Technology, KTH (Sweden)
O7 Monica Calatayud, Université Pierre et Marie Curie (France)
“Glycerol etherification over alkaline earth metal oxides”
O8 Izabela Sobczak, Adam Mickiewicz University (Poland)
“Glycerol oxidation on gold catalysts supported on group five metal oxides –a
comparative study with other metal oxide and carbon based catalysts”
O9 Andrei Parvulescu, Utrecht University (Netherlands)
“Etherification of Glycerol and Other Biomass-Derived Polyols: New Routes to
Valuable Bulk Chemicals”
O10 Rafael Mariscal, Instituto de Catálisis y Petroleoquímica (Spain)
“Relevance of the physicochemical properties of CaO catalyst for the methanolysis of
triglycerides to obtain biodiesel”
11:05 – 11:35 Cofee Break
11:35 – 13:15 Oral Session 3
Chair: Tomás Cordero, Universidad de Málaga (Spain)
O11 J. Ángel Menéndez, Instituto Nacional del Carbón (Spain)
“Influence of porosity and surface groups on catalytic activity of carbon materials for
the microwave-assisted CO2 reforming of CH4”
O12 Frederik Tielens, Université Pierre et Marie Curie (France)
“Niobium Oxide Species in and on Silica Materials; a Molecular Picture”
O13 Enrique Rodriguez-Castellón, Universidad de Málaga (Spain)
“Study of Nanoporous Catalysts in the Selective Catalytic Reduction of NOx”
O14 Anna M. Venezia, ISMN CNR (Italy)
“New HDS catalysts supported on thiol functionalized mesoporous silica”
O15 Ángel Landa-Cánovas, Instituto de Ciencia de Materiales de Madrid (Spain)
“Structural Flexibility in ~SbVO4”
13:15 – 14:15 Lunch
14:45 Visit to Ronda
10
rd
Friday 23
9:00 – 9:45 Keynote 3
Chair: José Rodríguez-Mirasol, Universidad de Málaga (Spain)
K3 Jean Michel Léger, Université de Poitiers (France)
“Carbon powder as conducting supports for electrocatalysts in low temperature fuel
cells”
9:45 – 11:05 Oral Session 4
Chair: Guido Mul, Delft University of Technology (Netherlands)
O16 Álvaro Colina, Universidad de Burgos (Spain)
“Synthesis of Pt nanoparticles on poly(3,4-ethylenedioxythiophene) modified
electrodes for the electrocatalysis of Methanol”
O17 David Fermin, University of Bristol (UK)
“Electrochemical Hydrogen Loading in Ultrathin Assemblies of Au-Pd Nanostructures”
O18 Atilla Cihaner, Atillim University (Turkey)
“One More Step Closer to Realizing the Dream of the Polymeric RGB
Electrochromics”
O19 László Guczi, Chemical Research Center (Hungary)
“Modelling of Au/FeOx interface by in situ Sum Frequency Generation Technique”
11:05 – 11:35 Cofee Break
11:35 – 13:15 Oral Session 5
Chair: Jean Michel Léger, Université de Poitiers (France)
O20 Nikolaos Tsiouvaras, Instituto de Catálisis y Petroleoquímica (Spain)
“The effect of the Mo precursor on the nanostructure and activity of PtRuMo
electrocatalysts for Proton Exchange Membrane Fuel Cells”
O21 Luisa Maria Abrantes, Universidade de Lisboa (Portugal)
“Electrocatalytic activity of polypyrrole films incorporating palladium particles“
O22 Hubert Girault, Ecole Polytechnique Federale de Lausanne (Switzerland)
“Bio-inspired electrochemistry: From oxygen reduction to hydrogen evolution at soft
interfaces.”
O23 Stanislas Zalis, Heyrovski Institute Prague (Czech Republic)
“Density functional and electrochemical studies of the catalytic ethylene oxidation on
nanostructured Au and Pt electrodes.”
O24 Sergio García, Instituto de Catálisis y Petroleoquímica (Spain)
“An FTIR study of ternary PtSn-Rh/C for ethanol electrooxidation: effect of surface
composition “
13:15 – 14:30 Lunch
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14:45 – 15:30 Keynote 4
Chair: Viorica Parvulescu, Institute of Physical Chemistry I.G. Murgulescue (Romania)
K4 Jaques Fraissard, Laboratoire de Physique Quantique – ESPCI (France)
129
“NMR of physisorbed Xe used as a probe to investigate porous solids”
15:30 – 17:10 Oral Session 6
Chair: Maria Ziolek, Adam Mickiewicz University (Poland)
O25 Volker Ribitsch, Universitat Graz (Austria)
“Adsorption of proteins on DLC surfaces“
O26 M. Rosa Infante, Instituto de Química avanzada de Cataluña (Spain)
“Amino Acid-Based Biocompatible Surfactants”
O27 Bjšörn Lindman, University of Lund (Sweden)
“Interactions of DNA with cationic surfactants and proteins: Gels, gel nano-particles,
microstructure and phase separation”
O28 Eduardo Marques, University of Porto (Portugal)
“Symmetry-asymmetry effects on the self-assembly of ion-paired surfactant systems”
O29 Julian Ross, University of Limerick (Ireland)
“Formic Acid as a Hydrogen Source for Vapor Phase Catalytic Reactions”
17:10 – 20:00 Poster Session
18:00 – 20:00 5th Management Committee Meeting
20:30 Workshop Banquet
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Poster Contributions
1. Blanco, Gema Instituto de Catálisis y Petroleoquímica (Spain)
“Silylation of functionalized commercial silica for the direct synthesis of hydrogen peroxide
solution”
2. Zgrablich, Jorge Instituto de Física Aplicada (INFAP) (Argentina)
“Attempts to Understand the Enantioselectivity of Chiral Propylene Oxide Adsorption on NEAModified Pt Surfaces”
3. Pinazo, Aurora Instituto de Química avanzada de Cataluña (CSIC) (Spain)
“Argine-based surfactants: mixtures with 1,2 dipalmitoyl-sn-glycerol-3-phosphate monosodium
salt”
4. Pinazo, Aurora Instituto de Química avanzada de Cataluña (CSIC) (Spain)
“Lysine-based cationic surfactants: synthesis and study of the effect of the polar group on their
biological properties”
5. Pons, Ramon Instituto de Química avanzada de Cataluña (CSIC) (Spain)
“Mono acyl lysine based surfactants: self-aggregation”
6. Ivanov, Ivan Institute of Catalysis (BAS) (Bulgary)
“Gold supported on ceria doped by Me3+ (Me=Al and Sm) for water gas shift: influence of
dopant and preparation method”
7. Andreeva, Donka. Institute of Catalysis (BAS) (Bulgary)
“Redox activity of gold-molybdena catalysts: influence of the preparation method”
8. Iliopoulou, Eleni F. CPERI/CERTH (Greece)
“FTIR accessibility studies of 2,6 DTBPy adsorption on FCC catalysts”
9. La Mesa, Camilo Sapienza University (Italy)
“Supramolecular Assemblies in Association Colloids: from dilute to concentrated regimes”
10. Trejda, Maciej Adam Mickiewicz University (Poland)
“New V, Nb, Ta – FAU zeolites – texture and surface properties”
11. Ruíz-Rosas, Ramiro Universidad de Málaga (Spain)
“Lignin-based electrospun carbon microforms”
12. Bedia, Jorge Universidad de Málaga (Spain)
“2-propanol decomposition on carbon based acid and basic catalysts”
13. Valero-Romero, M. José Universidad de Málaga (Spain)
“Catalytic and non-catalytic hydrothermal carbonization of hemp biomass: the carbonaceous
product“
14. Rosas, Juana M. Universidad de Málaga (Spain)
“Surface chemistry modification of carbon supported chromium catalysts alter no reduction by
XPS analyses“
15. Pantaleo, Giuseppe ISMN-CNR (Italy)
“CH4 combustion activity of Pd catalysts supported on TiO2 incorporated mesoporous SiO2
(SBA-15 and HMS)”
16. Edolfa, Kristine Latvian Institute of Organic Synthesis (Latvia)
“Ketonization of aliphatic acids over zinc chromite catalyst”
17. Liotta, Leonarda ISMN-CNR (Italy)
13
“Supported gold catalysts for Preferential oxidation (PROX) of CO in the presence of excess H2”
18. Pospisil, Lubomir J. Heyrovsky Institute of Physical Chemistry (Czech Republic)
“Structure-Reactivity Relationships in ElectronTransfers of Helical Polyaromatic Dications”
19. Mores, Davide Utrecht University (Netherlands)
“Coke formation during the Methanol-to-Olefin Conversion: Space- and Time-resolved In-Situ
Spectroscopy on H-SAPO-34 and H-ZSM-5”
20. Tirkes, Seha Atilim University (Turkey)
“A Neutral State Green Polymeric Electrochromic Based on Acenaphtho[1,2-b]quinoxaline and
EDOT”
21. Boghosian, Soghomon University of Patras (Greece)
“Molecular structure and reactivity of MoO3/TiO2 catalysts for ethane oxidative dehydrogenation
studied by operando Raman spectroscopy“
22. López-Medina, Ricardo Instituto de Catálisis y Petroleoquímica (Spain)
“Nanostructured MoVNbTeO Oxide Catalysts for Selective Oxidation Reactions”
23. Mikolajska, Ewelina Joanna Instituto de Catálisis y Petroleoquímica (Spain)
“Operando Studies of VPO catalysts in n-butane selective oxidation reaction. Activity, selectivity
and structure transformations”
24. Tielens, Frederik Université Pierre et Marie Curie (France)
“Theoretical Study of Thiol Self Assembled Monolayer Formation on Au(111) surfaces”
25. Rojas, Elizabeth Instituto de Catálisis y Petroleoquímica (Spain)
“Theoretical Investigation of the Ammonia Adsorption Process on (110)-VSbO4 Surface”
26. Wolfgang, Grünert Ruhr-Universität Bochum (Germany)
“Peculiar response of V2O5-WO3/TiO2 DeNOx catalysts to thermal stress an investigation with
catalytic and spectroscopic tools“
27. Zhang, Yongmin Université Pierre et Marie Curie (France)
“Synthesis of novel 2:1 permethylated b-cyclodextrin-fullerene conjugates “
28. Nervi, Carlo Dipartimento di Chimica IFM (Italy)
“Electrochemical Functionalization of Glassy Carbon Electrode Surfaces by Organometallic
Moieties”
29. Hromadová, Magdaléna J. Heyrovský Institute of Physical Chemistry of ASCR (Czech
Republic)
“Self–assembled monolayers of atrazine–based thiolates and their interaction with anti–atrazine
antibody”
30. Morán, Carmen University of Coimbra (Portugal)
“DNA gel particles from single and double-tail surfactants”
31. Dias, Rita University of Coimbra (Portugal)
“Adsorption of macromolecules to responsive surfaces”
32. Mendez, Manuel Ecole Polytechnique Fédérale de Lausanne (Switzerland)
“Proton Coupled Oxygen Reduction at Liquid-Liquid Interfaces Catalyzed by Cobalt Porphine”
33. Boutonnet, Magali KTH Chemical Science and Engineering (Sweden)
“Synthesis of crystalline CeO2 nanoparticles by a novel oil-in-water microemulsion reaction
method and its use as catalyst support”
14
34. Beck, Andrea Chemical Research Center (Hungary)
“The effect of preparation method on the formation of highly active Au-promoter oxide perimeter
in promoted Au/SiO2 catalysts”
35. Benko, Timea Chemical Research Center (Hungary)
“TiO2 and CeO2 promoted Au/SBA-15 in propene total oxidation”
36. Hernandez-Alonso, M. Dolores CIEMAT-PSA (Spain)
“Selective photo-oxidation of cyclohezane on TiO2: the role of surface characteristics“
37. Alekseev, Sergyi Kiev University (Ucrania)
“Porous silicon with gold nanoparticles as laser desorption/ionization mass spectrometry
platform”
38. Gerda, Vasilyi Kiev University (Ucrania)
“Matrix synthesis and functionalisation of the ordered mesoporous carbon by palladium
nanoparticles as potential sorbent for hydrogen storage”
39. Syzgantseva, Olga Université Pierre et Marie Curie (France)
“Theoretical studies of hydrogen adsorption mechanism on ZrO2”
15
BOOK OF ABSTRACTS
Section II:
Keynote
Communications
K1
Synthesis, Characterization and Catalytic behaviour in partial alkane oxidation of
Multicomponent mixed oxidic bronzes
José M. López Nieto
Instituto de Tecnología Química, UPV-CSIC, Avda. De los Naranjos s/n, 46022-Valencia
(Spain)
[email protected]
Abstract
The selective oxidative functionalization of short chain paraffins is a formidable challenge for the
sustainable use of alkanes as feedstock. The incorporation of several functions in an adequate
structure seems to be the way to the development of active and selective catalysts for partial
alkane oxidations. Nevertheless, despite there are some achievements, several aspects are still
not solved for an industrial applicability, as the selectivity to partial oxidation products. This
paper will present an overview on the synthesis, characterization and catalytic behaviour of
multicomponent metal oxides, with special attention to metal oxidic bronzes and molecular
sieves, as active and selective catalysts for the gas phase partial oxidation of hydrocarbons.
Recent examples on the new synthetic procedures and new structures will be also discussed.
Introduction
The selective oxidative functionalization of short chain paraffins is a formidable challenge for the
sustainable use of alkanes as feedstock and has attracted special attention during the last two
decades [1]. Two strategies have been mainly developed in alkane oxidation: i) the oxidative
dehydrogenation to achieve olefins and ii) the direct oxidation of alkanes to O- or N-containing
products. However, only the oxidation of n-butane to maleic anhydride is industrially applied.
The oxidative dehydrogenation of short chain alkanes has been extensively studied because it
is a very attractive way for alkane functionalization. Mixed metal oxides and metal containing
molecular sieves have been proposed as active and relatively selective catalysts in the
activation of alkanes. Although the use of N2O rather than oxygen could improve the selectivity
to olefins, these catalysts cannot be considered as competitor of steam cracking technologies.
Only a few catalytic systems for ethane oxydehydrogenation could have some interest from an
industrial point of view.
The second way for the functionalization of alkanes could be to replace olefins by alkane due to
its low cost. Although a first approach could be to integrate a first dehydrogenation reactor to
the conventional olefin oxidation process, the research effort in the last years is being carried
out towards the direct oxidation (in one stage) of propane since this could permit the reduction
of the reaction steps.
Multicomponent mixed metal oxides, MoVTe(Sb)NbO catalysts, reported by Mitsubishi in the
early 1990s, seem to be promising in the (amm)oxidation of propane [2] and in the oxidative
dehydrogenation of ethane to ethylene [3].
Typically, the most efficient MoVTe(Sb)NbO catalysts present at least two crystalline phases [4,
5]: (i) an orthorhombic (AO)2−2x(A2O)nM20O56 (A = Te or Sb and M =Mo, V, Nb), the so-called M1
(isostructural with Csx(Nb,W)5O14) and (ii) an orthorhombically distorted Te0.33MO3.33 or
(Sb2O)M6O19 phase (M = Mo, V, Nb), the so-called M2. In addition, TeMo5O16 (or Sb4Mo10Ox),
(V,Nb)-containing Mo5O14, and/or tetragonal bronzes may be present, depending on the catalyst
composition and the catalyst preparation procedure. However, the M1 phase itself seems to be
active and selective on the partial oxidation of propane and ethane, while M2 is only active and
selective in the oxidation of propene to acrolein and/or acrylic acid. A certain composition range
seems to be necessary to achieve the best catalytic performance, since the formation of
Te2M20O57-type phase strongly depends on both the catalyst composition and the catalyst
preparation method, post-synthesis treatment should be also considered in order to prepare
effective catalysts [5]. The reported results suggest a molecular structure-performance
relationship at the surface of functional materials [4].
19
K1
On the other hand, the different catalytic behaviour of these phases can be explained on the
basis of crystal structure, MO6 octahedra form pentagonal, hexagonal and heptagonal channels
in M1-phase and only hexagonal channels in M2-phase. More recently, new oxidic bronzes and
4+
synthesis strategies have been proposed. A0.5[Mo5-a-bVa XbO14] (A = Rb, Cs, X = no element,
Nb, Ta,W, Sb, Bi, Se, Te) with a M1-type structure [6], PMo(W)VNbO mixed oxides with a
tetragonal tungsten bronze structure (TTB) [7], or new synthesis procedures in the preparation
of other Mo-bronzes [8], or Nb,Mo-containing mesoporous materials [9] have been reported, in
which a clear structure-behaviour relationship can also be proposed.
Recently it has been proposed that some of these structures should be considered as
microporous materials [10] and their catalytic performance is discussed in terms not only of the
chemical composition (bulk and surface) but also in terms of catalyst structure (including the
nature and size of channels in this type of materials).
Acknowledgments
Financial support was provided by the DGICYT of Spain (project CTQ2006-09358-BQU).
References
[1] J.M. López Nieto, Top. Catal. 41 (2006) 3.
[2] a) M. Hatano, A. Kayo. EP 318285B1 (1988); b) T. Ushikubo, K. Oshima, A. Kayou, A, T. Umezawa, K. Kiyono, I.
Sawaki, EP529853 A2 (1993).
[3] a) J.M. López Nieto, P. Botella, M.I. Vázquez, A. Dejoz, WO Pat 0346035 (2003); b) J.M. López Nieto, P. Botella,
M.I. Vázquez, A. Dejoz, Chem. Commun. (2002) 1906.
[4] a) J.M.M. Millet, H. Roussel, A. Pigamo, J.L. Dubois, J.C. Jumas, Appl. Catal. A: Gen. 232 (2002) 77; b) H. Tsuji, K.
Oshima, Y. Koyasu, Chem Mater. 15 (2003) 2112; c) P. DeSanto, D.J. Buttrey, R.K. Grasselli, C.G. Lugmair, A.F.
Volpe, B.H.Toby, Topics Catal. 23 (2003) 23.
[5] a) P. Botella, E. García-González, J.M. López Nieto, J.M. González-Calbet, Solid State Sciences 7 (2005) 507; b)
A.C Sanfiz, T.W. Hansen, A. Sakthivel, A. Trunschke , R. Schlogl, A. Knoester, H.H. Brongersma, M.H. Looi, S.B.A.
Hamid, J. Catal. 258 (2008) 35.
[5] F. Ivars, B. Solsona, E. Rodríguez-Castellón, J.M. López Nieto J. Catal. 262 (2009) 35.
[6] H. Hibst, F. Rosowski, G. Cox, Catal. Today 117 (2006) 234.
[7] P. Botella, B. Solsona, E. García-González, J:M. M. González-Calbet, J.M. López Nieto, Chem Comm. (2007) 5040.
[8] a) M. Sadakane,N. Watanabe, T. Katou, Y. Nodasaka, W. Ueda, Angew. Chem. Int. Ed. 46 (2007) 1493; b) N. R.
Shiju, V.V. Guliants, ChemPhysChem 8 (2007) 1615.
[9] L. Yuan, S. Bhatt, G. Beaucage, V.V. Guliants, S. Mamedov, R.S. Soman J. Phys. Chem. B, 109 (2005) 23250.
[10] M. Sadakane, K. Kodato, T. Kuranishi, Y. Nodasaka,K. Sugawara, N. Sakaguchi, T. Nagai, Y. Matsui, W. Ueda,
Angew. Chem. Int. Ed. 47 (2008) 2493.
20
K2
Microporous and Mesoporous Materials
Venčeslav Kaučič
National Institute of Chemistry and University of Ljubljana, Hajdrihova 19, 1000 Ljubljana,
Slovenia
Summary
Transition metal-modified microporous zeolitic materials (silicate- and phosphate-based) are
attractive catalysts due to their hydrothermal stability and high catalytic activity and selectivity.
Metal-modified mesoporous materials with larger pore openings have been developed for
catalytic processes where larger molecules are involved. The inclusion of nanosized particles of
zeolitic microporous materials with larger external surface areas and high surface activity into
mesoporous matrices, i.e. the preparation of microporous/mesoporous composites,
substantially enhances the catalytic activity of mesoporous materials. The important feature of
nanoporous solids based on various metal oxides is also their ability to form thin films with
nanometer-scale thickness. Examples of successful preparation and/or functionalisation of new
nanoporous solids encompass microporous and mesoporous silicates (MnS-1, MnMCM-41,
MnTUD-1), microporous and mesoporous aluminophosphates (FeAPO-36, FeHMA),
microporous/mesoporous silicate composites ((Ti,Al)-Beta/MCM-41, (Ti,Al)-Beta/MCM-48, TiBeta/SBA-15) as well as cubic mesoporous aluminophosphate thin films. Studies of structureproperty relations of new solids have included X-ray diffraction, spectroscopic (XAS, NMR) and
electron microscopy characterisation techniques.
Porous materials are classified into three categories, microporous with pore openings from 0.3
to 2 nm, mesoporous having pores between 2 and 50 nm, and macroporous with pores greater
than 50 nm. Microporous materials are exemplified by crystalline framework solids such as
zeolites (aluminosilicates), whose crystal structure defines channels and cages, i.e. micropores,
of strictly regular dimensions. Mesoporous materials, exemplified by the silicate MS41 materials
family, are amorphous solids exhibiting highly-ordered pore structures and large internal surface
areas.
Microporous materials are generally prepared hydrothermally from aqueous gels containing a
source of the framework building elements (Si, Al, P, etc.), a mineraliser (OH-, F-) regulating the
dissolution/condensation processes during the crystallization, and a structure-directing agent,
usually an organic amine or ammonium salt. Transition metals can be incorporated into
microporous or mesoporous materials by a post-synthetic ion-exchange treatment or by direct
framework substitution by the addition of transition metal cations into the synthesis gel.
An alternative to a classical hydrothermal synthesis is a microwave oven. The microwave
heating is regarded as a novel synthesis tool for microporous and mesoporous materials
because it offers several benefits, such as homogeneous nucleation, the promotion of faster
crystallisation, rapid synthesis, the formation of uniform crystals, and small crystallites, facile
morphology control, the avoidance of undesirable phases by shortening the synthesis time and
so on. Recently, it was found that it provides an effective way to control the particle size
distribution, crystal morphology, orientation, and even the crystalline phase.
Microporous materials are mostly used as heterogeneous acid- and redox catalysts in
petroleum industry and in the production of chemicals for various types of shape-selective
conversion and separation reactions. The most common reactions, where microporous acidcatalysts are involved, are fluid catalytic cracking, hydrocracking, aliphate alkylation,
isomerisation, transformation of aromatics and the conversion of methanol to hydrocarbons.
Redox microporous catalysts are also increasingly used for a variety of selective oxidations of
various substrates of synthetic hydrocarbons, alcohols, and amines since these reactions can
be performed under mild conditions in the liquid phase. An illustrative example is the clean
production of adipic acid that is used in the production of nylon with the direct oxidation of
cyclohexene with aqueous H2O2 using Ti- or Fe-substituted microporous catalysts. The
discovery of mesoporous silicates attracted worldwide attention since they can incorporate
relatively large-sized species inside the pores. The extensive research to expand their
21
K2
functionality and improve their hydrothermal and chemical stability by modified and optimised
synthetic or post-synthetic routes in recent years has already enabled their application in the
field of catalysis. Intensive research efforts have also been driven by the emerging applications
such as biosensors, drug delivery, gas separation, energy storage and fuel cell technologies.
Investigations in the filed of mesoporous thin films are uprising fast due to their potential
applications as chemical and optical sensors, shape-selective membranes and energy-storage
devices.
The incorporation of transition metals into silicate, aluminophosphate and similar inorganic
frameworks generates or moderates catalytic activity of the materials. Here we report on
synthesis and structural studies of new micro- and mesoporous materials with the emphasis on
the preparation of metal-modified nanosized zeolitic particles, microporous/mesoporous
composites and zeolitic thin films.The elucidation of structures of ordered porous materials is
essential for the understanding and prediction of their macroscopic physical and chemical
properties. In particular, the size and connectivity of the pores determine their molecular sieving
capability. The coordination, location, oxidation state and strength of bonding of the divalent and
other transition metal ions in materials are directly related to their activity/selectivity in catalytic
and other reactions.
The conventional single-crystal and powder diffraction methods have been successfully used for
structure determinations of crystalline microporous structures. Problems that can arise are
mainly due to the small size of the crystallites that often require ab initio powder structure
solutions and the low concentration and/or random distribution of metal active sites over the
framework or extra-framework positions. The rapid development of synchrotron radiation
sources has brought around a tremendous progress in XRD techniques and methods, e.g.
anomalous dispersion methods for metal site determination. With the availability of synchrotron
radiation sources, X-ray absorption spectroscopy (XAS) techniques have also developed into a
widely used tool for structural research of ordered porous materials. XAS analytical methods
XANES and EXAFS provide structural information about local symmetry and the average
oxidation number of selected atom. Since XAS is selective towards a particular element and
sensitive only towards a short-range order, it is one of the most appropriate spectroscopic tools
for microporous and mesoporous catalysts characterization. Combining in situ XRD and XAS is
an excellent approach to obtain information on reaction-dependent changes of both long-range
crystallographic order (XRD) as well as oxidation state and local coordination environment of
particular elements (XAS) in a solid catalyst.
Nuclear magnetic resonance spectroscopy also offers a wealth of information on structural and
dynamical properties of crystalline- as well as amorphous porous materials. The positions and
local environments of framework and extra-framework atoms of porous solids can be
29
27
31
69
71
determined by either studying NMR spectra of Si, Al, P, Ga or Ga nuclei, or nuclei of
1
23
7
133
charge-compensating ions like H, Na, Li or Cs.
22
K3
Carbon powder as conducting supports for electrocatalysts in low temperature fuel cells
Jean-Michel LEGER
Laboratory of Organic Chemistry (LACCO), CNRS-University of Poitiers,
40 Avenue du Recteur Pineau, 86000 Poitiers France
[email protected]
Proton Exchange Fuel Cells (PEMFC) are now considered as the most convenient fuel cells for
application in a large range of power densities. Applications from micro fuel cells (electronic
devices) mid-sized fuel cells to automotive applications are scheduled in the future. However,
PEMFC, which work at low temperatures (from room temperature to 100 °C) and in acidic
environment (protonic electrolytic membrane) need the development of convenient
electrocatalysts. This means catalysts leading to acceptable performances (kinetically speaking)
and with a good stability with time.
Suitable catalysts are generally noble metals, mainly platinum, possibly modified by other
metals or oxides. Due to the costs of platinum, it is obvious that the total amount of noble metal
need to be limited for large scale applications. An electrocatalytic reaction is a reaction taking
place at the catalyst (electrode) surface. Then the only way to increase the overall rate of the
reaction is to increase the active surface of the catalyst. This can be obtained by decreasing the
size of the metallic particles of the catalysts. The key problem is then to have an optimized
utilization of these particles and it is one of the key roles of the supporting material used in the
construction of electrode for fuel cells.
Carbon is actually the unique conducting material used for this application, even if some other
alternative are explored, for example with oxides. The main key property of the carbon powder
for fuel cell is the electrical conductivity. Different preparation procedures are proposed to
increase it before the preparation of the catalytic layer itself. The second key point concerns the
ability of the catalytic particle to be fixed on the carbon powder surface. This is important to
have the highest possible utilization of the catalyst (agglomeration of particles should be limited
for example), but also if we considered the stability with time. If the mobility of particle is too high
at the carbon surface, fritting and agglomeration of metallic particles occur leading to a
decrease of the active area and of the performances of the fuel cell.
Another problem concerns the chemical degradation of the carbon materials under the working
conditions. The presence of a catalyst such as platinum and of oxygen (cathodic side) can lead
to the chemical oxidation of carbon (to produce CO2). This is observed during long term
experiment with significant degradation of the carbon layer and consequently migration of
platinum particles though the electrolytic membrane.
The purpose of this keynote lecture is to discuss of these different points in relation with the use
of carbon powder as supporting materials for catalysts in fuel cells. Several examples of the
preparation of electrocatalysts and how to put and maintain them at the carbon powder surface
will be given. It is important to understand that the preparation procedures are critical. These
techniques can be purely chemical (colloidal precursors; micro-emulsion…), electrochemical
(electrodeposition…), physical (plasma…). The pretreatment of the carbon powder is also a key
point, mainly for the optimization of the utilization of the catalyst. It consist mainly developing
procedures to increase the concentration of oxidized sites at the carbon powder surface. These
sites allow then a strong interaction with the metallic particles and limit their mobility.
Even if some people from fuel cell development still consider that carbon supporting materials
are only a secondary problem, less essential than catalyst or membrane for example, it is
obvious that the interactions between catalysts and carbon are extremely important. The best
catalyst not stabilized at the carbon surface leads always to low performances.
23
K3
References
[1] C. Lamy, J-M. Léger , S. Srinivasan, Direct Methanol Fuel Cells: From a 20th Century Electrochemist's Dream to a
21st Century Emerging Technology, in Modern Aspects of Electrochemistry, J'O.M. Bockris, B. E. Conway and R. White
(Eds), Kluwer Academic/Plenum Publishers (New-York), vol. 34, (2001) p 53-118.
[2] J-M. Léger, C. Coutanceau, C. Lamy, Electrocatalysis for Direct Alcohol Fuel Cell, in “Fuel Cell Catalysis: a surface
science approach”, M.T.M. Koper (Ed), J. Wiley & Sons, New Jersey, chap 11 (2009) 343-373.
[3] C. Coutanceau, S. Brimaud, C. Lamy, J.-M. Léger, L. Dubau, S. Rousseau, F. Vigier, Review of different methods for
developing Nanoelelectrocatalysts for the oxidation of organic compounds, Electrochim. Acta, 53 (2008) 6865.
[4] C. Grolleau, C. Coutanceau, F. Pierre, J.M. Léger, Effect of potential cycling on structure and activity of Pt
nanoparticles dispersed on different carbon supports, Electrochim. Acta, 53 (2008) 7157.
[5] P. Brault, S. Roualdes, A. Caillard, A.-L. Thomann, J. Mathias, J. Durand, C. Coutanceau, J.-M.Leger,C. Charles R.
Boswell,Solid polymer fuel cell synthesis by low pressure plasmas: a short review, Eur. Phys. J. Appl. Phys. 34 (2006)
151.
24
NMR of physisorbed
K4
129
Xe used as a probe to investigate porous solids
Jacques Fraissard
University P. and M. Curie, ESPCI, Laboratory ˝ Physique Quantique˝,
10 rue Vauquelin, 75231 Paris, France
The fundamental idea was to find a chemically inert molecule, detectable by NMR and
particularly sensitive to physical interactions with other species, which could be used as a probe
to determine the properties of its environment [1]. The 129 xenon isotope is this ideal probe.
Chemical shifts and relaxation times of xenon are solely affected by intermolecular interactions
and are exquisitely sensitive to the atom’s surrounding. This sensitivity to its environment
means that the Xe nucleus can report on a wide variety of attributes of the physical systems in
which it finds itself: gas, liquids, cages in a zeolite, nanochannels in a molecular solid,
clathrates, proteins in solution, amorphous polymers, etc. It can be used also for imaging and
gas diffusion measurements. Several reviews have been published on these applications [2-3].
By using optical polarization techniques [4] the sensitivity of detection can be increased by
several orders of magnitude and is particularly useful for several studies (porous materials,
microimaging, polymers and elastomers, etc.).
We will present some examples of the applications of the Xe-NMR technique to the
characterization of microporous and mesoporous solids, including carbon nanotubes. We will
add also few words about the characterization of solid polymers and proteins interactions.
References
[1] T. Ito and J. Fraissard, Proceedings of the 5th International Zeolite Conference, Naples, 1980 L.V.C. Rees (ed.),
Heyden, London, 1980, p. 510.
[2] D. Raftery, B.F. Chmelka, NMR Basic Principles and Progress. B. Blümich, Ed ; Springer-verlag, Berlin, Heidelberg,
30 (1994) 111.
[3] J.L. Bonardet, J. Fraissard, A. Gedeon, M.A. Springuel-Huet, Catal.Rev.-Sci.Eng., 41(2) (1999) 115.
[4] D. Raftery, H. Long, T. Meersmann, P.J. Grandinetti, L. Revey and A. Pines, Phys. Rev.Lett.,66 (1991) 584.
25
K4
26
BOOK OF ABSTRACTS
Section III: Oral
Communications
O1
The effect of porosity of niobosilicate supports and VSbOx loading on the ammoxidation
of propane
a,b
a
a
b,*
a
H. Golinska , E. Rojas , R. Lopez-Medina , M. Ziolek , Miguel A. Bañares ,
c,*
M.O. Guerrero-Pérez
a
Catalytic Spectroscopy Laboratory, Instituto de Catálisis y Petroleoquímica; CSIC; Marie Curie
b
2; E-29049-Madrid (Spain); Adam Mickiewicz University, Faculty of Chemistry, Grunwaldzka 6,
c
60-780 Poznan, Poland; Departamento de Ingeniería Química. Universidad de Málaga; E29071-Málaga (Spain)
Introduction
Vanadium-antimony oxides are well known as catalysts for selective oxidation and
ammoxidation reactions [1,2]. The activity and selectivity of catalysts in these processes are
greatly dependent on the loading (Sb:V atomic ratio), method of preparation, gas phase
composition during the thermal treatment, and the nature of the support [3]. Moreover, the role
of the nature of antimony complex used during the preparation of the catalysts was stressed
[4,5]. Sb-V-Ox catalysts with an excess of V are highly active and selective for propane
oxidative dehydrogenation while an excess of Sb affords Sb-V-Ox catalyst more efficient for
propane ammoxidation [6,7].
The idea of this work was to use niobosilicate supports exhibiting different porosity (mesopores
or macropores) as supports for VsbOx binary oxides introduced with step by step impregnation.
The effect of porosity, vanadium-antimony oxides loading, and the sequence of the
impregnation (first vanadium next antimony or reverse) on the effectivness in ammoxidation of
propane has been studied.
Experimental
Two niobosilicate supports were synthesized: mesoporous NbMCM-41 (denoted NbM;
Si/Nb=64) and macroporous SiNbOx. They were impregnated stepwise with antimony and
vanadium precursors (NH4VO3 – BDH Chemicals Ltd. And (CH3COO)3Sb – Aldrich) using V/Sb
atomic ratios of 1 or 0.5. and ~25 wt % of Sb. The other group of materials were prepared by
the sequenced impregnation starting from vanadium and next antimony sources, and with the
atomic excess of vanadium (3 wt % of Sb and 1.5 wt % of V). The samples used in the
ammoxidation reactions and their texture parameters estimated by XRD and nitrogen
adsorption, are shown in Table 1. The gas phase ammoxidation of propane in the temperature
range of 623 – 773 K was studied on the prepared catalysts, which were characterized before
and after reactions with Raman spectroscopy.
Results and discussion
The pristine NbMCM-41 material exhibits very well ordered hexagonal arrangement of
2
mesopores of 2.2 nm diameter and high pore volume and surface area of ~1000 m /g estimated
from XRD and nitrogen adsorption measurements. The data in Table 1 show that the use of
high loading of binary SbV oxides almost totally block mesopores in NbMCM-41 ordered
mesoporous material and causes the dramatically decrease of the surface area and pore
3
volume. The use of macroporous niobiosilica allow to leave 0.3 cm /g free pore volume in the
catalyst after VsbOx loading. These texture parameters determine the catalytic activity and
selectivity in ammoxidation of propane (Table 2). The catalytic tests for acidity and basicity
indicated that 0.5VSb/SiNbOx reveals lower acidity than 0.5VSb/NbM with the same oxides
loading. This feature together with texture parameters cause a very high selectivity in the
formation of acrylonitrile on 0.5VSb/SiNbOx catalyst.
29
O1
Table 1. Composition of the catalysts and texture parameters
-
-
-
1006
Pore
volume
BJH,
3
cm /g
1.1
0.8
2
3
25
1.5
5
885
52
1.0
0.1
1VSb/NbM
1
25
10
27
0.07
SiNbOx
0.5VSb/SiNbOx
2
25
5
165
92
0.9
0.3
Catalysts*
NbM
0.12Sb0.15V/NbM
0.5VSb/NbM
Sb/V
atom.
Ratio
% wt.
Of Sb
% wt.
Of V
BET
area,
2
m /g
The order of V and Sb in the
symbol of catalysts indicates
the
sequence
of
impregnation (e.g. SbV/M
means the first vanadium
was loaded and next
antimony)
Table 2 . The results of ammoxidation af propene at 773 K
Selectivity (%)
Catalyst
NbM
0.12Sb0.15V/NbM
0.5VSb/NbM
1VSb/NbM
0.5VSb/SiNbOx
Propane
conversion
(%)
acrylonitrile
3.0
4.4
17.8
18.6
11.4
14.9
14.1
29.2
20.7
69.7
acetoni
trile
63.6
25.6
37.8
38.3
11.7
acroleine
0
0.3
9.4
3.0
0.1
propen
e
20.2
58.9
19.8
20.3
16.3
ethene
Cox
0
0
0
0
1.1
1.4
1.1
3.8
17.7
1.1
Taking into account the results of catalytic activity and TEM, SEM, XRD, Raman spectroscopy
study one could define the following conclusions from this work.
• NbMCM-41 as support for Sb-V-Ox phase interacts strongly with vanadium when a low
loading of V (1.5 wt.%) is used and vanadium is the first component introduced during
the stepwise impregnation.
• The higher loading of antimony and vanadium (25 and 5 wt.% respectively) results in
the formation of needle/stake Sb0.95V0.95O4 rutile crystals; the increase of vanadium
content to 10 wt.% gives rise to the domination of plate shaped SbxVyO5 phase.
• The mesopores in NbMCM-41 modified by the high loading of Sb-V-Ox phases are
almost completely blocked by the bimetallic oxides.
• The use of macroporous SiNbOx as the support for VsbOx phase leads to the higher
selectivity in the formation of acrylonitrile.
Acknowledgements
COST action D36, WG No D36/0006/06, the Polish Ministry of Science (Grant No.
118/COS/2007/03) and . Spanish Ministry of Science and Innovation (CTQ2008/02461/PPQ)
are acknowledged for the financial support
References
[1] R. K. Grasselli, Catal. Today 49 (1999) 141.
[2] S. Larrondo, B. Irigoyen, G. Baronetti, N. Amadeo, Appl. Catal. A, 250 (2003) 279.
[3] G. Centi, S. Perathoner, F. Trifiro, Appl. Catal. A, 157 (1997).
[4] M.O. Guerrero-Perez, M.A. Banares, Catal. Today 96 (2004) 265.
[5] M.O. Guerrero-Perez, J.L. G. Fierro, M.A. Banares, Top. Catal. 41 (2006) 43.
[6] M.O. Guerrero-Perez, J.L. G. Fierro, M.A. Banares, Catal. Today 78 (2003) 387.
30
O2
Towards 4-way catalysis
James A Sullivan
UCD School of Chemistry and Chemical Biology, Belfield, Dublin 4, Ireland.
[email protected]
Nox and Particulate Matter (PM) remain the two most intractable emissions from diesel engines
and a goal of the automotive industry is to combine strategies for their removal into a single
catalytic bed. Nox is a primary and secondary pollutant contributing directly to acid rain and
causing respiratory problems while contributing indirectly to photochemical smog [1]. PM
defaces urban environments, carry possible carcinogens that can lodge in the alveoli of the lung
and contribute to global warming (through the reduction of the albedo of arctic ice) [2].
For the past 20 years emissions from gasoline powered vehicles have been deNOxed through
reduction of Nox to N2 through reduction with CO and unburned hydrocarbons (HC) present in
the exhaust mixture [3]. On diesel engines the net concentration of oxidants (NO / O2) is
significantly greater than that of reductants (CO/ HC) and standard three way catalysts are
unable to reduce Nox so other control strategies are required [4]. The most common and
effective is the Nox Storage and Reduction (NSR) system in which NO is oxidised to NO2 over a
Pt catalyst and subsequently this is stored on a Nox storage material (BaO) as a nitrate
(Ba(NO3)2). Once the Nox trap is saturated, a pulse of hydrocarbons regenerates it, releasing
and reducing NO2 and restarts the cycle [5].
Regarding PM control technologies, the current after-treatment system relies on a particulate
filter which strains larger particles from the stream followed by oxidation either with O2 through a
brief high temperature excursion or with NO2 (through a C(s) + NO2 CO + NO reaction) [6].
In systems where NO2 is used to combust the particulates a Pt catalyst is added to the
formulation in order to catalyse NO (which is present in the exhaust mixture) oxidation to NO2.
Note that this is the same first step that operates in the NSR system described above and
therefore the combination of these two systems into one catalytic bed is a possibility. Such a
combination would reduce the overall volume and mass of any after-treatment systems that a
diesel exhaust would require and this would have knock on effects on the fuel efficiency (and
therefore the CO2 emissions per km travelled) of the vehicle. Recently promotions in soot
combustion have been reported in the presence of a Nox trap [7].
In the current work we have studied combinations of Nox trapping materials and Model PM in
order to determine the mechanism of this reported promotional effect and we have also studied
the effects of PM on the efficiency of a Nox trap. In the former case we have determined that
the localised transient increase in NO2(g) upon periodic regeneration of the trap causes the
promotional effect upon soot combustion [8] while in the latter case we have, using temperature
programmed techniques, transient kinetic analysis and in-situ FTIR, demonstrated that the
presence of PM decreases the efficiency of a Nox trap.
The reason for the latter finding is a competition between the NO2 generated over Pt sites. In an
NSR system this should adsorb on (and react with) the NOx trapping component to generate a
surface nitrate. However, in the presence of PM the NO2 is reduced to NO (in the process of
combusting PM) which cannot be trapped by the Nox storage component.
This confirms that in an NSR system there is significant mobility in the NO2 generated through
NO oxidation which in turn suggests that the contact between the NO oxidation component and
the Nox trapping component of such systems is not crucial.
References
[1] W. Kenneth, C.F. Warner, “Air Pollution, its origin and control” Harper and Row Publishers Inc. 1976
[2] J. Hansen, L. Nazarenko, Proc. Natl. Acad. Sci. 101 (2004) 423–428.
[3] K.C. Taylor, Catal. Rev. Sci. Eng., 35, (4), 457, 1993.TWC
[4] K.C. Taylor, Cat. Sci. and Tech., Anderson, J.R., Boudart, M., Ed., Springer-Verlag, 5, (1984).
[5] S. Poulston, R.R. Rajaram, Catal. Today 81 (2003) 603.
[6] A.P. Walker, Top. Catal. 28 (1–4) (2004) 165–170.
[7] F. Jacquot, J.-F. Brilhac, P. Phillips, at the 4th International Conference on Environmental Catalysis, Heidleberg,
June, 2005
[8] JA Sullivan, O Keane, and A Cassidy, Applied Catalysis B: Environmental 75 (2007) 102–106.
31
O2
32
O3
Towards an optimization of MoVNbTe-catalysts for C3-oxidation
G. Mestl
Süd-Chemie AG
Propylene is one of the key building block petrochemicals used as feedstock for a variety of
polymers and intermediates. Mayjor propylene derivatives include polypropylene, acrylonitrile,
propylene oxide, cumene/phenol, oxo alcohols, acrylic acid, oligomers, and other miscellaneous
intermediates used, in turn in a wide range of end-use applications including automotive,
construction, consumer durables, packaging, and electronics. The global propylene demand
grew form 16,4 million tons in 1980 to around 30 million tons in 1990, corresponding to an
average annual growth of 6,2 percent. In the decade ending in 2000, the demand grew at an
average rate of 5,7 percent per year, reaching 52 million tons. Now at the end of this decade,
the propylene demand has reached about 81 million tons at a growth rate of about 5,3 percent
per annum. Driven by high polypropylene and other propylene derivative demand, propylene
growth rate will exceed ethylene growth rate (see Fig.1 [1]).
Based on announced cracker projects olefin expansions will fall short of increased propylene
demand for next few years. Future additions of predominately gas based crackers in Middle
East, motivated by low NGL prices will reduce worldwide average of propylene yield from steam
cracking even further. Hence, propylene demand will remain strong. There will be an imbalance
between ethylene and propylene growth rate creating a propylene supply gap. The Asian gap
between supply and demand is substantial and is causing very strong propylene pricing.
The acrylic acid, currently produced from propylene in a two step process, demand showed an
annual growth of 4% through 2005 and the demand for acrylic acid is forecast to increase four
percent per annum. Acrylate esters such as butyl, ethyl, ethylhexyl and methyl acrylates
account for the majority of acrylic acid demand. These products are utilized as the acrylic
monomer component in a variety of coatings, adhesives, paper and leather finishes and as comonomers and property modifiers in plastics production. Gains will thus be stimulated by growth
in demand for these end-use products, in particular industrial and specialty coatings, paper
finishes and plastics additives. The producers are expected to focus their attention on the
production of higher growth specialty acrylates (such as ethylene methyl acrylate); and acrylic
acid polymers. The latter include superabsorbent polymers (SAPs) used in baby diapers, adult
incontinence products and feminine hygiene products; water treatment polymers and detergent
additives. Growth in acrylic acid demand necessitate plant expansions throughout the coming
decade, strong demand for derivatives has led to very tight acrylic acid supplies on several
occasions.
33
O3
This increase in propylene demand (vide supra) and its derivatives, like acrylic acid, hence
implied an increasing price gap to the cheaper propane in the past, rendering processes based
on propane feedstock economically more viable. This expected price gap between propylene
and propane promoted heavy R&D on new catalysts for the direct conversion of propane to
acrylic acid during the last 20 years both in industry and academia.
Propane as such is not produced for the sake of its own it is a by-product of two other
processes, natural gas, where propane (and butane) has to be extracted, and petroleum
refining, where it is produced in the steam cracker. Hence, the volume of propane made
available from natural gas processing and oil refining cannot be adjusted when prices and/or
demand for propane fluctuate.
The main uses of propane areas follows [2]. About 38 percent of the propane consumed in the
U. S. is used in the petrochemical industry. Residential and commercial use accounts for about
45 percent of all propane used most commonly to provide energy to areas not serviced by the
natural gas distribution system. Farm or agricultural uses of propane, 7% of demand, include
crop drying, weed control, and fuel for farm equipment and irrigation pumps. Industrial use of
propane, the fourth largest propane-consuming sector, 7%, include space heating, soldering,
cutting, heat treating, etc.
The demand of natural gas [3], i.e. propane, in the US, as an example, increased and will
continue to increase while its production remained nearly constant, driving the propane prices
upwards.
As fact, the price gap between propylene and propane did not open up as expected 20 years
ago. Hence, analysts expect that the next generation acrylic acid plants will convert propylene in
one step to acrylic acid instead of the current two-reactor technology, the economic realization
of the propane based, 1-step process is shifted into farther future. However, it still should be
further investigated for the coming post crude oil times.
References
[1] G.M. Intille, Asia Petrochemical Industry Conference, Yokohama, Japan, 2005
[2] Energy Information Administration, DOE.
[3] GSC Energy, Energy Markets Outlook, Atlanta, 2005
34
O4
Silylation of titanium-containing amorphous silica catalyst: Effect on the alkenes
epoxidation with H2O2
*
M. C. Capel-Sanchez , J. M. Campos-Martin, J. L. G. Fierro
Instituto de Catálisis y Petroleoquímica, CSI,. c/Marie Curie, 2, Cantoblanco, 28049 Madrid.
Spain.
[email protected]
Introduction
Despite numerous reports in the literature, the epoxidation of terminal alkenes remains a
challenge in petrochemistry. Many different methods have been developed for the preparation
of epoxides. Among the non-zeolitic substrates, Ti–SiO2-supported catalysts remain prominent
for their effectiveness in the epoxidation of alkenes with organic hydroperoxides, though it is
generally believed that they do not effectively epoxidize alkenes with hydrogen peroxide.
Nevertheless, we have reported a very simple route for the preparation titanium-silica-supported
catalysts which are very active and selective in the epoxidation of alkenes with hydrogen
peroxide [1,2]. However, it has been reported that Ti-SiO2 samples show a lower intrinsic
activity and lower selectivity toward the use of H2O2 for alkene oxidation than either TS-1 or Ti-β
owing to their high hydrophilicity. It has been proposed that the hydrophilic/hydrophobic property
of Ti zeolites plays an important role in their activity for liquid phase oxidations [1]. We have
conducted silylation of Ti-SiO2 in order to enhance their activity in epoxidation with dilute H2O2
by increasing their hydrophobicity. Here, our objective is to improve the catalytic activity in the
epoxidation of alkenes with H2O2 by silylation of Ti-containing amorphous silica.
Experimental Methods
Catalysts were prepared as follows: titanium isopropoxide (Aldrich, reagent grade) (0.65 g) was
dispersed in 2-propanol (25 ml), the solution was heated to 353 K under stirring and then 5 g of
silica (Grace Davison, XPO 2407) were added and the suspension was stirred for 2 h. The solid
was filtered out and washed twice with 25 ml of 2-propanol, dried at 383 K, and finally calcined
at 773 K for 5 h. Two silylant reagents: 1,1,1,3,3,3-hexamethyldisilanaze (HMDS) and
tetramethyldisilazane (TMDS) were used for the silylation of the samples. The procedure was as
follows: the silylant reagent fed continuously by a syringe pump to a continuous flow of N2 on
the sample bed with a temperature of 473 K for 2 h, then a nitrogen flow was fed for 2 h. The
silylation reagent/catalyst ratio was of 0,23.
These solids were characterized by elemental analysis, DRS UV-Vis and X-ray photoelectron
spectroscopy (XPS) techniques. The catalysts were used in the epoxidation of 1-octene and
cyclohexene. In a typical run, a suspension of alkene (0.2 mol), tert-butanol (11 g) and 1 g of
catalyst was heated at 333 K, and then 4 g of an organic solution of 5 wt % of H2O2 (in 1 tbutanol) were added to the reaction vessel. The organic compounds were analysed by GC-FID
(Hewlett Packard 6890-plus, equipped with a HP-WAX capillary column). The hydrogen
peroxide was measured by standard iodometric titration.
Results and Conclusion
The elemental analysis (Table 1) shows a higher amount of carbon deposited on the catalyst
when TMDS is used. This observation indicates that silylation with TMDS is more effective than
HMDS. This observation can be due to the higher volume of trimethylsilane groups than
dimethylsilane. DRS UV-Vis spectra (Figure 1) of the samples are similar with only slight
differences. The silylated samples showed an absorption peak centered at 220 nm, typical of
isolated titanium in tetrahedral coordination [4]. The slight shift in band position and the increase
in bandwidth in the spectrum of reference sample point to distorted tetrahedral environment of
the titanium. Solid-state 29Si MAS-NMR (Figure 2) confirmed the presence of –SiCH3 groups
bound to the surface of the samples. Distinct resonances can be clearly distinguished for the
3
4
siloxane units [Q at ≈−104 ppm for Si(Osi)3(OH) units; Q at ≈−114 ppm for Si(Osi)4 units]. Only
4
3
two signals are observed (Q and Q ) on the nonsilylated catalyst. After silylation, a new signal
was detected at 12,5 ppm, which can be assigned to (CH3)3Si– (Osi) in the Cat-Sil-HMDS
35
O4
3
4
sample and at 20,5 assigned to (CH3)2SiH– (Osi) in the Cat-Sil-TMDS sample. The Q /Q ratio
(Table 1) in the reference Catalyst was estimated as 0.081. After silylation this ratio decreases.
The Cat-sil-TMDS sample exhibited the lowest ratio which indicates that the silylation coverage
in this sample is higher than in the Cat-Sil-HMDS one.
H
CH3
Si
Cat Reference
Cat-Sil-HMDS
Cat-Sil-TMDS
Cat-Sil-TMDS
H3 C
F (R)
CH3
O
CH3
Si
CH3
O
Cat-Sil-HMDS
Cat Reference
200
300
400
-140 -130 -120 -110 -100 -90
λ (nm)
Figure 1: DRS UV–vis spectra of samples
-30 -20 -10 0
10 20
δ (ppm)
Figure 2: 29Si CP-MAS NMR spectra of samples
under ambient conditions.
3
4
Table 1: Carbon and hydrogen composition and Q /Q ratio of samples
Cat Reference
Cat-Sil-HMDS
Cat-Sil-TMDS
3
4
%C
%H
Q /Q
1.85
2.20
0.73
0.86
0.081
0.045
0.039
The silylated samples showed higher conversion of hydrogen peroxide and selectivity to
epoxide than the original counterpart. This effect was more evident when higher concentration
of H2O2 was employed. This effect could be attributed to the higher hydrophobicity of silylated
sample. Silylation treatment of Ti/SiO2 catalysts enhances significantly the activity in the
expoxidation of alkenes with H2O2. The use of TMDS in the extend of the silylation is higher with
TMDS than with HMDS as a consequence of the smaller size of the former sylilating agent.
References
[1] M. C. Capel-Sanchez J. M. Campos-Martin, J. L. G. Fierro, M. P. de Frutos, A. Padilla Polo, Chem. iuse., (2000)
855-856
[2] M. C. Capel-Sanchez, J. M. Campos-Martin, and J. L. G. Fierro, J. Catal., 217 (2003) 195–202
[3] T. Tatsumi, K. A. Koyano and N. Igarashi, Chem. iuse., (1998) 325-326
[4] V. A. de la Peña O’Shea, M. C. Capel-Sanchez, G. Blanco-Brieva, J. M. Campos-Martin, J. L. G. Fierro, Angew.
Chem. Int. Ed. 42 (2003) 5851-5854
36
O5
Preferential oxidation of CO in H2 rich stream over gold catalysts supported on doped
ceria: effect of preparation method and dopants nature
1
2
1
2
1
L. Ilieva , G. Pantaleo , I. Ivanov , A. M. Venezia , D. Andreeva
1
Institute of Catalysis, BAS, “Acad. G. Bonchev” St., bl.11, 1113 Sofia, Bulgaria
Istituto per lo Studio di Materiali Nanostrutturati, CNR, I- 90146 Palermo, Italy
2
Introduction
The preferential oxidation of CO in H2-rich stream (PROX) is one of the most promising
approaches for the purification of hydrogen. The low temperature polymer electrolyte membrane
(PEM) fuel cells are extremely sensitive to trace of CO contamination. At the operating
o
temperature (80-100 C) the PROX catalysts have to be highly active as well as they need to be
highly selective, minimizing the loss of hydrogen by unwanted oxidation. Gold-based catalysts
are potentially capable of being effectively employed in fuel cells [1]. Schubert et al. [2] have
studied the effect of metal oxide support by comparing different Au catalysts. They have
established that Au/CeO2 represented the best compromise regarding the PROX activity,
selectivity and long term stability. Recently, a detailed study of PROX over Au on CeO2 doped
by Sm, La and Zn is given in Ref. [3].
The present investigation is focused on the comparison between the properties and the catalytic
performance in PROX over nanosized gold catalysts supported on doped ceria with nanodimensions. The ceria supports were modified by the addition of rare earth metals (RE=La, Sm,
Gd or Y), applying two different preparation methods: mechanochemical activation (MA) or coprecipitation (CP). The influence of the preparation techniques and the nature of the dopant on
the structure and catalytic activity are discussed.
Experimental
Two series of doped ceria supports were synthesized: (i) the supports were prepared by CP
from a solution of the corresponding metal nitrates in appropriate ratio with a solution of K2CO3;
(ii) a mixture of cerium hydroxide and the corresponding oxide of the dopant was subjected to
MA. Prior to gold deposition the mixed support was activated in a UV disintegrator. The amount
of Re2O3 modifier was 10 wt%. Gold (2 wt%) was introduced by deposition-precipitation method.
The catalysts were denoted as AuCeSm, AuCeGd, AuCeLa and AuCeY, CP or MA. AuCe
sample was used as a reference. The catalysts were characterized by XRD, HRTEM, HAADF,
TPR and Raman spectroscopy. The catalytic test was performed with feed gas: 1% CO, 70% H2
-1 -1
and 1% O2, WHSV=60 000 ml g h .
Results
The XRD results showed that MA catalysts are double phases, in addition to ceria, lines of the
oxides of dopants were also registered; the calculated values of lattice parameter of ceria
differed insignificantly. CP samples were single phases, the changes in ceria lattice parameters
more clearly depends on the ionic radius of the modifier. For both series of preparation the ceria
particles were nanosized with average particle size < 10 nm. A relatively higher number of
smaller gold particles were registered in MA samples compared to CP ones. However, there
were no big differences in the average size of gold depending on the dopant and the method of
-1
preparation. The main line of CeO2 dominates in the Raman spectra. A weak line at 548 cm ,
3+
assigned to the oxygen vacancies created by the presence of the Me modifiers was observed
only in the case of CP preparation method. It shows that a deeper modification of ceria
structure occurs. The values of the full width at the half of maximum (FWHM) of the main ceria
line were calculated. For both preparation methods the differences between the FWHM of AuCe
and gold catalysts on doped ceria were very significant. Since the average size of undoped and
doped ceria are in the same order, the observed widening can be connected to the formation of
oxygen vacancies in ceria structure. Different reasons could be responsible for the formation of
the oxygen vacancies in ceria. In the presence of nanogold particles, a strong modification of
3+
the ceria surface leading to Ce and neighbour oxygen vacancies has been already observed
3+
[4]. Supplementary oxygen vacancies are generated by modification of ceria on adding Me
37
O5
ions [5]. The latter are strongly dependent on the preparation method of the supports. In
agreement with these results for all gold catalysts supported on doped ceria the calculated H2
consumption for ceria surface layers reduction, estimated by TPR, was higher than that of AuCe
sample. However the H2 consumption for CP samples was lower compared to the
corresponding MA ones. These experimental results were unexpected. The eventual
explanation could be that the amount of oxygen vacancies in doped ceria, prepared by CP is
higher than that for the MA samples, however in the first case they are located preferentially
3+
around the Me dopant.
The PROX activities, expressed as degree of CO conversion and selectivity to CO2, are
compared in Fig. 1. It is seen that only AuCeSmMA catalysts exhibited higher activity and
selectivity than the AuCe sample. The modification of ceria with rare earths using CP leads to
higher activity and selectivity of the gold catalysts in respect to Au on undoped ceria. The
°
maxima in activity were observed in the interval of 80-100 C. Generally the CP catalysts are
more active and selective than the corresponding MA ones. Both the degree of CO conversion
and the selectivity to CO2 are the highest for AuCeYCP sample. This catalyst shows also very
o
good long term stability during the catalytic test at 100 C for 20 hs.
Figure 1. Catalytic activity and selectivity in PROX over studied gold catalysts: (A) – gold on undoped ceria and doped
ceria supports, prepared by MA; (B) – gold on undoped ceria and doped ceria supports, prepared by CP.
100
90
80
70
60
50
40
30
20
10
0
Conversion
Selectivity
AuCe
AuCe
AuCeGdMA
AuCeGdMA
AuCeSmMA
AuCeSmMA
AuCeLaMA
AuCeLaMA
(B)
Conversion/Selectivity, %
Conversion/Selectivity, %
(A)
0
50
100
150
T, 0C
200
250
300
Convertion
AuCe
AuCeYCP
AuCeSmCP
AuCeGdCP
AuCeLaCP
100
90
80
70
60
50
40
30
20
10
0
0
50
100
150
T, 0C
200
Selectivity
AuCe
AuCeYCP
AuCeSmCP
AuCeGdCP
AuCeLaCP
250
300
Conclusions
Gold catalysts supported on ceria doped by rare earth metals were synthesized by different
methods and studied in the PROX reaction. It was established that catalysts prepared by coprecipitation were more active and selective than samples made by mechanochemical
activation. A CP gold catalyst on yttrium-modified ceria exhibited the highest catalytic activity
and selectivity, and high stability. In the studied catalysts, the average sizes of gold and ceria
nanoparticles were of the same order. The most possible explanation should be associated with
the influence of the preparation method and the nature of dopants applied.
Acknowledgements
This study was performed in the frame of the D36/003/06 COST program. L. I. and D. A.
acknowledge the support by National Science Fund, MES of Bulgaria (project ТК-Х-1709). RZ
acknowledges PUNTA (IMPULSA 01), PAPIIT IN106507 and CONACYT 55154 project for the
financial support.
References
[1] D. Cameron, R. Holliday, D. Thompson, J. Power Sources 118 (2003) 298 and ref. therein.
[2] M.M. Schubert, V. Pizak, J. Garche, R.J. Behm, Catal. Lett. 76 (2001) 143.
[3] G. Avgouropoulos, M. Manzoli, F. Boccuzzi, T. Tabakova et al, J. Catal. 256 (2008) 237.
[4] T. Tabakova, F. Boccuzzi, M. Manzoli, D. Andreeva, Appl. Catal. A: Gen. 252 (2003) 385.
[5] A. Trovarelli, Catal. Rev. Sci. Eng. 38 (1996) 439.
38
O6
The Design of Metal-Single site Catalysts for their Application in Catalytic and
Photocatalytic Processes
a*
b
b
c
Stanislaw Dzwigaj , Jean-Philippe Nogier , Yannick Millot , Tetsuya Shishido,
a
Christophe Méthivier and Michel Che
a
UPMC Univ. Paris 6, CNRS, UMR 7197, Laboratoire de Réactivité de Surface, 4 Place
Jussieu, 75252 Paris Cedex 05, France,
b
UPMC Univ. Paris 6, CNRS, UMR 7142, Laboratoire des Systèmes Interfaciaux à l’Echelle
Nanométrique, 4 Place Jussieu, 75252 Paris Cedex 05, France
c
Kyoto University, Department of Molecular Engineering, Kyoto, 615-8510, Japan
*
[email protected]
Isolated tetrahedral Ti atoms at zeolite framework sites are considered to be active sites of both
catalytic and photocatalytic processes [1,2]. Therefore, the incorporation of transition metal ions
into the zeolite framework appears to be the important task. We were shown [3,4] that the
incorporation of transition metal ions into the lattice T-atom sites of BEA zeolite is strongly
favored when, in the first step, BEA is dealuminated by treatment by nitric acid solution and
then, in the second step, the incorporation of transition metal ions results from the reaction
between the cationic metal species of the precursor solution and the SiO-H groups of vacant Tatom sites created by dealumination of BEA zeolite.
The objective of the present work is to extend the method proposed earlier for vanadium and
cobalt and the solid-liquid interface [2-4] to titanium and the solid-gas interface, with TiCl4 vapor
as the precursor. The use of TiCl4 vapor has the advantage to obtain a single isolated
tetrahedral Ti(IV) in framework sites. The series of TixSiBEA zeolites were prepared,
characterized by different spectroscopic techniques and their catalytic and photocatalytic
properties investigated in selective oxidation of propene and photocatalytic decomposition of
N2O in the presence of CO.
The samples prepared by two-step postsynthesis method, hereafter referred to as TixSiBEA (x =
0.3, 0.8, 1.5, 3.2, 5.8 and 9.0 Ti wt %) are white. The incorporation of Ti at tetrahedral Ti(IV)
29
framework sites is evidenced by XRD and the consumption of SiO-H groups by FTIR, Si MAS
1
29
1
NMR, H – Si CP MAS NMR and H MAS NMR.
The progressive increase of the d302 spacing with Ti content is taken as evidence for the
incorporation of Ti into the framework because the Ti-O bond distance (1.79 Å, for
tetracoordinated Ti) is longer than that of Si-O (typically 1.60-1.65 Å in zeolites). After
-1
incorporation of Ti ions in SiBEA, the intensity of a broad IR band at 3520 cm due to H-bonded
29
SiO-H groups and a peak at ~ -101 ppm in Si MAS NMR spectra are significantly reduced,
confirming the reaction between TiCl4 vapor and silanol groups. The lowest intensity of this peak
is observed for Ti9.0SiBEA with the highest Ti content..
The DR UV-vis spectra of TixSiBEA exhibit two main bands at around 220-230 and 265-290 nm
assigned to oxygen-tetrahedral and oxygen-octahedral Ti(IV) ligand to metal charge transfer
(LMCT) transitions respectively, as reported earlier for TiMCM-41 [5]. XPS and XAS
investigations confirm that for low Ti content mainly framework tetrahedral Ti(IV) are present in
TixSiBEA zeolites. The octahedral Ti(IV) framework and/or extra-framework are also formed
whose relative amount increases with Ti content, originating from the high titanium content.
Our catalytic and photocatalytic investigation show that the single tetrahedral Ti(IV) sites are
more efficient than octahedral one.
References
[1] M. Anpo, M. Che Adv. Catal. 44 (1999) 119.
[2] M. Anpo, S. Dzwigaj, M. Che Adv. Catal. 52 (2009) 1.
[3] R. Hajjar, Y. Millot, P.P. Man, M. Che, S. Dzwigaj, J. Phys. Chem. C 112 (2008) 20167.
[4] S. Dzwigaj, M. Che, J. Phys. Chem. B 110 (2006) 12490.
[6] L. Marchese, T. Maschmeyer, E. Gianotti, S. Coluccia, J.M. Thomas, J. Phys. Chem. B 101 (1997) 8836.
39
O6
40
O7
Glycerol etherification over alkaline earth metal oxides
a,*
Mònica Calatayud , Agnieszka M. Ruppert
b,c
and Bert M. Weckhuysen
b
a
Laboratoire de Chimie Théorique CNRS UMR 7616
Univ. P. M. Curie, 4 Pl. Jussieu case 137, 75252 Paris, France
*
[email protected]
b
Inorganic Chemistry and Catalysis group, Dpt of Chemistry, Faculty of Science, Utrecht
University, Sorbonnelaan 16, 3584 CA Utrecht, The Netherlands
c
Institute of General and Ecological Chemistry Technical University of Lodz, 90-924 Łódź, ul.
śeromskiego 116, Poland
Glycerol finds application in many fields such as cosmetics, polymer additives or in the
pharmaceutical industry. Recently an increasing effort is put in the development of new
applications of glycerol derivatives, in order to valorize this molecule [1,2,3]. It is easily obtained
from sugars or as a by-product in the biodiesel process, and might become a platform molecule
in the biorefinery schemes in the near future.
One possible route of its transformation is the etherification to di-, tri- or poly-glycerol. This
reaction is catalyzed by both acid- [4] and base-type catalysts [5]. Alkaline earth oxides have
been successfully used as basic catalysts for this reaction [5], with the conversion to products
increasing with increasing catalyst basicity: MgO<CaO<SrO<BaO. In this work periodic DFT
calculations are carried out to model glycerol interaction with MO (M=Mg, Ca, Sr, Ba) surfaces
[6]. The role of defects has been investigated for a CaO stepped surface (see Figure). In
particular, the adsorption mode and strength of glycerol interaction with the surfaces have been
calculated. Different geometries have been tested for the interaction of glycerol with those
materials. The results are discussed and compared with the experimental data.
Figure: glycerol in interaction with CaO regular (left) and stepped (right) surfaces.
The main conclusions are:
• glycerol interacts with surface acid-base pairs. The geometry of adsorption depends on
the structural parameters of the surface,
• the strength of the interaction correlates with the material basicity: MgO < CaO < SrO <
BaO,
• the dissociation of glycerol increases in the series: MgO (not dissociated) < CaO
(partially dissociated) < SrO (partially dissociated) < BaO (completely dissociated),
• surface defects play a key role in the adsorption process,
• the results of our theoretical calculations are in very good agreement with our earlier
experimental observations of the glycerol etherification reaction over alkaline earth
oxides [5].
References
[1] Y. Zheng, X. Chen and Y. Shen, Chem. Rev 108 (2008) 5253.
[2] M. Pagliaro, R. Ciriminna, H. Kimura, M. Rossi, C. Della Pina, Angew. Chem. Int. Ed. 46 (2007) 2
[3] F. Jérôme, Y. Pouilloux, J. Barrault, ChemSusChem 1 (2008) 586.
[4] J.M. Clacens, Y. Pouilloux, J. Barrault, Appl. Catal. A : General 227 (2002) 181.
[5] A.M. Ruppert, J. D. Meeldijk, B.W.M. Kuipers, B.H. Erné, B.M. Weckhuysen, Chem. Eur. J. 14 (2008) 2016.
[6] M. Calatayud, A.M. Ruppert, B.M. Weckhuysen, accepted Chem. Eur. J.
41
O7
42
O8
Glycerol oxidation on gold catalysts supported on group five metal oxides –a
comparative study with other metal oxide and carbon based catalysts
*
Izabela Sobczak , Katarzyna Jagodzinska, Maria Ziolek
A. Mickiewicz University, Faculty of Chemistry, Grunwaldzka 6, 60-780 Poznań, Poland
*
[email protected]
Introduction
Nowadays much attention has been devoted to applying green catalytic processes to convert
biorenewable feedstock to commodity chemicals and clean fuels [1,2]. Glycerol is a potentially
important biorefinery feedstock, available as a byproduct in the production of biodiesel by
transesterification of vegetable oils or animal fats. Since new energy resources such as
biodiesel fuel have grown in importance in recent years, new uses for glycerol need to be found.
Recently, a series of novel catalytic conversion processes for glycerol transformation was
reported, showing that glycerol can readily be oxidized, reduced, halogenated, etherified, and
esterified to obtain valuable commodity chemicals.
The focus of this work was on gold catalysts applied for liquid phase glycerol oxidation with
oxygen. The main task was to apply new supports for gold (V2O5, Nb2O5, Ta2O5) and to
investigate the effect of group five metal oxides on the efficiency of the oxidation of glycerol.
Gold catalysts based on carbons and metal oxides from Project AuTEK (Al2O3, TiO2 and ZnO)
were also tested for comparison. Our interest was to study the influence of gold-support
interaction on activity and selectivity in glycerol oxidation. Moreover, the influence of preparation
method and gold dispersion is considered.
Experimental
Commercial oxides (V2O5 – Aldrich, Nb2O5(anh) –Alfa Aesar, Nb2O5(aq) – CBMM-Brasil, Ta2O5
–Aldrich) and carbon supports (CAld – Aldrich and CPOCH- POCH) were modified by gold-sol
method [3] with THPC as reducing agent and HauCl4 as a source of gold (1 wt.% of Au).
Additionally, Nb2O5 oxides were modified by deposition-precipitation (DP) method using urea as
reducing agent [3]. The prepared materials were calcined at 623 K for 4 h. All the materials
were charcterised by the use of standard techniques, XRD, UV-Vis, TEM, XPS, test reactions.
For a comparative study, industrial MINTEK catalysts, Au/Al2O3 (0.8 wt. % of Au), Au/TiO2 and
Au/ZnO (1 wt. % of Au ) were used.
The glycerol oxidation experiments were performed in a 300 ml batch reactor from Parr. The
oxidation reactions were carried out with oxygen under pressure 6 atm, at 333 K for 5 h. NaOH
(NaOH/glycerol molar ratio = 2) and 0.2 g of gold catalyst (glycerol/Au molar = 980) were added
to a 1 M aqueous solution of glycerol. The quantitative analyses of the reaction mixtures were
performed by high performance liquid chromatography (HPLC).
The state of Au in the prepared catalysts was studied by XRD, TEM, UV-VIS and XPS. The
results clearly indicated that metallic gold crystallites are formed on all materials and their size is
determined by the chemical composition of the support and the method of Au introduction. It
was found that much bigger Au agglomerates are formed on oxides prepared by depositionprecipitation method using urea than in the case when gold-sol method with the use of THPC as
reducing agent is applied. TEM images allowed the estimation of Au crystallites as ~5 and ~125
nm for gold-sol and DP method, respectively. Among supports modified with the use of THPC
the higher dispersion and smaller gold particle size was obtained on niobia and vanadia as well
as on C ALD than Ta2O5 and C POCH. The oxidation of glycerol with oxygen was investigated
using the Au-catalysts at 333 K and the results are given in Table 1. Similarly as it was shown in
the literature [3], the activity of gold catalysts studied in this work is highly dependent on the Au
particle size and dispersion. Au-oxides prepared by the gold-sol method that leads to a higher
gold dispersion show much higher activity than the catalyst prepared by the precipitation
method. It is worthy of notice that the highest activity among oxide supports, comparable with
43
O8
Au/Carbon, was obtained for Au/Nb2O5 anh (gold-sol). It is due to the SMSI between gold and
niobium.
Table 1. Catalytic activity in Glycerol + O2 oxidation reaction, 333 K, 5h
Catalyst
Au/Nb2O5 anh (gold-sol)
Au/Nb2O5 anh (DP)
Au/Nb2O5 aq (gold-sol)
Au/Nb2O5 aq (DP)
Au/V2O5 (gold-sol)
Au/Ta2O5 (gold-sol)
Au/C ALD (gold-sol)
Au/C POCH (gold-sol)
Au/TiO2 (MINTEK)
Au/ZnO (MINTEK)
Au/Al2O3 (MINTEK)
Glycerol
conv.
%
76
11
31
10
21
13
77
17
91
93
53
Selectivity, %
Glyceric
acid
Tartronic
acid
Glycolic
acid
Formic
acid
Oxalic
acid
Others
30
15
55
3
20
6
36
50
38
31
38
3
4
2
1
30
3
9
1
7
10
8
4
6
1
5
1
3
7
13
4
8
6
3
4
1
4
3
4
11
3
6
4
3
1
2
3
2
60
71
41
82
42
85
43
25
46
42
42
For all the catalysts presented in Table 1 (except Au/V2O5) the highest selectivity to glyceric
acid was observed. The oxidation of glycerol to glyceric acid most probably proceeds via initial
formation of glyceraldehyde, which is rapidly oxidised to glyceric acid. Moreover, tartronic acid
and C2 or C1 by-products were formed. It indicates that after oxidative dehydrogenation (ODH)
of glycerol towards aldehyde and next glyceric and tartronic acids, dehydrogenation and
decarbonation of tartronic acid to glycolic one also occur. The relative rates of each steps of the
reaction are determined by the nature of gold supports and therefore, depending on the support
various selectivity is reached.
Conclusions
• Gold-sol method using for the modification of oxides gives rise to a high gold dispersion
and smaller Au crystallities than deposition-precipitation one. That is why the
modification with Au using THPC as reducing agent is recommended.There is a simple
relationship between the dispersion of gold and the catalytic activity of gold catalysts in
glycerol oxidation.All gold catalysts activate ODH of glycerol towards glyceric and
tartronic acids. The next step, dehydrogenation and decarbonation of tartronic acid to
glycolic one also occurs and depends on the nature of the support.Among group five
metal oxide supports the best activity is reached if gold is supported on Nb2O5 (anh),
but it is slightly lower than that of MINTEK gold catalysts based on titania and ZnO.
Acknowledgements
Polish Ministry of Science and Higher Education (grant 118/COS/2007/03) and COST
D36/0006/06 are to be acknowledged for a partial support of this work. We also thank Project
AuTEK as source of some of the catalysts (Au/Al2O3, Au/ZnO, Au/TiO2) and Johnson Matthey
(UK-USA) for supplying HauCl4.
References
[1] Y. Zheng, X. Chen, Y. Shen, Chem. Rev. 108 (2008) 5253–5277.
[2] Ch.-H. Zhou, J. N. Beltramini, Y-X. Fan, G. Q. Lu, Chem. Soc. Rev. 37 (2008) 527 – 549.
[3] S. Demirel-Gulen, M. Lucas, P. Claus, Catal. Today 102–103 (2005) 166–172.
44
O9
Etherification of Glycerol and Other Biomass-Derived Polyols: New Routes to Valuable
Bulk Chemicals
a
a
a,b
a
Andrei N. Parvulescu *, Pieter C. A. Bruijnincx , Peter J.C. Hausoul , Maria Arias ,
b
a
Robertus J.M. Klein Gebbink and Bert M. Weckhuysen
a
Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Faculty of
Science, Utrecht University, Utrecht, The Netherlands;
b
Chemical Biology & Organic Chemistry, Debye Institute for Nanomaterials Science, Faculty of
Science, Utrecht University, Utrecht, The Netherlands;
[email protected]
Objectives
New catalytic routes have to be developed to transform renewable highly oxygenated platform
molecules to valuable bulk and fine chemicals [1]. The polyols constitute an important class of
these biomass-derived oxygenates, with glycerol being a prime example. Glycerol is produced
in large quantities as a by-product of biodiesel production, i.e. for every 1000 kg of fatty acid
esters around 100 kg of glycerol is formed. Although glycerol itself has a lot of commercial
applications, e.g. in the cosmetic and pharmaceutical industries, new attractive applications
should be introduced to improve the economics of the biodiesel process [2]. Furthermore,
glycerol is regarded as a potential platform molecule since it can be directly produced from
sugars or sugar alcohols, which are considered as the cornerstones of future biorefinery
schemes. The development of new catalytic routes for glycerol valorization is therefore of great
importance. In this respect, etherification of glycerol [3] or, indeed, other biomass-derived
polyols represents an important application as the products can be used as fuel additives,
intermediates in the pharmaceutical industry, agrochemicals or as non-ionic surfactants. In this
contribution we will discuss the recent efforts of our group which have focused on
glycerol/polyol valorization [4] through etherification with long linear alkenes.
Results
In our approach, we investigated the direct etherification of glycerol with a long linear alkene
using as a model 1-octene over solid acid catalysts [3]. Remarkably, the catalytic etherification
route of direct nucleophilic addition of glycerol to linear, long-chain olefins has been little
explored even if this process may provide a direct route to long alkyl chain ethers with potential
surfactant application. Therefore we decided to screen various heterogeneous acid catalysts in
the etherification of neat glycerol with 1-octene. Zeolites showed modest conversions compared
to Amberlyst 70 or pTSA, but superior selectivities towards the most valuable monoether
products. The highest activity was obtained with H-Beta zeolites, which gave excellent
selectivities for the mono and di-octyl ethers of glycerol of always > 85 %. H-Beta with a Si/Al
ratio of 12.5 gave the highest conversion (15 %) and the highest selectivity to the mono-octyl
ether (94 %). Several factors were found to influence both the etherification activity and the
selectivity. Hydrophilic properties and porous structure of the catalyst turned out to be the
critical parameters. Other parameters like reaction time, 1-octene: glycerol molar ratio, reaction
temperature and the addition of an inert gas were investigated in order to improve the
etherification activity of H-Beta zeolite. Catalysts deactivation due coke formation was
investigated as well. In addition, the catalyst was recovered and re-used in 3 reaction cycles
without any loss of activity or selectivity (Table 1). The substrate scope was successfully
extended to other bio-based polyols and the results will be also discussed.
Table 1. Re-use of H-Beta (37.5) zeolite in the etherification of glycerol with 1-octene.
Run
1
2
3
Conv.(%)
14
13
14
Sel.C8Glyc (%)
78
80
79
Sel.C16Glyc (%)
14
13
12
Sel.other(%)
8
7
9
Reaction conditions: 1 g of catalyst, 1-octene: glycerol 3:1, 5 h, 10 bar Ar, 140 °C.
45
O9
OH
HO
OH
OH
HO
EG
1,2-PD
HO
OH
HO
HO
1,3-PD
Glycerol
Figure 1. Etherification of alcohols with 1-octene over H-Beta (Si/Al =12.5).
Conclusions
The direct etherification of glycerol and glycols with 1-octene in a solvent-less system is
possible by using heterogeneous acid catalysts. The type of the solid acid used strongly
influences the activity and selectivity of the etherification process. H-Beta zeolites proved to be
the most selective etherification catalysts, whereas for Amberlyst-70 a high amount of byproducts were formed. H-Beta (12.5) produced the C8Glyc and C16Glyc ethers with 96 %
selectivity at 16 % conversion. H-Beta zeolites were succesfully applied in etherification of other
bio-based polyols. These results show the potential of using heterogeneous acid catalysts for
the green synthesis of valuable long alkyl mono- or di-ethers of various bio-based alcohols.
Acknowledgements
We would like to thank the ASPECT-ACTS Program for financial support.
References
[1] Gallezot, P., ChemSusChem, 2008, 1, 734-737.
[2] Jérome, F., Pouilloux, Y., Barrault, J., 2008. Rational design of solid catalysts for the selective use of glycerol as a
natural organic building block, ChemSusChem, 2008, 1, 586-613.
[3] Ruppert, A. M.; Meeldijk, J. D.; Kuipers, B. W. M.; Erne, B. H.; Weckhuysen, B. M. Chem. Eur. J. 2008, 14, 20162024
[4] Ruppert, A. M.; Parvulescu A. N.; Arias, M.; Hausoul P. C.; Bruijnincx P. C. A.; Klein Gebbink, R. J. M.; Weckhuysen,
B. M. J. Catal. 2009, submitted for publication
46
O10
Relevance of the physicochemical properties of CaO catalyst for the methanolysis of
triglycerides to obtain biodiesel
a
a
a*
a
a
D. Martín Alonso , F. Vila , R. Mariscal , M. Ojeda , M. López Granados , J. Santamaríab
González
a
Instituto de Catálisis y Petroleoquímica, CSIC, C/Marie Curie 2, Campus de Cantoblanco, Eb
28049, Madrid, Spain. Departamento de Química Inorgánica, Cristalografía y Mineralogía
(Unidad Asociada al ICP-CSIC), Facultad de Ciencias, Universidad de Málaga, Campus de
Teatinos, 29071 Málaga, Spain.
*
[email protected]
Objective
Calcium oxide is a suitable solid catalyst for the production of biodiesel (fatty acid methyl esters,
FAME) via triglycerides methanolysis reaction [1]. The physicochemical properties of metallic
oxides may be affected significantly by the preparation method [2]. Therefore, we have
investigated a series of different CaO precursors with the final aim of improving the biodiesel
yield. A detailed characterization study of all materials has been also carried out to establish a
structure-activity relationship.
Results
Four calcium oxide samples were prepared by thermal decomposition of different calcium salts
commercially available: carbonate (CaO-C), acetate (CaO-A), oxalate (CaO-O) and nitrate
(CaO-N). Two additional samples were prepared by decomposition of Ca(OH)2 previously
prepared by controlled addition of a NaOH solution to aqueous solutions of calcium acetate
(CaO/OH-A) and nitrate (CaO/OH-N). The precursor decomposition process was characterized
by EGA-MS spectrometry, which allows the determination of the minimum temperature required
to obtain CaO. Accordingly, all samples were first decomposed ex-situ at 1073 K during 1 h
under an O2/Ar flow (20/80 v/v). Subsequently, the samples were cooled down in N2 flow and
loaded in a batch reactor avoiding any contact with ambient air to thus prevent sample hydration
and carbonation.
100
FAME yield (%)
80
60
CaO-C
CaO-A
CaO-O
CaO-N
CaO/OH-A
CaO/OH-N
40
20
0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Time (h)
Figure 1. FAME yield obtained with the different CaO samples.
47
O10
Figure 1 shows that there is one group of active catalysts (CaO-C, CaO-A, CaO-O and
CaO/OH-A), with minor differences among them, that reach a 90 % yield to FAME in 3 h (> 80
% in 2 h). In contrast, CaO-N and CaO/OH-N depict low FAME yields (<30 % in 3 h) at the
same conditions.
To understand the observed catalytic performance, we have characterized the activated CaO
samples by XRD and N2 adsorption-desorption isotherms. XRD patterns for all activated
samples are almost identical, presenting exclusively diffraction lines assigned to the CaO phase
(JCPDS 77-2376). The average crystal size (Table 1) has been determined by using the DebyeScherrer equation to the diffraction peak at 2θ=37.4º. The smallest CaO crystallites are
obtained when calcium acetate and oxalate are used, while calcium nitrate precursors lead to
the larger particles. Table 1 also summarizes the textural properties (BET surface area, pore
volume and pore diameter) for all samples. The most active samples (CaO-C, CaO-A, CaO-O
2 -1
and CaO/OH-A) show similar BET surface areas (20-27 m .g ) and higher than the almost
inactive samples (CaO/OH-N and CaO-N).
Table 1. Crystal size (XRD), textural properties (N2 isot.) and basicity (FTIR-pyrrole) of CaO samples
Sample
Crystal
size
(nm)
BET
surface
area
2 1
(m ·g )
Pore
volume
3 -1
(cm ·g )
Pore
diameter
(nm)
Intensity (a.u.) at
-1
RT of 1446 cm
band
CaO-C
67
25.9
0.27
41
1.20
CaO-A
37
21.9
0.18
33
0.46
CaO-O
47
25.7
0.24
38
0.40
CaO-N
116
<1.0
--
--
--
CaO/OHA
60
26.7
0.16
24
--
CaO/OHN
93
6.8
0.05
33
--
The basicity of the catalysts was evaluated by FT-IR of adsorbed pyrrole (C4H4NH) as a probe
molecule. Pyrrole is an amphoteric substance that interacts with the surface basic sites at the
sample by forming a H-bond between the NH group and the framework oxygen atoms (C4H4NHO). Therefore, it has been often used to detect and estimate the strength of base sites on oxide
surfaces [3]. The most active samples (CaO-C, CaO-A, CaO-O) show a clear band centered at
-1
1446 cm associated to pyrrolate species formed on strong base sites on the solid (Table 1).
Furthermore, we have noted that the intensity and thermal stability of this band (indicative of the
number and strength of basic surface sites, respectively) can explain the small differences
observed among the most active catalysts. Interestingly, when calcium nitrate takes part in any
step of the preparation of calcium oxide, low surface areas are obtained, and consequently, the
observed catalytic performance is poor. In summary, an excellent CaO catalyst for methanolysis
of triglycerides to obtain biodiesel should not involved the use of calcium nitrate salt as a
precursor. Moreover, the suitable preparation method should yield small CaO particles
displaying elevated surface area and a high number of strong basic sites on the surface.
Conclusions
In all cases, our data strongly suggest that crystal size, textural properties and base character
are key parameters in the catalytic behaviour of CaO materials in the triglycerides methanolysis
reaction to produce biodiesel. These physicochemical properties are determined by the calcium
salt used as precursor of the CaO.
References
[1] M. Lopez Granados, M.D. Zafra Poves, D. Martin Alonso, R. Mariscal, F. Cabello-Galisteo, R. Moreno-Tost; J.
Santamaría, J.L.G. Fierro, Appl. Catal. B: Environ. 73 (2007) 317-326.
[2] T. Matsuda, J. Tanabe, N. Hayashi, Y. Sasaki, H. Miura, K. Sugiyama, Bull. Chem. Soc. Jpn. 55 (1982) 990-994.
[3] D. Murphy, P. Massiani, R. Frank, D. Barthomeuf; J. Phys. Chem. 100 (1996) 6731-6738.
48
O11
Influence of porosity and surface groups on catalytic activity of carbon materials for the
microwave-assisted CO2 reforming of CH4
B. Fidalgo, A. Arenillas, J.A. Menéndez
*
Instituto Nacional del Carbón, CSIC, Apartado 73, 33080 Oviedo, Spain
[email protected]
Objective
The use of carbon materials as catalysts for hydrocarbon pyrolysis reactions has been
extensively studied, since carbon-based catalysts offer some advantages over metal catalysts
as availability, durability and low cost. Besides, they are usually good microwave receptors,
which is advantageous in case of heating by using microwaves.
It has been observed that the decomposition of CH4 using carbon catalysts occurs mainly in
micropores, and a rapid deactivation is observed after high initial conversions as a
consequence of blockage of pores by carbonaceous deposits. Microwave-assisted dry
reforming of CH4 (reaction 1) has been proposed as a viable “in situ” regeneration process,
thanks to the gasification of the generated deposits with CO2. Besides, high conversions can be
achieved since microwave heating enhances heterogeneous reactions and heterogeneous
catalytic reactions (as CO2 gasification and CH4 decomposition, respectively).
Dry reforming reaction: CH4 + CO2 ↔ 2H2 + 2CO
∆H298K = +247 kJ/mol (1)
On the other hand, a clear connection between catalytic activity of carbons and surface groups
has not been established since contradictory results about the role of surface chemistry and
CH4 decomposition can be found.
The aim of the present work is to investigate factors governing catalytic activity of carbonaceous
materials in the microwave-assisted CO2 reforming of CH4 reaction, focusing on textural and
surface properties.
Results
Conversion (%)
In order to study the influence of porosity, carbon materials with different textural properties
were tested as catalysts for the microwave-assisted dry reforming reaction (metallurgical coke,
activated carbon and carbon xerogel). Experiments were conducted in a quartz reactor charged
with the carbon used as catalyst/microwave receptor (C/MR) and heated in a single mode
microwave oven.
100
100
80
80
CO2 conversion
60
CH4 conversion
60
40
40
20
FY5
CQ
20
0
FY5
CQ
0
0
25
50
75
100
125
150
0
Time (min)
25
50
75
100
125
150
Time (min)
Figure 1. Conversions for microwave-assisted dry reforming carried out over a commercial activated carbon (FY5) and
a metallurgical coke (CQ). Operating conditions: microwave oven; T = 800 ºC; 50%CH4 – 50%CO2; VHSVtotal-FY5 = 0.32
L/g h and VHSVtotal-CQ = 0.64 L/g h.
It was found that large microporosity is necessary for an acceptable catalytic activity of carbons.
Thus, carbonaceous materials without development of microporosity gave rise to negligible
conversions (case of metallurgical coke, CQ in Figure 1), whereas high conversions were
attained using carbons with large micropores volumes as catalysts (case of the activated carbon
FY5 in Figure 1). Besides, to keep high CH4 and CO2 conversions with time, the microporosity
49
O11
must be preserved from being blocked, which depends on the operating conditions used, mainly
the proportion of CO2.
Presence of mesopores in the catalyst was also studied by testing carbon materials with
controlled porosity (carbons with similar micropores volumes but different mesopores volumes).
However, it was not observed so clear influence on the catalytic activity as in the case of
microporosity.
In order to investigate the effect on dry reforming of the presence of oxygen groups on the
surface of carbon catalysts, commercial activated carbons were modified by oxidation (using a
saturated solution of (NH4)2S2O8, added in a proportion of 1g of activated carbon per 10 mL of
solution). Obviously, oxidized activated carbons shows higher volatile matter and oxygen
content, but no important change in textural parameters regarding original carbons is observed.
Oxygen surface groups reduced dramatically the catalytic activity of activated carbons, giving
rise to much lower conversions than original carbons (compare FY5 in Figure 1 with conversion
profiles in Figure 2). From the point of view of individual reactions, CO2 gasification seems to be
more negatively affected. Actually, CO2 conversion was lower than CH4 conversion at any time,
which had not been observed with non-oxidized activated carbons before.
100
Conversion (%)
100
CO2 conversion
80
60
CH4 conversion
80
60
MW
40
EF
MW
EF
40
20
20
0
0
0
25
50
75
Time (min)
100
125
150
0
25
50
75
100
125
150
Time (min)
Figure 2. Conversions for dry reforming carried out over oxidized activated carbon and under conventional (EF) or
microwave (MW) heating. Operating conditions: FY5ox; T = 800 ºC; 50%CH4 – 50%CO2; VHSVtotal = 0.32 L/g h.
Interestingly, performance of microwave-assisted dry reforming over oxidized carbons was
worse than under conventional heating, contrary to the results expected, since microwave
heating is known to give rise to enhanced conversions when dry reforming is carried out over
original carbon materials. This could be due to trouble to heat oxidized activated carbons in the
microwave device, caused by less density of delocalized π-electrons, making more difficult the
generation of microplasmas.
Conclusions
Catalytic activity of carbon materials for dry reforming is mostly determined by their textural and
surface properties.
Dry reforming of CH4 over carbon materials occurs mainly in micropores. Therefore, large
micropores volumes are related with high conversions and blockage of microporosity with a
reduction in the catalytic activity.
Addition of oxygen surface groups diminishes significantly the catalytic activity of activated
carbons respect to original carbons. Microwave-assisted dry reforming is specially affected
(more than conventionally heated) since oxidized activated carbons are more difficult to be
heated in the microwave oven.
50
O12
Niobium Oxide Species in and on Silica Materials; a Molecular Picture
*
Frederik Tielens and Stanislaw Dzwigaj
UPMC Univ Paris 6, UMR 7609, Laboratoire de Réactivité de Surface, 4 Place Jussieu, 75252
Paris Cedex 05, France
CNRS, UMR 7609, Laboratoire de Réactivité de Surface, 4 Place Jussieu, 75252 Paris Cedex
05, France
[email protected]
Introduction
Recently [1,2], we have described the Si lattice substitution by V in a sodalite (SOD) structure
using ab initio periodic DFT calculations. Different vanadium framework sites models have been
proposed after a systematic theoretical study of the substitution of a T-site by vanadium atoms.
The vanadium framework sites were characterized by their calculated geometrical parameters,
and vibrational frequencies. The results obtained were fully consistent with experimental data
reported earlier by Dzwigaj et al. [3,4] and allowed to identify the molecular structure of the
vanadium sites in the zeolite framework. Beside de substitution of Si atoms in zeolites by
transition metals other silica based materials have been used, such as meso porous materials
MCM-41 and SBA-15. For the preparation of such materials both, co-precipitation and postsynthesis methods were applied.[5,6] The grafting of V-oxide on an amorphous silica surface
has been modelled [7] and described in parallel with experimental data. In the present work we
characterize the Nb substituted and grafted sites in the zeolite framework and on an amorphous
silica surface. The results are related and discussed with experimental data obtained by
spectroscopic techniques.
Si
O
OH
O
T
Si
O
O
O
Si
O
O
Si
Figure 1. Most stable configuration for
Nb incorporated in a zeolite framework
Figure 2. Phase diagram (surface energy vs.
temperature) showing the stability ranges for
the different grafting geometries.
Different possible molecular models for active sites in niobium substituted silicate zeolites were
investigated. It was found that the isomorphous substitution of niobium into the zeolite structure
is slightly endothermic and the formation of Nb(III) site containing bridging hydroxyls is very
seldom or even not present in the sodalite structure. The most favorable Nb(V) structure is one
having a Nb(V)O-H group and Nb linked by four V-Osi bounds to the zeolitic walls (T5 site). The
Nb(V)=O site is less stable than the T5 site, but when hydrated becomes similar in stability as
the hydrated T5 site. The Niobium zeolites are hydrophilic but the active site’s geometry is less
influenced by the presence of water located in the center of the sodalite cage.
Concerning the grafted species one obtained from a first principle thermodynamic approach that
the most stable species at low temperature is the mono-grafted Onb(OH)2(O-Si) complex. This
configuration corresponds to the fully hydrated niobia catalyst on the silica support. An increase
in temperature or a decrease in hydration stabilizes the di-grafted Onb(OH)(O-Si)2 complex as
observed. High temperatures iusep the formation of the pyramidal Onb(O-Si)3 arrangement.
51
O12
Conclusions
Niobium containing zeolite BEA was successfully synthesized. The characterization of this
material indicated that niobium is incorporated into the zeolite framework. First principle
calculation techniques were performed to investigate the nature of the Nb site in the zeolite
framework. It was found that the Nb site is a Nb(V) having a Nb(V)O-H group and Nb linked by
four Nb-Osi bounds to the zeolitic walls. The grafting geometry is depending on the degree of
hydration, however the Onb(OH)(O-Si)2 complex is found to have the largest domain of stability
as a function of the temperature.
In general it is found that substitution or grafting of Nb oxide species do not have the same
molecular structure.
Acknowledgements
The authors thank GENCI project x20090812022 and the CINES, IDRIS and CCRE (Université
Pierre et Marie Curie) for providing the computation facilities. Polish Ministry of Science and
Higher Education (grant 118/COS/2007/03) and COST D36/0006/06 are to be acknowledged
for a partial support of this work.
References
[1] F. Tielens, M. Trejda, M. Ziolek, S. Dzwigaj, Catal. Today 139 (2008) 221.
[2] F. Tielens, M. Calatayud, S. Dzwigaj, M. Che. Micropour. Mesopour. Mater. 119 (2009) 137.
[3] S. Dzwigaj, E.M. Ei Malki, M.J. Peltre, P. Massiani, A. Davidson, M. Che, Topics Catal. 11/12 (2000) 379.
[4] R. Hajjar, Y. Millot, P.P. Man, M. Che, S. Dzwigaj, J. Phys. Chem. C 112 (2008) 20167.
[5] X. Gao, I.E. Wachs, M.S. Wong, J. Y. Ying, J. Catal., 203 (2001) 18-24.
[6] M. Ziolek, I. Nowak, Zeolites, 18 (1997) 356-360.
[7] M.M. Islam, D. Costa, M. Calatayud, F. Tielens, J. Phys. Chem. C, 113, 10740 (2009).
52
O13
Study of Nanoporous Catalysts in the Selective Catalytic Reduction of NOx
María José Orellana Rico, Ramón Moreno Tost, Antonio Jiménez López, Enrique
*
Rodríguez Castellón
Departamento de Química Inorgánica, Cristalografía y Mineralogía (Unidad Asociada
al ICP-CSIC), Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos, 29071
Málaga (Spain)
[email protected]
Objective
The SCR of NO with ammonia is an effective, selective and available industrial process to
control the emissions of NO from stationary sources. On the other hand, its application remains
limited to the control of NOx emissions from stationary sources and mobile sources such as
trucks, diesel locomotives or maritime transport, but it is not viable for light vehicles. In addition,
the current catalyst based on V2O5-WO3(MO3)-TiO2 suffers processes of deactivation for sulfur
and heavy metals compounds [1] and, moreover, the issues related to vanadium toxicity. The
discovery of catalysts based on zeolite active in the SCR process using hydrocarbons as
reducing agents, has focused the interest of the researchers on non-zeolite materials. Thus,
siliceous SBA-15 materials have been proposed as supports for the SCR of NO with
hydrocarbons [2], in which high dispersion of the active metal and good performance have been
attained.
The main goal of this work is the study of a mesoporous silica with SBA-15 (Si) structure
prepared by means of a low cost synthetic route [3] as support of copper catalysts (ca. 1-6wt%).
It has been also synthesized an alumina grafted on the mesoporous silica (SiAl) with a Si/Al
molar ratio of 10. Copper catalysts have been characterized and tested in the SCR of NO with
propane in excess of oxygen.
Results
The textural parameters of Si and SiAl supports show that the aluminum is incorporated mainly
inside of the pores of the mesoporous silica since a reduction in the mean pore diameter and
pore volume took place as well as an increase of the width of the pore walls. Moreover, the
XRD patterns of the Si and SiAl supports show that the hexagonal structure of SBA-15 is
maintained after grafting with alumina.
The copper was incorporated into the Si and SiAl supports by means of incipient wetness
method. The XRD patterns of copper catalysts show that for a same copper loading, the
presence of aluminum improves the active phase dispersion over the support. On the other
hand, XPS analysis of catalysts points out that copper is present as CuO and a spinel-like
structure in the SiAl_3 and SiAl_6 catalysts as well. The copper dispersion over the supports
has been studied by means of N2O decomposition showing that the aluminum exerts a
favorable effect on the copper dispersion and therefore, over the metal surface exposed.
These catalysts have been tested in the SCR of NO with propane in the presence of oxygen.
Figure 1 depicts the catalytic activity of Si_x and SiAl_x respectively. Si_1 catalyst shows the
highest conversion of NO among the Si_x catalysts. This fact is due to the highest dispersion of
copper since the particle size (1.9 nm) is lower than those observed for Si_3 and Si_6, 8.8 and
10.9 nm, respectively. In addition, these particles are more reducible than the larger ones of
Si_3 and Si_6, respectively. On the other hand, SiAl_3 catalyst displays the higher conversion
of NO for the catalysts tested.
53
O13
25
20
NO Conversion (%)
NO Conversion (%)
20
15
10
5
15
10
5
0
250
350
450
0
250
550
Tem perature (ºC)
350
450
550
Tem perature (ºC)
Si_6
Si_3
Si_1
SiAl_6
SiAl_3
SiAl_1
Figure 1. Catalytic performance of Si_x and SiAl_x. Catalytic conditions:1000ppm NO, 1000ppm C3H8, 2.5vol%O2,
balance He and total flow = 75 mL/min.
In this case, the copper loading increase over SiAl supports does not involve an increase of the
particle size (1.0 and 1.8 nm for SiAl_1 and SiAl_3, respectively). However, the loading increase
from 3wt% to 6wt% (6.8 nm) is high enough to produce larger copper particles, which do not
produce an improvement in the catalytic activity. Furthermore, it has been studied the effect of
NO, C3H8, O2 and space velocity in the catalytic performance of SiAl_6 catalyst 450ºC with. As it
was expected, the parameter whose influence was greater in the catalytic activity was the space
velocity since the NO conversion reached 90% when the flow was reduced up to 50mL/min,
however if the total flow was increased up to 150 mL/min the NO conversion was 15%.
SiAl_3 catalyst has been tested in presence of H2O and SO2 in the feed. The Figure 2 shows
the catalytic results showing that the presence of SO2 improves the NO conversion while the
presence of H2O exerts a negative effect on the catalytic performance.
The beneficial effect of SO2 has been already
reported by the authors [4] in the case of mordenite
zeolites exchanged with copper. This effect was
attributed to the presence of superficial CuSO4
active in the SCR reaction.
40
NO Conversion (%)
35
30
25
20
15
10
5
0
250
350
450
550
Tem pe rature (ºC)
std
H2O
SO2
SO2+H20
Figure 2. Effect of SO2 and H2O in the SCR of NO with propane
Acknowledgements
The authors are grateful to financial support from CICYT (project NAN20004-09267-C01) and
Junta deAndalucía (PO6-FQM-01661).RMTwould like to thanks the Ministry of Science and
Innovation (Spain) for the financial support under the Program Ramón y Cajal (RYC-200803387).
References
[1] G. Busca, M. A. Larrubia, L. iusep, G. Ramis, Catal Today 107-108 (2005) 139
[2] N. El Hassan, A. Davidson, Patrick Da Costa, G. Djéga-Mariadassou, Catal Today 137 (2008) 191.
[3] M. Gómez Cazalilla, J.M. Mérida Robles, A. Gurbani, E. Rodríguez Castellón, A. Jiménez López, J. Solid State
Chem. 180 (2007) 1130.
[4] R. Moreno-Tost, J Santamaría-González, E. Rodríguez-Castellón, A. Jiménez-López., M. A. Autié, E. González, M.
Carreras Glacial, C. De las Pozas, Appl. Catal. B 50 (2004) 279
54
O14
New HDS catalysts supported on thiol functionalized mesoporous silica
a
b
a
Valeria La Parola , Brindusa Dragoi , Anna Maria Venezia *
a
Istituto per lo Studio dei Materiali Nanostrutturati (ISMN-CNR) via Ugo La Malfa, 153, Palermo,
b
I-90146; Technical University, Faculty of Chemical Engineering,Laboratory of Catalysis, 71A D.
Mangeron Ave. 700050 – Iasi, Romania
[email protected]
A great part of the research for hydrotreament is nowadays looking at new materials as
catalysts support, among these, ordered mesoporous silicas (MCM-41, HMS, SBA-15) have
recently attracted much interest due to their high surface area and controlled porosity [1-2]. With
respect to the CoMo or NiMo type of HDS catalysts, an important role is played by the active
species particle sizes. In the present study, aiming to increase the dispersion and consequently
the activity of the supported active phase, siliceous HMS and SBA-15 were functionalised with
mercaptosilanes by direct synthesis [3-4]. The silica oxides were then functionalized with –
C3H6SH groups by co-condensation of tetrahetylorthosilicate (TEOS) and 3
mercaptopropyltriethoxisilane (3-MPTS) in the presence of the appropriate surfactant, either
dodecylammine for the synthesis of HMS and Pluronic P123 for the SBA-15. The functionalised
silica were then used as supports for CoMo catalysts. The CoMo catalysts were obtained by
co-impregnation of aqueous solution of (NH4)6Mo7O24·4H2O (Mo= 7wt%) and Co(NO3)2 6H2O
(Co=1.7wt%), followed by 2 h drying at 120°C and 4 h calcinations at 400°C. The materials
were characterized by N2 physisorption, XRD (SAXS and WAXS), TEM and XPS. Their catalytic
activity was tested in the HDS of thiophene. An effect of the support morphology was observed
with the HMS giving rise to more active catalysts. According to TEM and XPS analyses, the
functionalization of the support did not increase the metal dispersion. However, the thiol
modified supports contributed to an increased activity of the supported CoMo catalysts.
According to the XPS results the main effect of the thiol group consisted in a decrease of the
Mo(VI) and Co(II) reducibility and less sulphides formation.
References
[1] A. Corma, A. Martinez, V. Martinez-Soria, J. Catal. 169 (1997), 480.
[2] T. A. Zepeda, B. Pawelec, J. L. G. Fierro, A. Olivas, S. Fuentes, T. Halachev, Micropor. Mesop. Mater. 111 (2008)
157.
[3] N. Marin-Astorga, G. Pecchi, T. J. Pinnavaia, G. Alvez-Manoli, P. Reyes, J. Mol. Catal. A 247 (2006) 145.
[4] D. Zhao, J. ius, Q. Huo, N. Melosh, G.H. Fredrickson, B.F. Chmelka, G.D. Stucky, Science 279 (1998) 548-552.
55
O14
56
O15
Structural flexibility in ~SbVO4
*,a
b
Angel R. Landa Cánovas , F: Javier García-García and Staffan Hansen
c
a
Instituto de Ciencia de Materiales de Madrid, CSIC, E-28049, Madrid, Spain.
Lehrstuhl für Festkörperchemie, Institut für Physik, UniVersität Augsburg, UniVersitätsstrasse
1, D-86159 Augsburg (Germany).
c
Division of Polymer and Materials Chemistry, Department of Chemistry, Lund University,
Chemical Center, P.O. Box 124, SE-221 00 Lund, Sweden
b
Objective
~SbVO4 is a well known catalyst used for the ammoxidation of propane to acrylonitrile.
Vanadium site isolation as well as cooperation with Sb2O4 is considered to be very important
for the catalysis. However, very little importance is given to the structural flexibility exhibited by
~SbVO4 phase. The purpose of this communication is to highlight the high structural flexibility
exhibited by this phase accommodating the changes in the oxidation state of vanadium which is
accompanied by the introduction of cation vacancies.
Results
~SbVO4 presents rutile-type structure with antimony in 5+ oxidation state while vanadium
ranges from 3+ to 4+ depending on the reaction conditions. ~SbVO4 exhibits a wide range of
3+
4+
non-stoichiometry [1] since substitution of V by V requires the introduction of cation
5+
vacancies, see reaction 1 in Figure 1. Besides, Sb can substitute vanadium according
reaction 2 or according reaction 3 in Figure 1. The whole existence interval of ~SbVO4 is given
5+
4+
3+
by the general expression Sb 8/9 –yV 2/9+3x+2yV 8/9-4x-y xO4 where 0 ≤ x ≤ 2/9 and 0 ≤ y ≤ 8/94x. In this way, up to almost 1/8 of the total cation positions can be vacant. However, ~SbVO4
rutile phase can accommodate such a big amount of cation vacancies in a very soft way,
through vacancy population waves which give rise to incommensurate structural modulations,
without the collapse of the structure as it usually happens in other rutile phases through
crystallographic shear defects. In Figure 2 we show a high resolution TEM micrograph showing
bright white dots due to the rutile cation positions, with their intensity scanned in the upper right
graph, and wider dark bands generated by the soft accommodation of cation vacancies in the
rutile structure with their intensity scanned in the lower right graph.
Figure 1.- Diagram showing the existence margins for the rutile-type SbVO4.
57
O15
[110]r
Figure 2-a. High resolution TEM image of oxidized SbVO4 phase showing bright white dots which correspond to the
cationic rutile positions and wide dark bands generated by cationic vacancies. Intensity line scan graphics of the lattice
rutile positions (-b) and of the cation vacancy waves (-c).
Reference
[1] A.R. Landa-Cánovas, J. Nilsson, S. Hansen, K. Ståhl and A. Andersson. J. Solid State Chem. 116, 369-377 (1995)
58
O16
Synthesis of Pt nanoparticles on poly(3,4-ethylenedioxythiophene) modified electrodes
for the electrocatalysis of Methanol.
a
a
a
b
a
A. Colina *, M.A. Heras , A.C. Fernandez , V. Ruiz , J. López-Palacios
a Department of Chemistry,University of Burgos, Pza. Misael Banuelos s/n.E- 09001, Burgos
(Spain)
b Nanomaterials Group, Dept. of Engineering Physics, Helsinki University of Technology, PO
Box 5100, FI-02150 Espoo (Finland)
* [email protected]
Objective
Among the different methods of synthesis of nanoparticles (NPs) for catalytic purposes,
chemical synthesis is the most used strategy [1]. Electrochemical synthesis exhibits some
advantages when NPs are going to be used for electrocatalysis [2,3]. The main improvement is
that NPs are strongly attached to the electrode in only one step. The size, shape and number of
deposited nanoparticles depend dramatically on the electrode material. Conducting polymers
(CP) have been used as support for catalysts and are promising materials because CP are
good dispersing material for NPs and introduce a high porosity and roughness, which generate
a large surface area. However, the method used for the CP and NPs synthesis has a deep
influence on the nanocomposite catalytic properties. The main objective of this work is to
electrosynthesize Pt nanoparticles with high catalytic activity for methanol electrooxidation. We
present in this communication the synthesis of poly(3,4-ethylenedioxythiophene) (PEDOT), as
support for Pt NPs (PEDOT/Pt), in aqueous media without using any surfactant.
Results
Electropolymerization of 3,4-ethylenedioxythiophene (EDOT) was performed in absence of
surfactants by applying an anodic potential high enough to oxidize the monomer and form a
polymer film on a glassy carbon electrode. Monomer concentration, time and applied potential
are key parameters to generate a film with good properties for hosting and dispersing catalytic
particles.
Pt Nanoparticles were formed on PEDOT modified electrode using cyclic voltammetry in a
22PtCl6 solution. In this case, PtCl6 concentration, potential, number of cycles and scan rate are
the most important parameters to control and form high catalytic nanostructures.
The synthesis of the nanocomposites has been followed using in-situ spectroelectrochemistry.
Changes in the reflectance of the electrode provide valuable information on the deposition
process.
The catalytic materials were also characterized using in-situ Raman spectroscopy at open
circuit potential. Raman spectra of PEDOT/Pt NPs composites were very similar to that of
PEDOT films [4,5]: the oxyethylene ring deformation, symmetric C-S-C deformation, C-O-C
deformation, Cα-Cα’ stretching and symmetric Cα=Cβ(-O) stretching were observed in the two
materials.
The nanocomposites were used as catalyst for
the oxidation of methanol. When appropriate
synthesis conditions were used, the typical
voltammogram of methanol was obtained. A
forward oxidation peak appears around +0.70 V
vs. Ag/AgCl, and a backward oxidation peak
appears around +0.57 V.
Figure shows a SEM image of one of the
PEDOT/Pt composites generated on the glassy
carbon electrode
59
O16
Conclusions
It is possible to synthesize electrochemically a PEDOT/Pt NPs composite in two consecutive
2steps: potentiostatic polymerization of EDOT and potentiodynamic reduction of PtCl6 on the
PEDOT film. UV-Visible spectroelectrochemistry and Raman spectroscopy using a 785 nm laser
have demonstrated to be very useful techniques to characterize these materials.
2-
The voltammetric reduction of PtCl6
on PEDOT film
homogeneously distributed on the conducting polymer matrix.
generates
Pt
nanoparticles
Raman spectra confirm that PEDOT film is obtained successfully in absence of any kind of
surfactant in aqueous media and it is modified by Pt nanoparticles.
The electrosynthesized composite is a good catalyst for the oxidation of methanol.
Acknowledgements
Support from University of Burgos, Caja de Burgos, Ministerio de Ciencia e Innovación
(MAT2006-13875), Junta de Castilla y León (GR71, BU006A09, BU012A09), COST Action D36
(WG D36-0005-06), Academy of Finland (V.R., Academy Research Fellowship) is
acknowledged.
References
[1] Drillet, J. F.; Dittmeyer, R.; Jüttner, K.; Li, L.; Mangold, K. M. Fuel Cells 6, (2006) 432.
[2] Kuo, C. W.; Huang, L. M.; Wen, T. C.; Gopalan, A. J. Power Sources 160 (2006) 65.
[3] Patra, S.; Munichandraiah, N. Langmuir 25 (2009) 1732.
[4] Garreau, S. ; Louarn, G. ; Buisson, J.P. ; Froyer, G. ; Lefrant, S. Macromolecules 32, (1999) 6807.
[5] Zhang, L. ; Peng, H. ; Kilmartin, P.A. ; Soeller, C. ; Travas-Sejdic, J. Macromolecules 41, ( 2008) 7671.
60
O17
Electrochemical Hydrogen Loading in Ultrathin Assemblies of Au-Pd Nanostructures
María. G. Montes de Oca and David J. Fermín
*
School of Chemistry, University of Bristol, Cantocks Close, Bristol BS8 1TS, UK
www.chm.bris.ac.uk/pt/electrochemistry/
*
[email protected]
Summary and Objectives
Colloidal based synthetic methods provide delicate control over size, composition and shape of
metallic and bi-metallic nanostructures. These developments have allowed unravelling
fascinating catalytic properties, particularly in system involving Au and Pd nanoparticles [1]. The
present contribution focuses on the electrochemical properties of ultrathin Pd shells grown on
Au nanoparticles towards hydrogen loading. The key objectives of the work include:
•
•
•
Synthesis and characterisation of Pd@Au nanostructures by seeding-growth methods
Two and three dimensional assemblies of the nanostructures via electrostatic layer-bylayer adsorption
Study of the evolution of voltammetric responses associated with hydrogen adsorption
and absorption as a function of the nanoparticle dimensions and the electrode potential
The experimental results demonstrate that layer-by-layer adsorption employing
electrochemically inactive polyelectrolytes generates three dimensional networks of electrically
connected metal nanostructures. The intrinsic high surface area of the 3D assemblies promotes
a significant enhancement of surface sensitive electrochemical responses in comparison to
extended surfaces. This property has lead to the observation of unexpected electrochemical
properties associated with the hydrogen storage in Pd nanoshells. Contrary to experimental
work carried out at thin Pd layers on flat Au surfaces, our results show a large hydrogen
supersaturation for Pd layers of less than 10 nm.
Results and Conclusions
The synthesis of Au-Pd nanostructures involves a two step process initiated by the nucleation of
Au particles with an average diameter of 19.3±1.2 nm employing sodium citrate as reductant
and stabiliser. The second step involves the nucleation of Pd onto as-grown Au colloids by
2reduction of PdCl4 in the presence of ascorbic acid [2]. By controlling the amount of the Pd
precursor added in the second step, the thickness of the Pd layer can be tuned as shown in
table 1. Pd nanoparticles were also synthesised following a similar protocol as for the Au
nanoparticles, yielding an average diameter of 10.1±1.8 nm.
Characterisation of the
monometallic and core-shell nanostructures by HRTEM-EDX, electron diffraction and XRD and
will be presented in this contribution. The results in table 1 also show that the mass ratio of
core-shell nanostructures as expected from the synthesis conditions (first column) closely
matches with the values obtained from EDX.
The sequential electrostatic adsorption of poly-l-lysine (PLL) and the negatively charged metal
nanoparticles leads to the generation of 2D and 3D assemblies as illustrated in figure 1. This
process allows controlling the number density of nanoparticles [3] and the effective surface
roughness of the electrode [4]. Previous studies have demonstrated strong electronic coupling
between nanostructures and metal electrodes linked via ultrathin PLL films [5].
61
O17
Table 1. Dimensions and composition of the synthesised Au-Pd nanostructures
Mass ratio
(synthesis)
Au
Pd20
Au80
Pd40
Au60
Pd60
Au40
Pd80
Au20
Pd
Diameter/nm
19.3 ± 1.2
21.8 ± 1.1
Pd
thickness/nm
--1.3 ± 0.9
24.7 ± 1.3
2.7 ± 1.0
29.5 ± 1.2
5.1 ± 0.9
38.9 ± 1.5
9.9 ± 1.1
10.1 ± 1.8
---A
Mass ratio
(EDX)
--18.7 ± 2.4
81.3 ± 2.4
38.1 ± 1.1
61.9 ± 1.1
57.8 ± 0.9
42.2 ± 0.9
82.1 ± 0.71
17.9 ± 0.71
---B
Figure 1. Two (A) and three (B) dimensional assemblies of citrate stabilised Au nanoparticles generated by electrostatic
layer-by-layer adsorption employing poly-L-lysine.
The electrochemical responses associated with hydrogen loading into the Pd domains in 3D
nanostructured assemblies were investigated in acid solutions. Responses arising from H
adsorption were effectively deconvoluted from the volume dependent absorption. As expected,
the charge originating from H absorption increases as the thickness (volume) of the Pd shell
increases. However, detailed analysis of the hydrogen loading charges vs. the effective surface
roughness revealed unexpectedly high H/Pd ratios which have not been previously reported for
either nanostructured or extended surfaces. The origin of the high H-loading will be discussed in
terms of lattice stress at the Au-Pd boundary. The structure of the ultrathin Pd layer also affects
the energetics associated with the electrochemical formation of atomic layers, e.g. Te
underpotential deposition.
Acknowledgement
We gratefully acknowledge the support by the Mexican National Council for Science and
Technology (CONACYT) and the ESF-COST Action D36/005/06.
References
1. (a) Weijiang Zhou, J. Y. L. Electrochem. Comm. 2007, 9, 1725–1729, (b) A. Sarkany, O. Geszti, G. Safran. App. Cat.
A – General 2008, 350, 157.
2. L. Lehui, H. Wang, X. Shiquan and H. Zhang. J. Mat. Chem. 2002, 12, 156.
3. (a) Zhao J., Bradbury C.R., Huclova S., Potapova I., Carrara M. and Fermín D.J. J. Phys. Chem. B 2005, 109, 22985,
(b) F. Li, I. Ciani, P. Bertoncello, P.R. Unwin, J. Zhao, C.R. Bradbury and D.J. Fermin. J. Phys. Chem C, 2008, 112,
9686.
4. M. Carrara, J.J. Kakkassery, J.P. Abid, D.J. Fermín. ChemPhysChem, 2004, 5, 571.
5. J. Zhao, C.R. Bradbury and D.J. Fermín, J. Phys. Chem. C, 2008, 112, 6832
62
O18
One More Step Closer to Realizing the Dream of the Polymeric RGB Electrochromics
a
b
c*
a
Merve Đçli , Fatih Algı , Atilla Cihaner , Ahmet M. Önal
a
Department of Chemistry, Middle East Technical University, TR-06531 Ankara, Turkey.
Laboratory of Organic Materials, Çanakkale Onsekiz Mart University, TR-17100 Çanakkale,
c
Turkey. Chemistry Group, Faculty of Engineering, Atılım University, TR-06836 Ankara,Turkey. :
*
[email protected]
b
Design, synthesis, and properties of a novel series of donor-acceptor type conducting materials,
namely
poly(4,7-di-2-thienyl-2,1,3-benzoselenadiazole)
(PTSeT),
poly(4,7-di-2,3dihydrothieno[3,4-b][1,4]dioxin-5-yl-2,1,3-benzoselenadiazole) (PESeE) and poly(4,7-bis(3,3didecyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepin-6-yl)-2,1,3-benzoselenadiazole)
(PPSeP)
were highlighted (Chart 1). The role of donor units on the electronic and optical properties of the
conducting polymers was investigated. The unique combination of benzoselenadiazole unit and
electron rich donor units provides an ambipolar (n- and p-doping processes) low band gap
polymers between 1.46 and 1.05 eV and they are exceptionally stable (even after prolonged
standing at ambient conditions). PPSeP is the first processable neutral state green polymer with
three absorption bands that can simultaneously be controlled by an applied potential.
Furthermore, PESeE and PPSeP show electrochromic behaviour with a color change from
green to highly transparent color in an extremely low switching time(0.6 s) during oxidation with
2
a high coloration efficiency (208 cm /C).
C10H21
O
S
O
S
S
N
O
O
S
N
N
Se
C10H21 C10H21
O
O
O
S
N
ESeE
TSeT
O
S
N
Se
C10H21
N
Se
PSeP
Chart 1. 2,1,3-Benzoselenadiazole based D-A systems.
The voltammogram of PseP which was recorded in 0.1 M tetrabutylammonium
hexafluorophosphate (TBAH)/CH2Cl2 (DCM) solution exhibited an irreversible oxidation peak
ox
+
( E m , a ) at 0.50 V vs. Fc/Fc in the positive side, which was attributed to the oxidation of external
red
P units, and a reversible reduction peak ( E m ,1 / 2 ) at -1.64 V in the negative side, which was
ascribed to the radical anion formation from the central 2,1,3-benzoselenadiazole scaffold,
during the anodic and cathodic scans, respectively. These values indicated that the electronic
ox
nature of PseP is between TseT ( E m , a = 0.75 V and
and
E mred,1 / 2 = -1.62 V) and EseE ( E mox, a = 0.35 V
E mred,1 / 2 = -1.72 V), as expected when considering the nature of the D-units.1
The polymerization of PseP to get PPSeP was performed via electrochemically and after
repetitive anodic scans, a new reversible redox couple appeared, which clearly indicated the
formation of an electroactive polymer film on the electrode surface. Also, an increase in the
thickness of the polymer film was confirmed by intensified current after each successive cycle.
The as-prepared polymer film was both green in its neutral state and highly soluble in common
organic solvents such as DCM, CHCl3, diethylether, since processability is vital for the
applications of the neutral state green polymers to electrochromic devices and displays. It is
noteworthy that this rational design where judicious selection of A-parts, in this case P units,
provided access to a unique solution processable neutral state green PEC bearing 2,1,3benzoselenadiazole scaffold. PPSeP exhibited a single and well-defined reversible redox
63
O18
ox
+
couple ( E p ,1 / 2 = 0.16 V vs. Fc/Fc ) which was consistent with the redox behaviours of PTSeT
ox
ox
( E p ,1 / 2 = 0.43 V) and PESeE ( E p ,1 / 2 = -0.59 V).
PPSeP exhibits three absorption bands at 343 nm (3.62 eV), 425 nm (2.92 eV) and 715 nm
(1.73 eV), two of which (<500 nm) absorb the red color and the latter (>700 nm) absorbs blue
(Fig. 1). The band gap (Eg) value for PPSeP on the basis of the low energy end of π-π*
transitions at 715 nm was found to be 1.37 eV which is between the Eg values of PESeE (1.05
eV) and PTSeT (1.46 eV).
Figure 1. Electronic absorption spectra and the colors of the PPSeP on ITO in 0.1 M TBAH/© at various applied
potentials between -0.1 V and 1.1 V.
Gratifyingly, these absorption bands depleted simultaneously upon oxidation with a concomitant
increase of new band in the NIR region which was attributed to the formation of charge carriers
(Fig. 1). These changes in the electronic absorption spectra of PPSeP film were nicely reflected
by a color change from green to almost transparent (See SI-Movie). It is noteworthy that this
color change to transparent is also a quite significant trait in polymeric electrochromic devices
and/or displays along with the green color of the neutral state.
For advanced technological applications, the electrochemical stability of the material upon
switching or cycling is one of the key parameters along with the processability. The polymer film
was quite stable and highly robust since it retained 85% of its electroactivity even after one
thousand of cycles. The electronic absorption spectrum of PPSeP in solution showed
hypsochromic shifts when compared to that of the polymer film on ITO glass slide (in the solid
2
state) which was ascribed to π-π stacking in the solid state.
A novel processable neutral state green polymer (PPSeP) exhibiting low switching time and
exceptional redox stability is highlighted. The polymer film shows electrochromic behavior: a
color change from green to highly transparent color in an low switching time with high coloration
efficiency. Furthermore, it is exceptionally stable even after prolonged standing under ambient
conditions. Studies to get novel neutral state green polymeric electrochromics are under way
and will form the basis of future reports, while the synthesis and engineering of derivatives with
modulated intrinsic properties will also be pursued.
References
[1] A. Cihaner, F. Algı, Adv. Funct. Mater. 18 (2008) 3583.
[2] Jayakannan, M.; Hal, P. A. V.; Janssen, R. A. J. J. Polym. Sci., Part A: Polym. Chem. 2002, 40, 251.
64
O19
Modelling of Au/FeOx interface by in situ Sum Frequency Generation Technique
1
1 2
Z.Pászti , and L. Guczi ,
Chemical Research Center, Institute of Nanochemistry and Catalysis, Hungarian Academy of
Sciences, P. O. Box 17, H1525 Budapest, Hungary, Institute of Isotopes, Hungarian Academy
of Sciences, P. O. Box 77, H-1525 Budapest, Hungary
Abstract
In this work a complex surface analytical unit developed by connection of a multi-technical
surface analysis system and sum frequency generation vibrational spectroscopy (SFG),
provides a unique technique to study interfaces under in situ condition. Preliminary results of
CO adsorption experiments on gold and iron-oxide thin layers grown on gold were presented as
application examples of the experimental setup.
In our previous studies it has been established that the Au/oxide interface played a prevailing
role in the CO oxidation both in model Au/FeOx sytems. It was suggested that the CO activation
occurred at the perimeter of the gold-oxide interface [1-3].
Deeper understanding the processes occurring at interfaces between solid materials and their
environment in situ or even operando investigation techniques, especially in connection with
catalysis related solid-gas interfaces is required [4], where optical spectroscopic methods seem
to provide particularly useful information about adsorption and transformation of the adsorbed
species.
Due to its inherent properties, (SFG) offers new possibilities for exploring gas adsorption
processes and reactions important from the catalytic point of view in model catalytic systems.
In our laboratory we developed a very promising experimental setup by connecting the SFG
spectrometer to a multi-technique surface analysis system via a suitably designed chamber
capable of experiments at elevated pressures equipped a heating/cooling system. Such a
complex instrument allows sample preparation and characterization according to the standards
of traditional surface science as well as in situ determination of the gas
adsorption/transformation properties of the sample at ambient pressure. In this apparatus we
have investigated CO adsorption properties of iron-oxide thin films deposited on gold substrates
(film or single crystal).
SFG is a second order nonlinear optical spectroscopy technique with monolayer sensitivity. The
method is inherently surface/interface specific in most practical cases, as second order
nonlinear optical processes are forbidden in the bulk of centro-symmetric media (e.g. metals,
liquids, gases, etc.), therefore the sum frequency signal is generated only at interfaces, where
the centro-symmetry is necessarily broken. SFG provides characteristic vibration frequencies
resulting from the interfacial species, using two energetic laser beams which have to be
overlapped temporally and spatially at the surface/interface of the sample. One of the exciting
light beams is a tunable IR beam ω IR , the other has a fixed frequency ωVis in the visible.
(
)
(
)
The frequency (photon energy) of the coherently generated outgoing signal beam
equal to the sum of the two exciting frequencies (photon energies) ( ω SFG
(ωSFG )
is
= ω IR + ωVis ). The
sum-frequency intensity is resonantly enhanced when the IR frequency matches the frequency
of a molecular vibration.
100 nm polycrystalline gold film was evaporated onto a Si(100) wafer covered by 100 nm SiO2.
The sample was cleaned by cyclic argon ion bombardment treatments (3 keV, 10 min) in the
analytical chamber of the UHV system at room temperature. The cleanliness of the surface was
checked by UPS and XPS measurements. Iron-oxide layers were formed on the cleaned
-7
support by electron-beam evaporation from an iron rod on 4x10 mbar O2 at room temperature.
The layers were characterized by XPS and UPS measurements.
On CO adsorption on polycrystalline gold in vacuum gives a featureless but relatively intensive
signal was observed, which corresponds to the non-resonant background of the metallic Au
65
O19
-1
substrate. Exposure to 5 mbar CO results in a broad negative going band around 2035 cm and
-1
-1
two narrow bands at 2105 and 2180 cm . While the intensity of the 2035 cm band remains
unchanged up to 10 mbar, the narrow bands become much more pronounced at the higher
pressure. If the chamber is evacuated, all CO related signal disappears. If the temperature is
increased, very little change can be observed even up to room temperature.
Since the gas phase infrared spectrum of molecular CO shows two strong absorption peaks
-1
around 2115 and 2175 cm , it is very probable that the two narrow bands observed in our
spectra are due to the decrease of the intensity of the infrared excitation in those spectral
regions caused by gas phase absorption and are not related to the sum frequency generation
process (the SFG intensity is proportional to the product of the intensities of the visible and
infrared excitations). This assignment is confirmed by the fact that the intensity of these bands
-1
is closely related to the pressure of CO. In the other hand, the 2035 cm band is certainly due
to adsorbed CO. Although this frequency is significantly lower than that usually reported for CO
on supported Au nanoparticles, it is not very far from the value reported for CO on Au(111) in
-1
Ref. [5] (2060 cm ), which was assigned to chemisorbed CO on top sites. In the same work
shifts in the CO frequency to even lower values is predicted for certain crystal planes like (331)
[6].
The gold supported iron-oxide thin film was studied by XPS prior to SFG measurements. A
quantitative evaluation of the intensities of the Fe, O and Au lines performed by the XPS
MultiQuant software indicated that the thickness of the films is around 2 and 8 nm, respectively.
Preliminary SFG results for CO interaction with the 2 and 8 nm iron-oxide films show that peaks
-1
-1
around 2090 cm and a narrower one around 2175 cm . The pressure dependence of this band
confirms its assignation: it is already obviously present at 1 mbar, where the gas phase
absorption related contribution is hardly noticeable. Measurements of the SFG spectra of the
CO stretching region on the 8 nm iron-oxide film were similarly conducted as described for the
bare gold sample. If CO is present in the chamber, the spectra contain the doublet at 2105 and
-1
2175 cm , with higher intensity for higher pressures. If CO is removed, practically no signal is
observable even at low temperatures.
Our data thus indicate that the CO adsorption properties of the 2 and 8 nm iron-oxide layers are
different. Nevertheless, it still remains a question if this difference is connected to the thickness
or the composition of the films, which is in the focus of our current research efforts. In the future
work the single crystal will be investigated.
References
[1] [L. Guczi, D. Horváth, Z. Pászti, L.Tóth, Z. E. Horváth, A. Karacs and G. Petı, J. Phys. Chem B., 104, 3183 (2000),
[2] László Guczi, Gábor Petı, Andrea Beck, Krisztina Frey, Olga Geszti, György Molnár and Csaba Daróczi, J. Am.
Chem. Soc. 125, 4332 (2003)
[3] László Guczi, Krisztina Frey, Andrea Beck, Gábor Petõ, Csaba Daróczi, Norbert Kruse and Sergey Chenakin, Appl.
Catal. A., 291, 116 (2005)]
[4] G. Rupprechter, Catal. Today 126, 3 (2007)
[5] L. Piccolo, D. Loffreda, F.J. Cadete Santos Aires, C. Deranlot,Y. Jugnet, P. Sautet, J.C. Bertolini, Surf. Sci. 566-568,
995 (2004)
[6] T. Keszthelyi, Z. Pászti,T. Rigó,O. Hakkel, J. Telegdi, L. Guczi, J. Phys. Chem. B 110, 8701 (2006)
66
O20
The effect of the Mo precursor on the nanostructure and activity of PtRuMo
electrocatalysts for Proton Exchange Membrane Fuel Cells
N. Tsiouvaras, M.V. Martínez-Huerta, J.L.G. Fierro and M.A. Peña
Instituto de Catálisis y Petroleoquímica, CSIC, 28049 Madrid, Spain
Introduction
The state of the art anodic catalysts for Proton Exchange Membrane Fuel Cells (PEMFC), feed
with H2/CO or methanol in Direct Methanol Fuel Cells (DMFC), are binary catalysts based on
carbon supported PtRu nanoparticles. However, these bimetallic systems are costly and not
efficient enough for its implementation [1, 2]. Exploring ternary PtRuMo catalysts is some of the
most interesting approach for improving their performance. Mo is a transition metal with several
advantages as it has been described extensively in literature in binary PtMo systems, although
the Mo role has yet to be fully determined. Structural characteristics as compositions, chemical
state, degree of alloying, particle size and the stability of Mo in ternary PtRuMo/C systems are
not clear and more studies are necessary in order to further comprehend their full effect in the
CO and methanol electrooxidation.
In the present work the effect of the Mo precursor on the activity for CO electrooxidation has
been investigated. Different Mo precursor as MoCl5, MoO3 and (NH4)6Mo7O24 leads to the
incorporation of different Mo phases as Mo (V), Mo (VI) and Mo (V)/Mo (VI) mixed phases,
respectively. Consequently can alter the surface chemistry of nanoparticles and affect their
electroactivity.
Experimental
For the catalyst preparation a two step procedure has been employed [3]. In a first step the
carbon support was impregnated with the respective Mo precursor in MoO/C, MoNH/C and
MoCl/C supports (see Table 1). In a second step 20 wt. % of PtRu (1:1) has been incorporated
to the Mo/C supports following a colloidal technique. In order to study a representative Mo
phases from each precursor during electrochemical measurements, double amount of Mo was
used with MoO3 precursor (20 wt. %) with respect to other supports (10 wt.%) due to fact that
crystal phases of MoO3 was easily dissolved into the electrolyte (0.5 M H2SO4). Electrocatalysts
as well as support characterization has been carried out through various physicochemical
(XRD, HRTEM, XPS, TPR, TXRF and TG) and electrochemical techniques as cyclic
voltammetries and current-time curves.
Table 1. Prepared materials
Mo Precursor
MoCl5
MoO3
(NH4)6Mo7O24
Mo/C
(Support)
MoCl/C
MoO/C
MoNH/C .
Electrocatalyst
PRMCl
PRMO
PRMNH
Particle size
XRD (nm)
2.6
2.5
2
XRD analysis of Mo/C supports presents no crystal phases in MoCl/C and MoNH/C supports.
However, MoO/C presents diffraction peaks typical of crystalline MoO3. XRD patterns of the
0
ternary samples show the characteristic diffraction lines of Pt metal with a low degree of
crystallinity and the absence of Mo, Ru and crystalline metals oxides. The average particle size
was estimated from XRD patterns (Table 1) and also from TEM images and histograms, and
they are in the range 2-3 nm for all catalysts.
XPS results point that the incorporation of PtRu over different Mo/C supports generate mainly
Mo phases with oxidation states between Mo(V)-Mo(VI), and Mo(VI) phases with lower
contributions in PRMCl and PRMNH catalysts. PRMO show the highest percentage of Mo (VI)
(> 80%).
67
O20
Intensity (A.U.)
TPR analysis of the catalysts presented in Figure 1 show different profiles depending of the
precursor used. The incorporation of Pt and Ru to these supports affects even more greatly
their reduction due to metal interaction phenomena like H2 spill over from the active platinum
sites. In general, TPR peaks between 30 and 70 °C a re due to partially oxidized platinum, and
reduction peaks between 99 and 131 °C correspond to a RuOxHy species. The other peaks in
PRMO and PRMCl are assigned to molybdenum oxide species. In the case of PRMNH the
reduction peaks at different temperatures could indicate particular interaction between
nanoparticles and carbon support with respect to other catalysts
These metal interactions in PRMNH catalyst also
99
cause a shift to lower onset potentials of about 0.1V of
272
the COads oxidation to CO2 compared with PRMCl
40
130
PRMO
(Figure 2). That means that the activity in the CO
60
electrooxidation is higher when ammonium molybdate
PRMCl
271
70
433
is used as precursor. The presence of higher
178
percentage of Mo(VI) in PRMO catalyst decreases
PRMNH
455
dramatically the activity in the CO oxidation
0
200
400
600
800
Temperature (ºC)
Figure 1. TPR analysis of electrocatalysts
80
60
PR MCl
40
20
0
Conclusions
-20
-40
-60
These results clearly demonstrate the importance of
the Mo precursor in the preparation procedure of
ternary electrocatalyst PtRuMo/C and the fact that
highly oxidized molybdenum phases are not
desirable in this kind of systems.
Current (µA)
-80
40
PR MN H
20
0
-20
40
PRM O
20
0
-20
-40
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0 .9
P o te n tia l (V )
Figure 2. CO electrooxidation of atalysts
Acknowledges
This research was funded by the Ministry of Science and Innovation, Spain (Project ENE200767533-C02-01). M.V.M.-H. acknowledges the Ramon y Cajal program of the Ministry of Science
and Innovation of Spain for financial support.
References
[1] Antolini, E. Journal of Applied Electrochemistry 34 (2004) 563
[2] Wee,J.H. and Lee,K.Y. Journal of Power Sources 157 (2006) 128
[3] Martinez-Huerta, M.V., Rodriguez, J.L., Tsiouvaras, N., Peña, M.A., Fierro, J.L.G. and Pastor E., Chemistry of
Materials 20 (2008) 4249
68
O21
Electrocatalytic activity of polypyrrole films incorporating palladium particles
Ana Mourato, Joana S.Cabrita, Luisa M. Abrantes
*
CQB,Departamento de Química e Bioquímica, Faculdade de Ciência da Universidade de
Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
*
luisa.abrantes@ fc.ul.pt
Objective
Displaying a high surface area and providing an efficient route for the flow of electronic charges
to and from the catalyst centres, conducting polymer films have been employed as supporting
matrices for the immobilization of metal particles. For this purpose, chemical or electrochemical
procedures [1,2] can be pursued, including the electroless precipitation, already reported for the
preparation of Polyaniline-Pd composites [3]. This approach, here exploited for the incorporation
of palladium in polypyrrole (Ppy) films, relies on the spontaneous Ppy oxidation and
simultaneous reduction of the metal ions, taking place when the polymer is immersed in a
solution of appropriate pH; the process is auto-sustained as far as the film is exposed to the
metal ion containing solution.
The present work addresses essential aspects in the preparation of electrocatalytic Ppy-Pd
modified electrodes, namely for observing a suitable dispersion of the metal particles deposited
on the polymer matrix.
Results
The polymer features e.g. electroactivity, thickness, porosity and morphology, are imparted by
the electrosynthesis conditions as revealed by the electrochemical (cyclic voltammetry (CV),
electrochemical quartz crystal microbalance (EQCM)) and microscopic (SEM) characterization
of Ppy layers prepared on Pt, under potentiostatic and potentiodynamic control.
The rate and efficiency of the Pd up-take process is determined by the properties of Ppy films
and by the nature and the pH of the palladium ion containing media, as illustrated by the open
circuit potential measurements and EQCM data obtained from PdSO4 and PdC12 solutions. In
the latter case, X-ray photoelectron spectroscopy (XPS) analysis of the loaded polymers shows
that the acidity is crucial to hinder the predominance of Pd(II) species over Pd(0) in the
polymeric matrix.
The electrocatalytic activity of the modified Ppy films towards the anodic oxidation of hydrazine
in KCl solution is also analysed.
Conclusions
The electroless precipitation of Pd on Ppy occurs mainly on the surface of the polymer; although
the size and distribution of Pd particles correlate to the film porosity, an increase in the amount
of polymer is not replicated on the deposited Pd.
For pristine Ppy, under the studied conditions and within 0.0 to 0.6 V vs. SCE potential range,
the response to hydrazine oxidation is featureless, whereas for Ppy-Pd films important catalytic
anodic currents are observed. Notwithstanding care must be taken to avoid a disadvantageous
increase on the number and size of the Pd particles since the best behaviour is attained with
Ppy matrices bearing uniform dispersions of sub-micron Pd particles.
References
[1] M. Ilieva, V. Tsakova, W. Erfurth, Electrochim. Acta, 52 (2006) 816–824.
[2] M. Ocypa, M. Ptasinska, A. Michalska, K. Maksymiuk, E.A.H. Hall, J. Electroanal. Chem., 596 (2006) 157–168.
[3] A. Mourato, A.S. Viana, J.P. Correia, H. Siegenthaler, L.M. Abrantes, Electrochim. Acta, 49 (2004) 2249–2257.
69
O21
70
O22
Bio-inspired electrochemistry: Hydrogen evolution and oxygen reduction at soft
interfaces
Hubert H.Girault – WP7
LEPA, Ecole Polytechnique Fédérale de Lausanne, Lausanne, CH-1015 (Switzerland)
[email protected]
Abstract
As biomembranes, polarised liquid-liquid interfaces provide a spatial separation of reactants
and products and can be the locus of different types of charge transfer reactions such as ion
transfer, acid-base or heterogeneous electron transfer reactions.
Charge transfer at a polarised liquid-liquid interface: a) ion transfer reaction, b) assisted proton transfer reaction and c)
hetero-geneous electron transfer reactions between an aqueous acceptor O1 and a lipophilic donor R2
As with biomembranes, all those different reactions are coupled. By controlling the polarisation
of the interface, and to a certain extent the potential distribution across the interface, we have
an electrochemical control of the different reactions.
Electrochemistry at the Interface between Two Immiscible Electrolyte Solutions (ITIES) has
developed over the last decades as a rather well characterised field of research. From a charge
transfer viewpoint, most of the electrochemical methodologies developed to study charge
transfer reactions at solid electrodes have been transposed taking in to account the different
types of mass transfer processes.
Recently within the project D36-WP7, we have developed the concept of electrocatalysis at
ITIES using porphyrins as electrocatalysts for oxygen reduction [1]. In particular, we shall
discuss proton coupled electron transfer reactions at ITIES that are relevant for energy
research. Results with different porphyrins including free base porphyrins will be presented.
Oxygen reduction catalysed by CoTPP with electro-chemical proton pumping
Finally we have also shown that the protonation of decamethylferrocene at ITIES leads to the
production of hydrogen in anaerobic conditions [2], and to the production of hydrogen peroxide
71
O22
in the aerobic case (see below) [3]. We shall show how voltammetry at ITIES can be used to
elucidate the reaction mechanism.
Oxygen reduction by decamethylferrocene (DMFc) control-led by proton transfer reaction. The liquid|liquid interface is
pola-rised by the choice of the hydrophilic salt lithium tetra(pentafluoro-phenyl)-borate (LiTB) and of the lipophilic salt
bis(triphenylphos-phoranylidene)ammonium tetra(pentafluorophenyl)borate (BATB)
References
[1] R.P. Nia, B. Su, F. Li, C.P. Gros, J.-M. Barbe and H.H. Girault, Chem. Eur. J., 2009, 15, 2335
[2] I. Hatay, B. Su, F. Li, R. Partovi-Nia, H. Vrubel, X.L. Hu, M. Ersoz and H. H. Girault, Angew. Chem., 2009, 48, 5139
[3] B. Su, R.P. Nia, F. Li, M. Hojeij, M. Prudent, C. Corminboeuf, Z. Samec, and H. H. Girault, Angew. Chem., 2008, 47,
4675
72
O23
Density functional and electrochemical studies of the catalytic ethylene oxidation on
nanostructured Au and Pt electrodes.
J. Šebera, P. Krtil, Z. Samec and S. Záliš
*
J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic,
Dolejskova 3, CZ 18223, Prague, Czech Republic
*
[email protected]
Objectives
There is a need to develop electrocatalytic materials appropriate for oxygen insertion reactions
to double bonds [1]. Specific reactivity could be achieved using metal nanostructured
electrodes. Experimental studies indicated the preferable carbon dioxide formation in the case
of the oxidation of ethylene and propylene on platinum, the same processes on gold surface
yields a mixture of partially oxidized product. The current understanding of these reactions is, at
present, rather limited. Considering these limitations of the state of the art, the research
program for investigation of fundamental aspects of reactivity at bulk gold and platinum
nanostructured electrodes is desirable. Theoretical calculations of reactivity and the potential
energy curves for different reactant and product conformations would be done. This work
addresses theoretical aspects of the electronic structure of reaction intermediates, ionic
distribution at the cluster – solution interface and the more fundamental aspects of looking for
transition states in order to map the reaction coordinate of reactions that takes place in ethylene
oxidation at metal nanoparticles, modeled by Aun and Ptn (n=10-25) clusters.
Results
DFT method was used for the
modeling of gold and platinum
clusters up to size Au25 and Pt25 and
their
interaction
with
organic
molecules. The mechanisms of the
O and C2H4 adsorption at the metal
clusters of varying size, the
formation of Mx-Et-O intermediates
and the possible intermediate
transfer under the influence of
electric field or electrode reaction
were studied. During the geometry optimization and transition structure search the geometry of
clusters was fixed, the remaining part was fully optimized. By the interaction of the adsorbed
oxygen with ethylene the stable surface oxametallacycle intermediates are formed analogously
to ones described in the case of ethylene oxide reaction at Ag(111) surface [2]. The interaction
with the surface depends on the type of the cluster, its size and the reaction site (the plane
steps or edges). Figure shows the oxametallacycle intermediate on Au22 (left) and Pt21 (right). In
the case of catalysis on gold, the transition state leading to oxirane lies 11.7 kcal/mol above the
energy of the intermediate, the formation of acetaldehyde is barrierless. The results of the DFT
calculations are in accordance with experimental results of electrocatalytic oxidation of ethylene
on both gold and platinum. The on-line differential electrochemical mass spectrometry (DEMS)
identifies in the case of oxidation on gold preferential formation of acetaldehyde (with carbon
dioxide forming a minor reaction product); in the case of Pt electrodes the reaction produces
solely the carbon dioxide. In both cases the oxidation processes gets inhibited by the metal
surface oxidation and is accompanied with metal dissolution.
The geometry of the intermediates is only slightly influenced by the static electric field
corresponding to the electrochemical potential around 1 V or by the influence of solvent cavity.
External effects more strongly influence transition states geometries and energetics.
73
O23
Conclusions
The anodic oxidation of ethylene on gold nanostructures leads to a formation of acetaldehyde
as a major product. In the case of platinum the ethylene oxidation proceeds carbon dioxide is
almost quantitatively formed. DFT calculations support experimental findings and indicate
possible reaction mechanisms of catalytic reactions. DFT calculations points to the different
reactivity on individual types of surfaces and different types of clusters.
Acknowledgements
This work was supported by COST D36 action and the Academy of Sciences of the Czech
Republic (grant KAN100400702).
References
[1] S. Otsuka, I. Yamanaka, Catalysis Today 41 311 (1998).
[2] S. Linic, M.A. Barteau, J. Am. Chem. Soc. 124 310 (2002).
74
O24
An FTIR study of ternary PtSn-Rh/C for ethanol electrooxidation: effect of surface
composition
a
a,*
a
a
b
S. García-Rodríguez , S. Rojas , M.A. Peña , J.L.G. Fierro , S. Baranton , J.-M. Léger
b
a
Estructura y Reactividad de Catalizadores; Instituto de Catálisis y Petroleoquímica, CSIC
c/ Marie Curie 2, 28049, Madrid, Spain.
b
LACCO,, Equipe Electrocatalyse, UMR 6503 CNRS, Université de Poitiers, 40, av. du Recteur
Pineau 86022 Poitiers Cedex, France
π. [email protected]
Objective
In this work, functional materials with catalytic interest in the electrooxidation of ethanol are
studied by operando infrared techniques. A series of supported binary (Pt-Sn) and ternary (PtSn-Rh) nanostructured materials supported on carbon were studied by Single Potential
Alteration Infrared Reflectance Spectroscopy (SPAIRS) and Substractively Normalized
Interfacial FTIR Spectroscopy (SNIFTIRS). This techniques allows the study of the double layer
at the metal/solution interface. Results are then correlated with surface composition obtained by
XPS and structural characterization (XRD and analytical microscopy). Addition of Rh to PtSn/C
containing the Pt3Sn alloy phase seems to enhance ethanol electrooxidation at low potential
provided Rh content is kept around 1%wt.
Experimental
Catalyst preparation
PtRh/C and PtSn/C samples were prepared by conventional impregnation-reduction method. An
aging step is required to avoid loss of volatile tin chlorides during the thermal treatments.
Ternary samples were prepared by successive impregnation of the PtSn/C sample with a water
solution of rhodium trichloride and subjected to the same thermal treatment. Total metal loading
is 40%wt. Atomic Pt/Sn = 3:1, and Rh content is 3%wt in PtRh/C sampe and between 1 and 3
%wt in ternary samples.
Electrochemical experiments and In situ IR reflectance spectroscopy measurements
-1
IR reflectance spectra in the wavenumber region 1000-3000 cm were collected by a Fourier
transform infrared spectrometer (Bruker IFS 66vs) with an incidence angle of 65º, after passing
through the IR window (CaF2) of a conventional thin layer spectrochemical cell, using a
Reversible Hydrogen Electrode (RHE), a gold wire and a gold disk as reference, counter and
working electrodes, respectively. This apparatus was equipped with a spectral reflectance
device allowing the observation of reflectance spectra of the electrode-electrolyte interface with
the IR light beam passing entirely through a chamber under vacuum. Electrode reflectivity REi
-1
was recorded at different potentials, Ei, each separated by 50 mV at a sweep rate of 1 mV·s . A
positive absorption band indicates the consumption of species and a negative absorption band
means the production of species.
Results
Bimetallic PtRh/C samples resulted much less active than PtSn/C for the electrooxidation of
ethanol. The addition of Rh to PtSn/C resulted in an increase in the performance of the catalyst
at potentials less positive than 0.6 V [1,2]. Figure 1a shows forward scans of the linear
voltammograms of the catalysts in 0.1 M HclO4 and 0.1 M EtOH. The current densities recorded
for the ternary samples are the highest of the series. The performance of PtSn-1Rh/C is the
best of the series at every recorded potentials, while that of the ternary sample with higher Rh
content, PtSn-3Rh/C drops below that of PtSn/C at E ≥ 0.6 V. We used SPAIRS technique to
identify reaction intermediates and products of ethanol electrooxidation. Figure 1b shows a set
of representative SPAIR spectra of the species resulting of the oxidation of ethanol on PtSn1Rh/C. The band at 1115 is attributed to the adsorption of the electrolyte. Bands at around
1293, 1393 and 2620 cm-1 correspond to the coupling between the elongation vibration ν(C-O) of
75
O24
the C-O bond, the deformation mode δ(OH) of the –COOH group of acetic acid, and the
-1
vibration νCH, respectively. The intense band at 1715 cm is assigned to the stretching mode
ν(CO) from the carbonyl group [3]. The presence of this band is associated to the existence of
intermediates adsorbed over the catalyst similar to acetaldehyde. The bands at 2343 and 2048
-1
cm are due to CO2 and CO, respectively. These two bands are more clearly seen in the
SNIFTIRS spectra in Figure 1c.
Pt3Sn
0.5
-1
-1
2620 cm
-1
1293 cm
-1
1394 cm
100 mV
0.4
200 mV
0.3
400 mV
500 mV
600 mV
700 mV
a)
0.1
800 mV
b)
c) d)
900 mV
-1
0.0
0.0
2343 cm
0.2
0.4
0.6
0.8
E / V vs RHE
1.0
e) f)
-1
1715 cm
-1
1115 cm
0.01
3000
∆ T/T
0.2
(RE2-RE1) /RE1
300 mV
Transmittance
-2
i / mA·cmgeom
2048 cm
2500
2000
1500
1000
Wave number / cm-1
2500
2000
2500
2000
2400 2000
2400 2000
Wave number / cm
Wavenumber / cm-1
Figure 1. a) Forward potential scan at 0.1 mV/s in 0.1 M HclO4 and 0.1 M EtOH solution of PtSn/C (black solid), PtRh/C
(gray solid), PtSn-1Rh/C (black dashed) and PtSn-3Rh/C (gray dashed); b) SPAIRS spectra recorded from the PtSn1Rh/C at the same conditions that in Figure 1a; SNIFTIRS spectra of a selected region of the spectra comprising Co
and CO2 bands obtained from the electrooxidation of ethanol with: c) PtSn/C, d) PtSn-1Rh/C, e) PtSn-3Rh/C, and f)
PtRh/C, recorded at the same conditions that Figure 1a.
Conclusions
Addition of Rh enhances the performance of PtSn/C for ethanol electrooxidation. According to
SPAIRS data, Rh may promote the appearance of carbonyl species on the surface of the
catalyst, while tin oxidize CO species.
References
[1] S. García-Rodríguez, F. Somodi, I. Borbáth, J.L. Margitfalvi, M.A. Peña, J.L.G. Fierro, S. Rojas, Appl. Catal. B, In
press.
[2] A. Kowal, M.Li, M. Shao, K. Sasaki, M.B. Vukmirovic, J. Zhang, N.S. Marinkovic, P. Liu, A.I. Frenkel, R.R.Adzic,
Nature Materials, 8 (2009) 325.
[3] F.L.S. Purgato, P. Olivi, J.-M. Léger, A.R. de Andrade, G. Tremiliosi-Filho, E.R. Gonzalez, C. Lamy, K.B., Kojoh, J.
Electroanal. Chem. 628 (2009) 81.
76
O25
Adsorption of proteins on DLC surfaces
1
2
2
V. Ribitsch , M. Reischl , B. Pointner , K. Stana-Kleinschek
3
1
University Graz, Institute of Chemistry, [email protected]
Joanneum Research, Inst. Of Chemical Process Development and Process Control Austria,
[email protected], [email protected]
3
University Maribor, Institute of Engineering Materials and Design, Slovenia,
[email protected]
2
Objective
Diamond like carbon (DLC) layers are suggested to reduce essential non-selective protein
adsorption of polymer materials used as medical implants. We investigated the protein
adsorption on several DLC layers produced under different conditions (without and with N2 and
Ar plasma treatment and sputtered with Ti) to gain different hydrophilic and hydrophobic
surfaces. The DLC layers were applied to glass and PET surfaces. Contact angle, fluorescent
spectroscopy, electrokinetic methods, fluorescent microscopy and QCM quartz micro balance
were applied to characterize the surface properties and the protein adsorption kinetics.
Results
The protein adsorption is an entropy and enthalpy driven two step processes. A first fast and
reversible process is followed by a slow conformation change leading to an irreversible
adsorption. The adsorption kinetics is not much influenced by DLC coating compared to glass or
PET surfaces but the amount of adsorbed protein is reduced by a factor 2,5 by the DLC coating
independent of the substrate. The electrokinetic experiments show that both, the DLC layers as
well as the proteins are negatively charged at pH 7.3. Nevertheless the electrostatic repulsion,
screened by high ionic strength does not suppress adsorption. Hydrophobic interactions of nonpolar segments are the driving forces. Proteins with a strong inner structure (hard proteins,
Lysocyme) show less adsorption on hydrophilic then on hydrophobic surfaces, soft proteins
(BSA) adsorb on all surfaces independent on the surface thermodynamics. This difference is
caused by the entropy increase due to conformational changes.
The protein adsorption and the rigidity of the adsorbed film were measured using fluorescent
microscopy and QCM. The obtained results show the following characteristics:
Extremely hydrophilic DLC-surfaces having a contact angle between 16° to 20° show an IEP of
2
2,5 and the smallest protein affinity of 10% compared to reference glass (5mg/cm ).
The protein adsorption of less hydrophilic DLC-surfaces with contact angles between 25° to 30°
causes a shift of the IEP towards 4.4. The amount of adsorbed protein is between 15 – 25% of
that of reference glass.
In the case of hydrophobic DLC layers (contact angle between 55° to 80°) an IEP shift to 4.8 is
observed and the amount of adsorbed protein is 55% to 70% of the reference surfaces.
77
O25
Conclusions:
Changes of spectroscopic parameters in the solution are almost not observable due to the small
amount adsorbed on the solid phase.
A direct observation of the amount of adsorbed protein is not possible in the case of soft
proteins due to their structural changes after adsorption.
The adsorption is directly observable using streaming potential and QCM. The isoelectric point
is significantly shifted with increasing adsorption. QCM experiments describe the amount as well
as the adsorbed layers structural properties.
Zetapotential [mV]
40
20
no BSA
BSA 2*10 Mol/l
BSA 8*10 Mol/l
BSA 1*10 Mol/l
0
-20
-40
-60
2
3
4
5
6
7
8
9
10
pH
Figure. Zetapotential vs. pH of DLC- layers after adsorption of BSA in 67 mM Phosphat, pH 7.4, different protein
concentrations
78
O26
Amino Acid-Based Biocompatible Surfactants
Mª Rosa Infante, Lourdes Perez, Aurora Pinazo, MªCarmen Moran, Ramon Pons, Mª
1
Teresa Garcia, Mª Pilar Vinardell
IQAC-CSIC, Jordi Girona 18. 08008 Barcelona
Facultad de Farmacia. Universidad de Barcelona
1
There is a pressing need for developing efficiently surfactants that are biodegradable and
biocompatible. Surfactant molecules from renewable raw materials that mimic natural lipoamino
acids are one of the preferred choices for food, pharmaceutical and cosmetic applications.
Given their natural and simple structure they show low toxicity and quick biodegradation. The
value of amino acids and vegetable oil derivatives as raw materials for the preparation of
surfactants was recognized as soon as they were discovered early in the last century. The
combination of polar amino acids/peptides (hydrophilic moiety) and non-polar long-chain
compounds (hydrophobic moiety) for building up the amphiphilic structure has produced
molecules with high surface activity. Our group has a wide experience in synthesis (chemical,
enzymatic or, usually, by a combination of both methodologies) of amino acid-based surfactants
obtained from the combination of natural saturated fatty acids, alcohols and amines with
different amino acid head groups through ester and amide linkages. Thus, saturated singlechain, double-chain, and iusep surfactants of different ionic character have been found to be
in all cases highly biodegradable, with low toxicity, ecotoxicity and irritation effects.
Water solubility and self-aggregation properties were directly associated with the chemical
structure of the molecule and only cationic lipoamino acids possessed antimicrobial activity.
Their multifunctional performance makes amino acid based surfactants a valuable high added
value compounds from renewable raw materials for potential multipurpose new applications in
bio/nano materials and biomedicine.
79
O26
80
O27
Interactions of DNA with cationic surfactants and proteins: Gels, gel nano-particles,
microstructure and phase separation
Björn Lindman, Maria Miguel, Rita Dias, Diana Costa, Dan Lundberg and Carmen Moran
Physical Chemistry 1, Lund University, POBox 124, SE-221 00 Lund, SWEDEN, and
Department of Chemistry, Coimbra University, Coimbra, PORTUGAL
Cationic polymers and surfactants are efficient in compacting DNA and can also be efficient
transfection agents. These systems are also characterized by a strong associative phase
separation. In attempts to mimic the DNA-histone interactions in chromatin, the phase
behaviour and aggregate structure in different aqueous mixtures of DNA and a cationic protein
were investigated. We also describe the preparation of covalent DNA gels and describe their
swelling-deswelling behaviour. It is found that covalent gels offer novel opportunities for
monitoring DNA-cosolute interactions. Based on the associative phase separation, the
preparation of novel DNA particles by mixing DNA and surfactant solutions can be achieved; the
size of the gel particles can be controlled from ca. 100 nm and upwards. The properties and
DNA release characteristics of these particles are also described. A local phase separation in
covalent gels can lead the formation of a surface phase, a “skin”. The different types of studies
are performed for both double- and single-stranded DNA. Throughout, a stronger interaction is
observed with denatured DNA. On the basis of these results and other observations it is found
useful to view DNA as an amphiphilic polymer self-assembling by hydrophobic interactions.
81
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82
O28
Symmetry-asymmetry effects on the self-assembly of
ion-paired surfactant systems
1
1
1
Eduardo F. Marques , Bruno Silva , Rodrigo Brito , Ulf Olsson
2
1
Centro de Investigação em Química, Department of Chemistry, Faculty of Science, University
of Porto.
2
Physical Chemistry, Centre for Chemistry and Chemical Engineering, Lund University,
Sweden.
In this talk, we will discuss the effect of chain length symmetry or asymmetry on the aqueous
bulk behaviour of mixtures of cationic and anionic surfactants (ion-paired systems), through a
brief revision of systems recently studied in our group. Both conventional amphiphiles of
commercial origin and novel amino acid based amphiphiles will be considered.
+
-
For salt-free alkyltrimethylammonium alkylsulfonates of the type Cm Cn , we will see that they
+
can be water soluble at or near room temperature if the chain length difference between Cm
and Cn is high [1], i.e. if m>>n or n>>m. This is a consequence of the solubility mismatch that
originates a variable surface charge density in the aggregates, according to a charge regulation
+
mechanism[2]. We compare different binary C16 Cn /water systems where n is varied from 6 to
10. A peculiar consequence of this concentration-dependent charge density is the coexistence
of a dilute and a concentrated lamellar phases. At low concentration, stable vesicles are formed
and when temperature is changed, an unusual vesicle-to-micelle transition occurs, involving in
both directions the formation of lamellar domains as an intermediate structure.
With respect to more bio-friendly systems, based on lysine- and serine-derived surfactants, two
pair systems were studied, one symmetric with C12/C12 chains and one asymmetric, with
C8/C16 chains (where the Ser-derived surfactant has the longest chain) [3]. Different vesicle
size and mechanisms of the vesicle-to-micelle transition have been found. The results are
discussed on the basis of models for the micelle-vesicle transitions and the equilibrium
stabilization of vesicles (spontaneous curvature energy, bending moduli and translational
entropy).
References
[1] Silva, B. F. B.; Marques, E. F.; Olsson, U., Langmuir 2008, 24, 10746.
[2] Silva, B.F.B; Marques, E.F.; Linse, P; Olsson U., J. Phys. Chem. B, 2009, 113, 10230.
[3] Marques, E.F.; Brito, R.O.; Silva, S.G.; Rodríguez-Borges, J.E.; Vale, M.L.; Gomes, P.; Araújo M.J., Langmuir 2008,
24, 11009.
83
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84
O29
Formic Acid as a Hydrogen Source for Vapor Phase Catalytic Reactions
Dmitri A. Bulushev* and Julian R.H. Ross
Charles Parsons Initiative, CES, University of Limerick, Limerick (Ireland)
*[email protected]
Introduction
There is currently a great deal of interest in the development of so-called “Second
Generation” bio-refining processes, an example being the Biofine Process. This transforms
cellulosic biomass feedstock by acid catalyzed hydrolysis to give a mixture of levulinic acid and
formic acid (FA) together with a “char” residue [1]. The levulinic acid can be used for the
production of chemicals and transport fuel additives. We are currently examining potential uses
of the FA produced. For example, FA can be decomposed over a variety of different catalysts to
give hydrogen and CO2; the aim is to find catalysts to optimize hydrogen production with a
minimum of CO production.
As part of our study, we have examined the possibility of using formic acid as a direct source of
hydrogen in hydrogenation reactions, thus avoiding the separate step of hydrogen production.
To test this idea, we have examined the use of FA in the hydrogenation of ethylene and
propylene over a number of catalysts (reactions 1 and 2):
HCOOH + C2H4 CO2 + C2H6
HCOOH + C3H6 CO2 + C3H8
(1)
(2)
Materials and Methods
Several different materials (for example, 10 wt% Pd/C (Degussa), 1 wt% Au/C (WGC),
1 wt% Au/TiO2 (WGC), 1 wt% Pt/ZrO2) were tested for both FA decomposition and the direct
hydrogenation of olefins (C2H4, C3H6) by FA. The catalysts were placed in the quartz tubular
reactor of a microreactor system, then pretreated in a 1% H2/Ar mixture at 573 K for 1 h and
cooled in He to reaction temperature. The reaction products were analyzed by GC.
Results and Discussion
Good results were obtained with a number of catalysts and will be reported. However,
only the results for the Pd/C catalyst will be shown here since this material gives the best results
obtained for both FA decomposition and the hydrogenation of the olefins. A very small amount
of this catalyst (6 mg) gave decomposition of FA to hydrogen and CO2 at temperatures as low
as 358-433 K. Furthermore, C2H4 (see Fig. 1) as well as C3H6 (not shown) could be
hydrogenated effectively by FA over the same range of temperatures. No deactivation was
observed. Complete conversion of the FA was achieved at about 433 K. The undesirable CO
production was almost completely eliminated, the selectivity to CO2 being very high (Fig. 1).
Generally, the products of the Biofine process contain significant amounts of water and so that it
is important that the FA reactions will occur in the presence of water iusep. It was found that
water iusep has a small positive effect on both FA decomposition (not shown) and C2H4
hydrogenation by FA (Fig. 1).
It is suggested that the mechanism involves two important steps: the formation of adsorbed
hydrogen from FA and its consumption by the olefin. That the second step is probably fast was
shown by the observation that the olefins examined could both be hydrogenated by hydrogen
with 100% conversion even at 313 K over the Pd/C catalyst. Thus, hydrogenation by molecular
hydrogen is more effective than that by FA, the rate of the latter reaction being determined by
the rate of production of surface hydrogen.
85
O29
Conclusions
It has been shown that olefins can be hydrogenated effectively in the iusep phase by
using FA instead of hydrogen. This means that the separate step of hydrogen production as
well as the need for hydrogen storage and transportation can both be eliminated. It may also be
possible to use FA as a hydrogen source for some of the hydrogenation steps in the conversion
of levulinic acid to fuel additives and this is being examined. The method may also have
applications in other hydrogenation reactions.
1
CO2 selectivity,
HCOOH conversion,
0.8
0.6
HCOOH+H2O+C2H4
HCOOH+C2H4
0.4
HCOOH
HCOOH+H2O
HCOOH
0.2
0
0
50
100
150
200
time, min
Figure 1. Comparison of the HCOOH conversion and CO2 selectivity with different gas compositions: (2.4% HCOOH,
2.4% HCOOH/2.3% H2O, 2.4% HCOOH/2.3% H2O/1% C2H4, 2.4% HCOOH/1% C2H4, 2.4% HCOOH, balance He) over
a 10 wt% Pd/C catalyst (total flow rate 51 ml/min, reactor temperature 388 K)
References
[1] Hayes, D. J.; Fitzpatrick, S.; Hayes, M. H. B.; Ross, J. R. H., The Biofine process - Production of Levulinic Acid,
Furfural, and Formic Acid from Lignocellulosic Feedstocks. In Biorefineries-Industrial Processes and Products, Kamm,
B.; Gruber, P. R.; Kamm, M., Eds. Wiley-VCH: Weinheim, 2006; Vol. 1, pp 139-164.
86
BOOK OF ABSTRACTS
Section IV:
Poster
Communications
P1
Silylation of functionalized commercial silica for the direct synthesis of hydrogen
peroxide solution
1
1
2
G. Blanco Brieva , J. M. Campos-Martin , M. P. de Frutos and J. L. G. Fierro
1
1
Instituto de Catálisis y Petroleoquímica, CSIC, Marie Curie, 2, Cantoblanco, 28049 Madrid,
Spain
2
Centro de Tecnología Repsol YPF, A-5, Km. 18, 28931 Móstoles, Spain
Introduction
Hydrogen peroxide (H2O2) is a clean oxidizing and bleaching agent that is used for water
purification/wastewater treatments, as whitening agent, disinfectant and as basic product of the
chemical industry [0]. Efforts are therefore being made to replace H2O2 production by the
standard anthraquinone process because of its high cost does not allow the H2O2 to be used for
the production of bulk organic chemicals. Thus, the synthesis of H2O2 by direct reaction
between H2 and O2 appears quite advantageous to conventional process. Acids are often
incorporated into the reaction medium to delay or prevent the decomposition of H2O2, which
indeed takes places in the presence of bases [0]. To yield H2O2 formation, some halides are
often added to delay water production with the subsequent increase in H2O2 selectivity [0,0].
Recently, we have shown that the liquid-phase direct synthesis of hydrogen peroxide can be
achieved using palladium nanoparticles deposited on sulphonic acid functionalized silica
catalysts [0]. A recent report emphasized the strong effect of surface modification on the
selectivity to hydrogen peroxide [0]. Based on these previous works, this work was undertaken
with the aim to study the effect of silylation of surface modification of sulphonic acid
functionalized by silylation, use these modified supports to prepare based Pd catalysts for direct
synthesis of H2O2 in non acidic solutions. This surface modification can produce a more
hydrophobic surface which can avoid secondary reactions.
Experimental section
Firstly, to a suspension of functionalized commercial silica (Silycicle Tosic Acid) (10 g.) in
toluene (100 ml), Cl-Si-(CH3)3 or CF3(CF2)5-(CH2)2Si(CH3)2Cl was added drop by drop. The
suspension was stirred for 6 h under reflux. Then the remaining solution was filtered off and the
solid obtained was washed with toluene (50 ml) followed by air-drying at 373 K for 12 h. A
reaction scheme of the silylation procedure and sample labelling is shown in Figure 1.
R
SO3 H
Si
Si
O
O
O
O
Cl-Si-(CH3)3
SiCoCl
CH2-(CF2)5-CF3
Si
+
C10H10 ClF13 Si
OH
O
O
R
O
Si
O
O
HCl
Si
O
O
SiCo
SiCoPF
Figure 1 Schematic modification of the silica functionalized support.
Modified support (10 g) was stirred with 125 ml of acetone. To this suspension, a palladium (II)
acetate (Johnson Matthey) solution in acetone (50 ml) was added drop by drop. The suspension
was stirred for 1 h. The remaining solution was filtered off and the solid obtained was washed
and air-dried at 333 K for 2 h. Supports and catalysts were characterized by several techniques,
N2 isotherms, TGA, FTIR and XPS. Catalysts were tested in the direct synthesis of H2O2. In a
typical run, 1.6 g of the catalyst was put inside an autoclave with 150 g of methanol and HBr as
promoter. The reactor was pressured with N2 to 9.5 Mpa. The mixture was heated to 313 K.
Then, the reaction gas mixture was feed (H2:O2:N2 (3.6:46.4:50)) with a total flow of 2500 mlN
min-1 without stirring, and then stirring was started up (1500 rpm) to initiate the reaction.
89
P1
Thermogravimetric profiles of SiCo, SiCoCl and SiCoPF show that water desorption occurs at
temperatures lower than 383 K and the extent of water desorption is smaller in SiCoCl and
SiCoPF samples whose surface has been made hydrophobic. Nitrogen adsorption-desorption
isotherms show that the addition of silane precursors led to a decrease in adsorption capacity
respect the silica reference (SiCo). The reduction of the adsorption capacity of functionalized
silica samples is clearly illustrated by the decrease in specific area. Pore volume increases due
to a good sililation, with the exception of SiCoPF because of the size of the silane precursor
employed does not allow the surface to be effectively silylated. Both chemical state and relative
abundance of palladium species of the catalysts was determined by XPS. The Pd 3d core-level
spectra present the characteristic spin–orbit splitting of Pd 3d levels. By applying peak fitting
procedures each component of the Pd 3d doublet, two palladium components were obtained:
one at 336.5 eV, is characteristic of PdO clusters, and another at 338.2 eV, which corresponds
II
to Pd ions interacting with the –SO3H groups of the silica. It has been demonstrated that the
II
catalyst containing a higher amount of Pd ions interacting with –SO3H groups than PdO
(amount of these, depend on Pd content) afford a high selectivity and conversion of H2O2 in
II
liquid phase [0,0]. Pd-SiCoCl and Pd-SiCoPF show less amount of Pd ions interacting with –
SO3H than Pd-SiCo. Pd-SiCoPF exhibit a large percentage of PdO clusters (85%). The
concentration profiles of H2O2, Figure 2, are almost linearly dependent on the time of reaction,
indicating that reaction proceeds at a constant rate. The H2O2 production rate was very high and
clearly higher for PdSiCo than the other two catalysts. The activity data are in good agreement
with the nature of the Pd species, as revealed by XPS. The catalyst with the lowest proportion
II
of PdO, and hence with the highest amount of Pd ions interacting with –SO3H groups
(PdSiCo), afford the highest selectivity and highest concentration of H2O2 in the liquid phase. A
similar effect, although less marked, was noted for PdSiCoCl catalyst in which activity is lower
than in PdSiCo even though the slopes of the straight display are similar.
80
9
PdSiCo
Pd-SiCoCl
Pd-SiCoPF
8
70
60
7
% Selectivity to H2O2
Wt % H2O2
6
5
4
3
50
40
30
20
2
PdSiCo
Pd-SiCoCl
Pd-SiCoPF
10
1
0
0
0
20
40
60
80
Time (min)
100
120
0
20
40
60
80
100
120
Time (min)
Figure 2 H2O2 concentration and selectivity profiles versus reaction time along the direct reaction of hydrogen and
oxygen at 313 K.
PdSiCoCl catalyst shows the lowest selectivity because, in this case, silylation becomes highly
effective and transport phenomena between reagents (H2 and O2) and the catalyst surface take
place. Finally, it is concluded that silylation of the catalyst surface reduces to some extent both
productivity and selectivity to hydrogen peroxide.
References
[1] G. Blanco-Brieva, J. M. Campos-Martin and J. L. G. Fierro, Angew. Chem. Int. Ed., 2006, 45, 6962.
[2]R. Burch and P. R. Ellis, Appl. Catal. B: Environ., 2003, 42(2), 203.
[3] G. Blanco-Brieva, E. Cano-Serrano, J. M. Campos-Martin and J. L. G. Fierro EP2000205A1 (2008), assigned to
Repsol Química, S.A.
[4] J. K. Edwards, B. Solsona, E. Ntainjua, A. F. Carley, A. A. Herzing, C. J. Kiely, G. J. Hutchings, Science 2009, 323,
1037
[5] G. Blanco-Brieva, J. M. Campos-Martin and J. L. G. Fierro, Chem iuse., 2004, 1184.
[6] G. Blanco-Brieva, M. C. Capel-Sanchez, M. P. de Frutos, J. M. Campos-Martin and J. L. G. Fierro, Ind. Eng. Chem.
Res., 2008, 47, 8013.
90
P2
Attempts to Understand the Enantioselectivity of Chiral Propylene Oxide Adsorption on
NEA-Modified Pt Surfaces
1
1
2
2
J.L. Sales , V. Gargiulo , I. Lee , F. Zaera and G. Zgrablich
(1)
1*
Instituto de Física Aplicada (INFAP), CONICET-UNSL, San Luis, Argentina.
Califórnia, Riverside, USA.
*
[email protected]
(2)
University of
Objective
Experimental propylene oxide (PO) TPD data from PO (R or S) adsortbed on Pt surfaces with
different (S)-1-(1-naphthyl)ethylamine (NEA) coverages [1] are shown in Figure 1. The behavior
seen in these TPD spectra is quite complex, with two well-separated groups of peaks indicating
the presence of two energetically distinct desorption states. The most surprising feature of these
TPD spectra is that, as the NEA coverage on the surface increases steadily, the PO coverage
does not follow the expected uniform decrease: it does start decreasing at low NEA coverage,
but then increases suddenly at intermediate coverage and reaches a local coverage maximum
before decreasing again. We refer to this behavior as the “regression effect,” and note that it
occurs only for PO(S), i.e. PO of the same chirality of the NEA modifier. This regression effect
can be seen clearly in Figure 1 (a), and is responsible for the enantioselectivity peaks shown in
Figure 1 (b). Much effort was placed in simulating this behavior on the basis of pair-wise
interactions between PO and NEA molecules on the surface, but those failed in reproducing
even the crudest features of the experimental results. Therefore, it was concluded that the
observed behavior must be the result of a cooperative effect: under the presence of some
configurations of NEA and PO the surface energetics is proposed to be locally modified in such
a way as to become selective toward the (S)-PO enantiomer. In addition, the creation of
forbidden sites for the adsorption of PO is absolutely necessary in order to produce the
observed regression effect in TPD spectra (see below).
With these considerations in mind, some models are proposed and discussed as an initial step
toward the understanding of the complex chiral phenomenon seen experimentally at a
molecular level.
Figure 1. Integrated coverages and enantioselectivity
for the system PO/NEA/Pt(111).
91
P2
Results
Two models are proposed, and were tested.
Model 1: A square lattice was considered. A) A site surrounded by up to two adsorbed NEAs
among near-neighbor sites becomes selective and strong for (S)-PO adsorption; b) a site
surrounded by four near-neighbor NEAs becomes selective and strong for I-PO adsorption; c) a
th
site surrounded by 2 or more NEAs up to 4 order neighbors, which is not a selective site, is
forbidden for PO (R or S) adsorption. The results predicted by this model are shown in Figure 2.
As it can be seen, integrated coverages and selectivity are only very roughly reproduced.
Model 2: the surface is considered as an effective lattice composed of intertwined two square
sub-lattices with 3 types of sites: sites A (intersections of two lines in the first sub-lattice), weak
sites for PO; sites B (intersections of two lines in the second sub-lattice), strong sites for PO;
sites C (intersections of both sub-lattices), weak sites for PO.
The adsorption energies for PO on these sites (A, B and C) were fixed at W(B) = - 13.75
kcal/mol and W(A,C) = - 11.9 kcal/mol. Both PO and NEA were assumed to occupy a single site
on the effective lattice. At low coverage NEA is adsorbed randomly on A sites. Once a
coverage of 25% is reached, when those sites are all full, NEA can then adsorb randomly on C
sites, maybe in a “tilted” state occupying less surface area, as also suggested in [1].
Figure 2. Predictions of Model 1.
Figure 3. Predictions of Model 2.
The second model is based on the following rules:
Rule 1. If a PO is adsorbed at a site surrounded by 3 or more next-near-neighboring NEAs, then
rd
two near-neighbor sites (chosen at random) and all next-near and 3 -order neighbor empty
sites become enatioselective for (S)-PO. In addition, the PO adsorbed on that site becomes
strongly bounded to the surface.
th
Rule 2. If a site is surrounded by 2 adsorbed NEAs up to 4 -order neighbors, then it is forbidden
for PO adsorption.
Rule 3. If a site is surrounded by 5 or more near and next-near neighbor NEAs, then it is
forbidden for PO adsorption.
Predictions of this model, shown in Figure 3, reproduce the of the experimental system.
Conclusions
Model 1 is very simple and can be physically rationalized, but only reproduce experimental data
crudely. Model 2, on the other hand, reproduces well the experimental behavior, but its rules are
difficult to be rationalized. Consequently, the present work represents a very first step toward
the understanding of this chiral system at a molecular level, and may help to develop a better
model where the advantages of Model 1 and Model 2 could be combined.
References
Lee, Z. Ma, S. Kaneko and F. Zaera, JACS 130 (2008) 14597.
92
P3
Argine-Based surfactants: mixtures with 1,2 Dipalmitoyl-SN-glycero-3-phosphate
monosodium salt
1
1
2
1
2
Neus Lozano , Aurora Pinazo , Camillo La Mesa , Lourdes Perez , Patrizia Andreozzi ,
1
and Ramon Pons .
1
Departament de Tecnologia Química i de Tensioactius, Institut de Química Avançada de
Catalunya, Jordi Girona 18-26, 08034 Barcelona, Espanya
2
Dipartimento di Chimica, Università degli Studi “La Sapienza”, Piazzale Aldo Moro 5, I-00185
Rome, Italy
In search for new antimicrobial compounds to be used in food, pharmaceutical, and cosmetic
applications, a novel class of cationic arginine glyceride conjugates was developed. Preliminary
results on their physicochemical and biological properties showed that such novel compounds
combine the advantages of glycerides and lipoamino acids [1-4]. The chemical structures are
show in Figure 1.
O
8
HN
O
H
O
10
H
N
HO
NH2
NH2
O
Cl12
12
O
O
O
O
OH
P O
O
8
O
HN
O
O
O
H
NH2
NH Cl
2
O
10
H
N
H
N
Na
O
O
H
140RAc
O
DPPA
8
HN
O
O
LAM
O
O
O
10
NH2
NH Cl
O
O
O
O
HN
O
H
O
H
N
NH2
NH2 Cl
2
1414RAc
1212RAc
Figure1. Chemical structures of the cationic and anionic amphiphiles, Nα –lauroylarginine methyl ester hydrochloride
(LAM), 1,2 myristoyl-rac-glycero-3-O(Nα-acetyl-L-arginine) hydrochloride (1414Rac), 1,2 lauroyl-rac-glycero-3-O(Nαacetyl-L-arginine) hydrochloride (1212Rac), 1 myristoyl-rac-glycero-3-O(Nα-acetyl-L-arginine) hydrochloride (140Rac),
1,2-dipalmitoyl-sn-glycero-3-phosphate monosodium salt (DPPA).
At present renewed interest has been shown for amphiphilic systems containing both cationic
and anionic surfactants. These studies involve both theoretical and practical aspects. With the
purpose of deepening on the fundamental properties of new surfactants as well as the possible
application of these as formulated products this communication reports on the formulation of
novel cationic monoacyl and diacyl glycerol arginine–based surfactants with an anionic diacyl
phospholipid, 1,2-dipalmitoyl-sn-glycero-3-phosphate monosodium salt (DPPA), being part of
the rich family of pseudo triple-chain and pseudo-tetra-chain catanionic mixtures respectively [ ,
]. Vesicle size and ζ-potencial was measured at several mixing ratios. Additional information on
counterion binding, vesicle size, and integrity was obtained from ion selective electrode, SAXS
and Cryo-TEM measurements.
References
[1] Pérez L., Pinazo A., Vinardell M.P., Clápes P., Angelet M., Infante M.R., New J. Chem. 26, 1221 (2002).
[2] Morán M.C., Infante M.R., Clápes P., J. Chem. Soc. Perkin Trans. 1, 1124 (2002)
[3] Pérez L., Infante M.R., Angelet M., Clápes P., Pinazo A., Prog. Colloid Polym. Sci. 123, 210 (2004).
[4] Infante M.R., Pinazo A., iusep J., Colloids Surf. A, 123, 49 (1997).
[5] Marques E., Brito R., Wang Y., Silva B., J. Colloid Interface Sci., 294, 240 (2006).
[6] Karukstis K., Zieleniuk C.A., Fox M.J., Langmuir 19, 10054 (2003).
93
P3
94
P4
Lysine-based cationic surfactants: synthesis and study of the effect of the polar group
on their biological properties
1
1
2
2
1
1
Pérez, L. , Pinazo, A. , Vinardell, Mª.P ., Mitjans, M. , Infante, M.R. , Ribosa, I. , García,
1
3
1
M.T. , Manresa, A. and Colomer, A.
1
Departamento de Tecnología de Tensioactivos, IQAC/CSIC. C/Jordi Girona 18-26, 08034
Barcelona España.
2
Laboratori de Fisiología Facultat de Farmacia, UB. Av. Joan XXIII, 08028 Barcelona, España.
3
Laboratori de Microbiología, Facultat de Farmacia, UB. Av. Joan XXIII, 08028 Barcelona,
España.
Surfactants are surface active compounds that can adversely affect the environment. At present
the main driving force behind the development of novel surfactants and emulsifiers is the search
for environmentally friendly products. Due that, preparation of surfactants which mimic the
structure of natural compounds such as lipoaminoacids is currently increasing because of their
1,2,3,4
unique physicochemical and biological properties
. We report on the synthesis, biological
and physico-chemical properties of five different novel lysine-based surfactants. All of them
have dodecyl fatty chains, two have a monocatenary structure and three have a gemini
structure (See Figure 1). The synthesis is a classical amino-acid condensation. The surfactant
behaviour has been characterized by measuring the critical micelar concentration (CMC). CMC
values of monocatenary surfactants are similar to those of commercial cationic surfactants.
Concerning gemini surfactants CMCs are two orders of magnitude smaller than those of
monocatenaries surfactants. We have studied a number of biological properties. The hemolytic
activity of monocatenary compounds is smaller than that of their gemini counterparts. Both
monocatenary and gemini compounds are active against Gram-positive bacteria but not
noticeable activity has been observed when bacteria are Gram-negative. After 28 days, the
5
compounds biodegradation ratio amounts to 60% thus they fall within the category of readily
biodegradable surfactants.
H
N
10
COOMe
O
*
COOMe
O
H
N
10
NH3 Cl
N
H
NH3Cl
N
H
*
O
O
NH
NH
H2N Cl
NH2
H2N Cl
Nα-Lauroyl-Argine-Nα-Lysine (NαLANαK)
NH2
Nα-Lauroyl-Arginine-Nε-Lysine (NClαLANεK)H
H
N
+H3N Cl
+H3N
NH3+ Cl
H
N
N
6
O
O
O
H
N
H
N
NH
*
HN
O
O
+ Cl-
H
N
H
N
4
3
NH3+ Cl
O
*
10
10
6
O
O
O
10
NH
HN
NH
HN
O
O
10
10
+H 3N
NH3
Cl
+
*
Cl
1,6-hexandiamine-bis(Nα-Lauroyl-Lysine) (C6(NαLK)2)
O
*
10
*
1,6-hexandiamine-bis(Nε-Lauroyl-Lysine) (C6(NεLK)2)
Spermidine-bis(Nε-Lauroyl-Lysine) (C7NH(NεLK)2)
Figure 1. Synthetic lysine-based surfactants structure.
References
1. Pinazo, A., Wen, X., Pérez, L., Infante, M.R., Franses, E., “Langmuir”, 1999, 15, 3134-3142.
2. Pérez, L., Pinazo, A., García, M.T., Angelet, M., Lozano, M., Vinardell, P., Mitjans, M., Pons, R., Manresa, A., Infante,
M.R., “Eu. J. of Med. Chem.”, 2009, 1-9.
3. Pérez, L., Pinazo, A., Vinardell, P., Clapés, P., Angelet, M., Infante, M.R., “New. J. Chem.”, 2002, 26, 1221-1227.
4. Infante, M.R., Molinero, J. Erra, P., Julia, R., García J.J., “Fette Seifen Anstrichmittel”, 1983, 87(8), 309-313.
5. OECD Chemical group Ready biodegradability. Modified Screening test Method 301D, OECD revised guidelines for
ready biodegradability, OECD Paris, France, 1993].
95
P4
96
P5
Mono Acyl Lysine based surfactants: self-aggregation
Ramon Pons, Lourdes Pérez, Marina Lozano, M. Rosa Infante, Aurora Pinazo
Departament de Tecnologia Química i de Tensioactius, IQAC-CSIC, Jordi Girona, 18-26,
08034, Barcelona, Spain, [email protected]
Self-aggregation and surface properties of new acyl lysine based surfactants have been studied
as a function of hydrophobic chain length. Their general structure is presented in the figure.
These surfactants are biodegradable, biocompatible and present some antimicrobial activity.
The critical micellar concentration values are close to the expected for ionic surfactants with the
same chain length. The aggregates were characterised by NMR difussometry and the results
suggest notable anisometry as the chain length is increased. At higher concentration gel and
liquid crystalline phases have been identified by optical microscopy and SAXS. Lamellar and
cubic phases are present at high concentration.
O
+ H 3N
C l-
O
O
N
H
n
Nε-Lysine methyl ester surfactants
97
P5
98
P6
Gold supported on ceria doped by Me3+ (Me=Al and Sm) for
water gas shift: influence of dopant and preparation method
a
a
a
b
b
Ivanov , R. Nedyalkova , L. Ilieva , J. W. Sobczak , W. Lisowski , D. Andreeva
a
a
Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
Institute of Physical Chemistry, PAS, Kasprzaka 44/52, 01-224 Warsaw, Poland
b
Introduction
Gold catalysts based on ceria are very promising for various applications, among them one very
important is the production of pure hydrogen via water gas shift (WGS) reaction. Metal/ceria
catalysts are several orders of magnitude more active than metal/alumina or other oxide
supports for a number of redox reactions. Metal-modified ceria has a higher oxygen capacity
and enhanced reducibility than pure ceria. The addition of metal dopants to CeO2 with valences
lower than (4+) leads to the formation of oxygen vacancies in ceria, this should increased the
oxidation activity.
In this study we present the comparable results obtained for gold catalysts based on both ceria
undoped and ceria doped by Al and Sm and prepared by two different methods. The influence
of dopants’ nature and preparation techniques will be discussed.
Experimental
The supports were prepared by 2 different methods: by co-precipitation (CP) and by
mechanochemical activation (MA). The amount of the dopant was 10 wt.%. Gold was
introduced by deposition-precipitation method. The catalysts were tested in WGS reaction, the
catalytic activity was expressed as CO conversion. The samples were characterized by XRD,
HRTEM, Raman spectroscopy, XPS and TPR.
Results
The experimentally determined values of the SBET, lattice parameters of ceria and average
size of gold and ceria particles are presented in Table 1. In Figure 1 are presented the WGS
activities of the catalysts, compared to undoped gold supported on ceria.
100
Table 1. BET surface area, lattice parameters of ceria and average
size of gold and ceria particles
SBET
2 mg
1
AuCe
AuCeAlCP
AuCeAlMA
AuCeSmCP
AuCeSmMA
108
103
105
84
76
Average
size of
gold
nm
2.0
3.1
2.9
2.6
2.4
Lattice
parameter
1
of ceria
a (Å)
5.422
5.409
5.419
5.421
5.424
Average
size of
ceria
nm
8.0
4.2
9.6
7.1
8.5
80
CO conversion, %
Samples
90
70
60
50
AuCe
AuCeSmCP
AuCeSmMA
AuCeAlCP
AuCeAlMA
equilibrium
40
30
20
10
0
100
150
200
250
300
350
o
Temperature, C
Figure 1. Temperature dependence of CO
conversion of the studied catalysts
1
Lattice parameter of CeO2 = 5.412 Å
The MA catalysts exhibited higher activity than the CP catalysts and undoped ceria (AuCe). A
significant difference in the catalytic activity has been observed for CP catalysts doped by Al
and Sm. The CP catalyst modified by Sm was highly active, much more than Al doped CP
catalyst, and its WGS activity even increased after a long period of operation and reactivation in
air at 200 oC. There is a big difference between the catalysts CP and MA modified by Al. For
the corresponding samples doped by Sm this difference is smaller and after reactivation even
negligible. The Raman spectroscopy data showed also a significant difference between Al
doped CP and MA catalysts, while for the Sm doped samples this difference was insignificant.
99
P6
One possible explanation is, that in Sm doped catalyst the oxygen vacancies are located
around Sm. Ceria seems to be quite well ordered and its re-oxidation during catalytic operation
is enhanced. The XPS analysis of the fresh catalysts revealed an additional Au 4f XPS state at
higher BE, which we assigned to positively charged gold species. The contribution of such
species seems to be relatively higher for Sm doped catalyst than for corresponding catalyst
modified by Al. After catalytic operation only metallic Au was registered in all samples. The
hydrogen consumption, registered by TPR measurements, both of fresh and re-oxidized
samples showed higher oxygen capacity as compared to the non-doped ceria. There was no
distinct correlation between reducibility and WGS activity. The addition of the Sm and Al dopant
to ceria increases the stability of gold/ceria catalysts.
Conclusions
3+
Gold catalysts supported on ceria doped by Me were synthesized. Higher WGS activity was
found for the catalysts based on doped by Sm ceria in comparison to the catalysts, doped by
alumina. Generally the catalysts prepared by mechanochemical activation exhibit higher activity
than those prepared by co-precipitation, but the differences between WGS activities for Sm
doped samples are much smaller than that in the case of ceria-alumina catalysts. There are no
big differences in the gold particle size (2-3 nm) for the samples prepared by the two methods.
There is a big difference in the behaviour of the catalysts by the Raman spectroscopy data. In
the Sm doped catalysts a larger number of oxygen vacancies for the MA samples than for the
corresponding CP ones was observed. Most probably the oxygen vacancies are adjusted
around dopant and the ceria structure seems to be better ordered than in the case of alumina
doped ceria. There is no distinct correlation between reducibility and WGS activity. The surface
concentration of partially positively charged gold particles in fresh Sm doped samples,
registered by XPS, is higher than that of the samples doped by Al, but after catalytic operation
only metallic gold is observable. This is in agreement with the model of active sites of gold/ceria
catalysts for WGS reaction [1].
Acknowledgements
This work is supported by Bulgarian National Fund, Ministry of Sciences and Education, project
TK-X-1709.
References
[1] D. Andreeva et al., Topics in Catal., 44 (2007)173.
100
P7
Redox activity of gold-molybdena catalysts: influence of the preparation method
Petya Petrova*, Lyuba Ilieva, Donka Andreeva
Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria,
*
[email protected]
Introduction
The detoxification of hydrocarbons pollutants is one of the global environmental problems.
Considerable efforts have been made to design highly efficient catalysts for complete oxidation
of hydrocarbons. The interesting properties of ceria as a support for the noble metals catalysts
are well known mainly to concern its function as oxygen buffer. The synthesis of nanosized
ceria is an important factor for the preparation of highly active gold supported catalysts. The
addition of alumina to ceria increases the oxygen vacancies concentration, respectively oxygen
capacity and redox activity of this type of catalysts. We have also studied the effect of the
introduction of vanadia and molybdena as promoters to gold catalysts on the properties and
catalytic activity in complete benzene oxidation (CBO) [1-4].
The accent in this study is on the influence of the preparation method on the structure,
properties and reduction activity of gold-molybdena catalysts supported on ceria-alumina.
Nonpromoted and promoted by molybdena gold catalysts in the reaction of CBO are studied.
The role of oxygen vacancies concerning the redox properties and catalytic activity is also the
object of the discussion.
Experimental
The applied supports were prepared by two different methods: by coprecipitation (CP) or by
mechanochemical activation (MA). Amount of alumina was 10 or 20 wt% (signed as cipher after
Al). 3 wt% of gold was introduced by deposition-precipitation technique. Molybdena was
introduced by impregnation from a solution of (NH4)6Mo7O24. The catalysts were characterized
by XRD, Raman spectroscopy, XPS and TPR. The activity of the catalysts was determined in
CBO.
The catalytic behaviour of the samples is quite different depending on the preparation method
applied. The gold catalysts promoted by molybdena exhibit higher activity in comparison to the
corresponding nonpromoted ones in the low temperature (LT) interval. At higher temperatures
the opposite behaviour is observed. Depending on the alumina content, the temperature of the
cross-point of the two activity curves is different. This temperature is higher for the sample with
higher alumina content. The catalysts containing only molybdena showed negligible activities at
the studied temperatures. In Fig. 1 are compared the catalytic activities of the Au-Mo samples,
prepared by the both applied preparation techniques for the samples containing 10 wt% of
alumina (A) and for the samples, containing 20 wt% of alumina (B). One can see that in the LT
region the MA catalysts are more active, while in the HT region the activities are almost equal, a
little higher being that of CP ones. The redox activity of the samples was commented on the
bases of TPR measurements of fresh samples as well as after their re-oxidation. The results
obtained by TPR as well as by Raman spectroscopy confirmed the predominant surface
modification of ceria in the case of MA preparation method while CP techniques caused oxygen
vacancies formation deeper in ceria structure. Interesting XPS results were obtained with AuMo spent catalysts – supplementary to metallic gold both Auδ+ and Auδ- were obtained after
3+
catalytic operation. The XPS results also supported the role of Ce in the formation of active
sites for the redox processes.
101
100 (A)
90
80
70
60
50
40
30
AuMoCeAl10CP
20
AuMoCeAl10MA
10
0
140 160 180 200 220 240 260 280 300
0
Temperature, C
Conversion, %
Conversion, %
P7
100 (B)
90
80
70
60
50
40
30
AuMoCeAl20CP
20
AuMoCeAl20MA
10
0
140 160 180 200 220 240 260 280 300
0
Temperature, C
Figure 1. Temperature dependence of the CBO conversion over gold-molybdena catalysts: (A) containing 10 wt%
alumina and (B) containing 20 wt% alumina.
It was supposed that depending on the reaction temperature as well as on the method of
catalysts’ preparation, two factors are of great importance for the high redox activity – lattice
oxygen mobility and the enhanced electron transfer with the participation of nanosized gold
3+
particles and surface oxygen vacancies in close contact with them and Ce . The both factors
are connected to the oxygen vacancies formation caused by the addition of gold and alumina as
well as to the average size of gold and ceria.
Conclusions
The study of CBO activity over these complex catalytic systems manifested that the different
factors should be of crucial importance. In the LT region the effect of the electron transfer with
the participation of nano gold particles is prevailing and this is in agreement with significantly
higher activity of Au-Mo samples MA. In the HT region obviously the predominant role plays the
oxygen mobility, related to the oxygen vacancies in ceria structure.
Acknowledgements
This work was supported by the National Scientific Fund of Bulgaria, project MY-X-1603.
References
[1]
D. Andreeva, T. Tabakova, L. Ilieva, A. Naydenov, D. Mehanjiev, M.V. Abrashev, Appl. Catal. A: Gen., 209
(2001) 291.
[2]
D. Andreeva, R. Nedyalkova, L. Ilieva, M. Abrashev, Appl. Catal. A: Gen. 246 (2003) 29.
[3] D. Andreeva, R. Nedyalkova, L. Ilieva, M. Abrashev, Appl. Catal. B: Envir. 52 (2004) 157.
[4] D. Andreeva, P. Petrova, J.W. Sobczak, L. Ilieva, M.V. Abrashev, Appl. Catal. B: Envir. 67 (2006) 237; 77 (2008)
364.
102
P8
FTIR accessibility studies of 2,6 DTBPy adsorption on FCC catalysts
1,2
2*
A.C. Psarras , E.F. Iliopoulou and A.A. Lappas
1
2
2
Dept. of Chemical Engineering, Aristotle University of Thessaloniki. CPERI/CERTH
6 km Harilaou-Thermi Road, P.O. Box 60361-Thermi, GR-57001 Thessaloniki, Greece.
[email protected]
th
Introduction-Objective
Due to energy saving policies the refineries today tend to upgrade more and more of heavier or
resid fractions into lighter, desirable distillates via catalytic cracking. Larger molecules in
fractions of increasing boiling point mainly account for the difficulties in processing heavy oils. In
this study we try to measure the acid sites of FCC catalysts that are accessible, when
processing cumbersome molecules such as those of residual petroleum fractions. Vibrational
spectroscopy of adsorbed probe molecules is a powerful tool for catalytic acidity assessment.
Artificially and commercially deactivated FCC catalysts were studied using pyridine adsorption
and FTIR analysis [1], a technique not usually applied on complete FCC catalysts. Pyridine is a
strong base and easily gives rise to the formation of H-bonded and pyridinium species with
weak and strong Brönsted acid sites, respectively, and to coordinated species on Lewis acid
sites. For the characterization of the accessible acid sites 2,6-Di-Tert-Butyl-Pyridine is
employed. This probe molecule does not adsorb on Lewis sites due to steric hindrance effects.
Thus, DTBPy is suitable only for the measurement of the “useful” Brönsted acid sites. A debate
exists for the characteristic band of DTBPY adsorption for quantification purposes. The bands at
-1
+
3370, 1616 and 1530 cm are reported as characteristics of the DTBPyH ion [2].The scope of
the present study is to investigate the suitable characteristic band of DTBPY adsorption as well
as the most appropriate adsorption temperature.
Experimental
Experimental apparatus and procedure for acidity measurement using Pyridine is described
elsewhere [1]. Initially, the same procedure was used for the DTBPY adsorption. Interpretation
of the results using the Beer-Lambert law was realized as suggested in the literature [2] due to
the lack of molar extinction coefficients for this probe molecule. Besides β-zeolite we also used
a mesoporous Al-MCM-41 reference sample to ensure that all sites are accessible to both
pyridine molecules. Two commercially (E-cat1 & E-cat2) and two artificially (D-cat1 & D-cat2)
deactivated FCC catalysts were the samples under study. The zeolitic components (Zeo1 &
Zeo2) of the FCC catalysts were also investigated.
All experiments were realized more than once for repeatability reasons. All three characteristic
bands were included in the study in order to select the most appropriate one. The percentage of the
-1
high accessible acid sites is presented in Table 1. The utilization of the band at 1530 cm presents
-1
acceptable results with the best repeatability for the FCC catalysts. The band at 3370 cm , not
present at the normal pyridine spectrum appears in the region of amines and is attributed to the
+
vibration of the N-H bond. Such a band is a consequence of the higher basicity of the DTBPy in a
+
way that the bond N-H is short enough to be similar to an amine. Thus, the contribution of the acid
sites to this band is strongly related to their strength and not all of them contribute to this band. The
-1
results of the zeolitic samples using the band at 3370 cm resemble the results using the band at
-1
1530 cm with a slightly better repeatability. This observation can be attributed to the fact that the
fresh zeolitic samples contain high acidity with great strength, supporting our assumption about the
-1
-1
3370 cm band. Thus, the band at 3370 cm can be utilized, when fresh zeolitic samples are under
research due to the great strength of their acid sites. However, when deactivated FCC catalysts are
-1
-1
under research, the band at 1530 cm should be taken into account. The band at 1530 cm is
attributed to the ring vibration of the pyridinium ion, thus all the acid sites contribute to this band
-1
independently of their strength. The band at 1616 cm indicates also the ring vibrations of the
pyridinium ion but it is considered less suitable, as the physisorbed molecules may also contribute to
it (same case with the normal pyridine adsorption). The coverage of bridged hydroxyls calculated by
-1
-1
integrating the negative bands at 3630 cm and 3540 cm on the Zeo1 sample is more than 91%
103
P8
and on Zeo2 is 88%. This indicates that the results when using Al-MCM-41 as the reference sample
-1
and the 1530 cm band are more realistic, although utilization of the β-zeolite as reference sample
gives a slightly better repeatability.
Table 1: Percentage of accessible Brönsted sites using all characteristic bands for all samples
-1
Sample
used as ref.
D-cat1
nd
D-cat1 (2 )
rd
D-cat1 (3 )
E-cat1
nd
E-cat1 (2 )
Zeo1
nd
Zeo1(2 )
rd
Zeo1(3 )
D-cat2
nd
D-cat2 (2 )
E-cat2
nd
E-cat2 (2 )
Zeo2
nd
Zeo2(2 )
rd
Zeo2(3 )
-1
-1
Band at 3370 cm
β-zeolite
Al-MCM-41
Band at 1616 cm
β-zeolite
Al-MCM-41
Band at 1530 cm
β-zeolite
Al-MCM-41
0.897
1.267
0.818
2.575
1.395
0.396
0.513
0.526
1.339
1.261
2.681
1.880
0.618
0.446
0.621
1.086
1.553
1.014
2.211
1.484
0.532
0.581
0.602
1.356
1.194
1.982
1.621
0.762
0.503
0.754
0.525
0.526
0.538
0.746
0.669
0.688
0.685
0.668
0.750
0.697
0.735
0.751
0.710
0.589
0.669
1.392
1.228
1.269
2.278
1.742
0.631
0.840
0.816
1.846
1.861
2.394
2.230
0.834
0.887
0.821
0.713
0.577
0.665
0.732
0.753
0.360
0.406
0.395
0.775
0.739
0.664
0.773
0.424
0.441
0.410
0.647
0.623
0.666
0.881
0.811
0.853
0.852
0.826
0.918
0.858
0.869
0.906
0.867
0.748
0.815
The temperature effect of the DTBPy adsorption was investigated on the zeolitic sample Zeo1.
o
o
Additional adsorption trials at 50, 100 and 200 C, (besides the standard 150 C), were realized.
-1
-1
This study was motivated by the appearance of double peaks at 1530 cm and 3370 cm when
o
+
the 150 C was applied. It was observed that the single peaks related to the DTBPyH ion is
o
present only at 50 C until equilibration. After the equilibrium is reached, a decrease is observed
-1
-1
at both bands with a simultaneous appearance of shoulders at 1540 cm and 3350 cm . These
shifted bands are present from the beginning of the adsorption when a higher temperature is
applied (≥100°C). This observation can be related to the reac tion of the DTBPy probably
towards a branched pyridine smaller than DTBPy and larger than pyridine. The bands are
reaching equilibrium at the elevated temperatures, suggesting that this transformation of DTBPy
is not complete and only affected by the temperature. This gives validity to our former results,
but the accessibility refers to less bulky molecules. The study at room temperature will possibly
provide more accurate results about the highly accessible Brönsted acid sites according to the
size of the DTBPy.
Conclusions
-1
The band at 1530 cm is more reliable for the quantification of accessible Brönsted sites on FCC
-1
catalysts when 2,6-DTBPy is used as a probe molecule, although the band at 3370 cm can be
utilized for pure fresh zeolitic samples due to their high and rather homogeneous acidity strength.
The mesoporous Al-MCM-41 gives more realistic results when used as a reference sample. The
temperature of adsorption is affecting the results by enhancing the reaction (probably
o
dealkylation) of DTBPy. The adsorption equilibrium validates the results at 150 C, but the
percentage of the really highly accessible Brönsted acid sites is revealed by the adsorption study
at room temperature.
References
[1] A.C. Psarras, E.F. Iliopoulou, K. Kostaras, A.A. Lappas and C. Pouwels, Micropor. Mesopor. Mater. 120 (2009) 141146
[2] A. Corma, V. Fornés, L. Forni, F. Márquez, J. Martinez-Triguero and D. Moscotti, J. Catal. 179 (1998) 451-458
104
P9
Supramolecular Assemblies in Association Colloids:
from dilute to concentrated regimes.
1
2,3
4
1
Patrizia Andreozzi, Adalberto Bonincontro, Luigi Coppola, Federica De Persiis,
1,3
1,3,*
1
4
Luciano Galantini, Camillo La Mesa,
Claudia Leggio, Isabella Nicotera,
1,3
4
4
3,5
Nicolae V. Pavel, Cesare Oliviero-Rossi, Giuseppe A. Ranieri, Gianfranco Risuleo,
1
4
6
Franco Tardani, Mohamed Youssry, and Fioretta Asaro,
1
Dept. Chemistry, Sapienza University, Rome, Italy;
Dept. Physics, Sapienza University, Rome, Italy;
3
Soft-INFM, Sapienza University, Rome, Italy;
4
Dept. Chemistry, Calabria University, Arcavacata di Rende (Cs), Italy;
5
Dept. Molecular Biology, Sapienza University, Rome, Italy.
6
Dept. Chemistry, Trieste University, Trieste, Italy.
*
[email protected]
2
In the last years attention was focused to experience the experimental conditions leading from
simple association colloids, i.e. surfactant-, or lipid-based, micelles and liquid crystalline phases,
to hierarchically more complex structures, such as vesicles, cubosomes, nanoplatelets and
nanorods. All such systems are relevant in biologically-oriented advanced technologies,
because of the strong similarities the aforementioned objects have with structures occurring in
vivo. That’s why strong efforts are oriented to use such items in biomedical application fields,
including protein and DNA transfection technologies. Experiments performed on dilute regimes
give strong evidence on the formation of vesicles and nanorods, whereas other in concentrated
systems allow preparing vesicle-based entities from lamellar structures ordered by shear or
application of mechanical stresses.
Vesicles and nanorods are stable for indefinitely long times and were characterized by many
different experimental methods, spanning from DLS to electrophoretic mobility, from SAXS to
TEM or SEM, and so forth. Such supramolecular organization modes are ascribed to the
combination of different effects, namely hydrophobic, electrostatic, hydrogen-bond, etc. The
resulting structures and stability are governed by a delicate balance of all such effects, which
are also responsible for the interactions with biomacromolecules (DNA or Proteins). Some
biochemically intended applications are briefly discussed.
As to concentrated regimes, it has been demonstrated that applied shear favors the formation of
transient vesicular, tubular or rod-like (spring roll) geometries, whose stability is essentially
governed by composition, the system rheology and working temperature. Such transient
structures were investigated and rationalized by combining rheological methods with
multinuclear NMR, Rheo-NMR, NMR Imaging and PFGSE-NMR methods. Efforts were made to
link the properties of structures observed in dilute with those occurring in concentrated regimes,
to determine what are the main forces responsible for the stability of such entities, and to
determine whether the resulting stabilization is of kinetic or thermodynamic origin.
References.
[1] C. Letizia, P. Andreozzi, A. Scipioni, C. La Mesa, A. Bonincontro, E. Spigone J. Phys. Chem. B, 2007, 111,
898-908.
[2] A. Bonincontro, C. La Mesa, C. Proietti, G. Risuleo Biomacromolecules, 2007, 8, 1824-1829.
[3] A. Bonincontro, M. Falivene, C. La Mesa, G. Risuleo, M. Ruiz-Pena Langmuir, 2008, 24, 1973-1978.
[4] M. Alvarez Alcalde, A. Jover, F. Meijide, L. Galantini, N.V. Pavel, A. Antelo, J. Vasquez Tato Langmuir, 2008,
24, 6060-6066.
[5] V.H. Soto Tellini, A. Jover, F. Meijide, J.V. Tato, L. Galantini, N.V. Pavel Adv. Mater., 2007, 19, 1752-1756.
[6] C. Moran, M.R. Infante, L. Perez, A. Pinazo, L. Coppola, M. Youssry, I. Nicotera Colloids Surf. A:
Physicochem. Eng. Aspects, 2008, 327, 111-121.
[7] M. Youssry, L. Coppola, E.F. Marques, I. Nicotera J. Colloid Interface Sci., 2008, 324, 192-198.
[8] M. Youssry, L. Coppola, I. Nicotera, C. Moran J. Colloid Interface Sci., 2008, 321, 459-467.
105
P9
106
P10
New V, Nb, Ta – FAU zeolites – texture and surface properties
a*
a
a
a
b
Maciej Trejda , Anna Wojtaszek , Anna Floch , Maria Ziolek , R. Wojcieszak , E. M.
b
Gaigneaux
a
A. Mickiewicz University, Faculty of Chemistry, Grunwaldzka 6, 60-780 Poznań, Poland
Université catholique de Louvain, Unité de Catalyse et Chimie des Matériaux Divisés, Croix du
Sud 2/17, 1348 Louvain-la-Neuve, Belgium
[email protected]
b
Introduction
In the last years many researchers focused on catalysts containing niobium, vanadium and
tantalum as an active species. For the preparation of such materials both, co-precipitation and
post-synthesis methods were applied. Moreover, different kinds of the supports were used,
among them oxides [1] and mesostructured oxides [1,2] were studied. However, there are only
few data concerning the incorporation of niobium into crystalline structure, e.g. into zeolite
framework. The same is true in the case of two other elements belonging to the group five of
periodic table, i.e. vanadium and tantalum. Exemplary, such an attempt was done by Kevan et
al., who substituted silicon atoms by niobium during the synthesis of MFI structured zeolites [3].
Tantalum was also introduced via co-precipitation method into the same zeolite structure, i.e.
MFI, by Ko et al. [4].The post-synthesis method was applied by Dzwigaj et al. for the
introduction of vanadium into BEA structure [5].
In our work we focused on the incorporation of niobium, vanadium and tantalum species into
faujasite framework, namely into Y zeolite. The structure and Si/Al ratio of Y type zeolite
significantly differ from those of MFI and BEA zeolites studied before. Therefore, we expected to
obtain zeolites characterised by new surface properties and catalytic activity. For the
incorporation of mentioned elements the co-precipitation method was applied.
Experimental
The preparation of G5 elements containing FAU zeolites based on the modified two-steps
procedure reported originally by Ginter et al. [6]. In the first stage the so-called seed gel was
prepared with the composition of: 10.67 Na2O : Al2O3 : 10 SiO2 : 180 H2O and left to age at the
room temperature for one day. In the second stage so-called feedstock gel was prepared with
the composition of 4.3 Na2O : Al2O3 : 10 SiO2 : 180 H2O. The metal source was added both to
the seed and feedstock gel. The assumed Si/T ratio (T – V, Nb or Ta) was 64. Afterwards, a part
of the seed gel was added to the feedstock gel and the mixture was stirred vigorously for at
least 20 minutes. After stirring the gel was put to a polypropylene bottle and heated in oven for 5
hours in 373 K. The final product was washed with distilled water. The last step of preparation
was drying in 383 K for 12 hours. The vanadium containing zeolite was also prepared without
the addition of this metal into seed gel.The zeolites prepared in this study were characterised
using XRD, XRF, XPS, ICP, FTIR, UV-vis techniques. The catalytic tests for acidity/basicity and
redox properties of the samples were performed (e.g. acetonylacetone cyclisation).
Vanadium zeolites
The XRD patterns of synthesized vanadium containing zeolits (Na-VY1 and Na-VY2) indicated
the faujasite structure. Any peaks related to extraframework vanadium oxide phase were
observed. The SEM images showed well defined crystal structure and similar morphology. The
addition of vanadium into seed gel was found to be important for metal incorporation into the
zeolite. Nevertheless, the Si/V ratio in the final material was 15 times less that the assumed
value even in the case when vanadium was added to the seed gel (Table 1, Na-VY2). The UVvis spectra pointed out that vanadium species incorporated via co-precipitation method into Y
5+
zeolite show the tetrahedral coordination of V , which is typical for elements inside the zeolie
framework. However, further estimation of vanadium state by XPS analysis was not possible
due to the low concentration of this element in the final sample. The significant role of vanadium
species on surface properties of the material was shown in acid-base test reaction, i.e.
acetonylacetone cyclisation. The Brønsted basicity observed for this sample was assigned to
OH groups connected to V5+ in the skeleton.
107
P10
Niobium zeolites
The XRD pattern of Na-NbY zeolite
showed the characteristic peaks for
zeolites
crystalline FAU structure indicating the
Zeolite Assumed Si/T in
Si/Al in
a0
successful synthesis of this kind of
Si/T
the final
the final parameter material. The extraframework niobium
sample
sample
oxide species were not found on the
material surface, suggesting the
Na-Y
2.53
24.78
presence of niobium in the zeolite
Na-VY1
64
1600
24.81
framework. Similar information was
Na-VY2
64
960
2.82
24.81
given by UV-vis spectra, which
Na-NbY
64
170
2.45
24.81
showed
only
the
tetrahedral
64
88
2.78
24.78
Na-TaY
coordinated niobium and no band
corresponding to Nb2O5. The assumed
Si/Nb ratio for Na-NbY differed from this in the final sample. The amount of introduced niobium
was 2.5 times less than the assumed value. However, the efficiency of niobium incorporation
was much higher than those observed for vanadium zeolites. The increase of baseline in the
o
XRD pattern between 2 theta ca. 20-40 suggested that a part of the obtained material is also
present in the amorphous form. This was confirmed by SEM images, which showed amorphous
phase also beside crystalline one. To examine the location and state of niobium species the
XPS spectra were recorded. It was found that all niobium exhibit oxidation state +5. Moreover,
the biding energy for niobium (3d5/2) was higher (207.9 eV) than that typical for niobium bulk
oxide (207.3 eV). The increase of the binding energy was attributed to the different surrounding
of niobium species, e.g. in the Si-O-Nb link. Such a link is formed when niobium is incorporated
into the zeolite framework.
Table 1. The Si/T ratio and a0 parameters of prepared
Tantalum zeolites
The synthesis of tantalum containing zeolite (Na-TaY) was also succeded as evidenced by XRD
pattern. Moreover, the prepared sample exhibited well defined crystals and morphology. Inspite
of high efficency of tantalum incorporation (Table 1), i.e. relatively high metal concentration, no
extraframework Ta2O5 phase was detected. The UV-vis spectrum of Na-TaY sample showed
very intens and symmetric band at ca. 221 nm, which is characteristic of tanatlum in tetrahedral
coordination. This spectrum was completely different from the other registered for the Y zeolite
with tanatalum oxide in the extraframework position (reference sample). It strongly suggested
the incorporation of tanatalum into the zeolite framework. Similary to niobium, the XPS spectra
indicated that all tantalum is present on oxidation state +5. Moreover, the binding energy
registered for tantalum, which was higher than that typical for bulk tantalum oxide, suggested
the incorporation of this element into zeolite structure.
Conclusions
Niobium, vanadium and tantalum containing Y zeolites were successfully synthesized. The
characterisation of these materials indicated that G5 elements are incorporated into the zeolite
framework. The efficiency of the group five elements incorporation into faujasite framework can
be given in the following order: Na-TaY > Na-NbY > Na-VY. The synthesised materials showed
the different surface properties, Na-TaY and Na-VY Brønsted basic whereas Na-NbY acidic
character.
Acknowledgements
Polish Ministry of Science and Higher Education (grant 118/COS/2007/03) and COST
D36/0006/06 are to be acknowledged for a partial support of this work.
References
[1] X. Gao, I.E. Wachs, M.S. Wong, J. Y. Ying, J. Catal., 203 (2001) 18-24.
[2] M. Ziolek, I. Nowak, Zeolites, 18 (1997) 356-360.
[3] L. Kevan, A.M. Prakash, J. Am. Chem. Soc., 120 (1998) 13148-13155.
[4] Y.S. Ko, W.S. Ahn, Microporous Mesoporous Mat., 30 (1999) 283-291.
[5] S. Dziwigaj, Current Opinion in Solid State and Materials Science, 7 (2003) 461-470.
[6] D.M. Ginter, A.T. Bell, C.J. Radke, in Synthesis of Microporous Materials, Vol. 1, Molecular Sieves, M. L. Occelli, H.
E. Robson (eds.), Van Nostrand Reinhold, New York, 1992, p 6.
108
P11
Lignin-based electrospun carbon microforms
1*
1
2
4
3
R. Ruiz-Rosas , J. Bedia , M. Lallave , A. Barrero , I.G. Loscertales ,
1
1
J. Rodríguez-Mirasol , T. Cordero .
1
Chemical Engineering Department, University of Malaga, 29071 Málaga (Spain)
2
YFLOW-Sistemas y Desarrollo S.L., PTA, 29050 Málaga (Spain)
3
Fluids Mechanics Department, University of Malaga, 29071 Málaga (Spain)
4
Fluids Mechanics Department, University of Sevilla, 41092 Sevilla (Spain)
Objectives
Electrospinning is a simple and versatile method for generating fibrilar and spherical structures
from a rich variety of materials. This technique requires the use of a high voltage electrostatic
field to charge the surface of a solution droplet and thus to induce the ejection of a liquid jet
through a spinneret. Carbon submicroforms have attracted enormous attention due to their
excellent mechanical, chemical and thermal properties. Lignin is one of the most abundant
polymers in nature and constitutes an underutilized by-product of the papermaking industry.
This work is aimed to the production of carbon spheres, tubes, hollow and filled fibers of
interesting surface properties through electrospinning of lignin-based solutions.
Results
Figure 1 shows SEM and TEM images from the microforms carbonized at 900ºC. Change
between spherical (Fig. 1.a) or fibrilar (Figures 1.b to 1.d) form is achieved modifying the feed
rate and viscosity of the lignin solution in the electrospraying process.
Hollow spheres or fibers (Figures 1.a to 1.c) can be prepared using an oil template, which is
inserted through the inner needle of a tri-axial syringe electrospinning configuration. Selecting
oils of different viscosity allows moulding the shape of the fibers. The green bean appearance of
the carbon fibers is conferred by droplets of low viscosity template oil inside them and can be
seen in the TEM image detail of Figure 1.b.
The use of higher viscosity oils conducted to formation of carbon tubes. It was confirmed by
transmission electron micrographs, which show tubes of diameters in the range of 1-2 microns
and shell widths from 200 to 600 nm, Figure 1.c and detail.
Filled carbon fibers of diameters around 400 nm were prepared by co-axial electrospinning. The
TEM on Figure 1.d shows similar carbon fibers with well dispersed platinum particles of sizes
around 10 nm, which were directly added to lignin solution as a platinic salt. This simple method
to prepare platinum supported carbon fibers points out the flexibility of this technique.
Table 1 presents the textural properties of the carbonized fibers. The high BET areas and the
lack of mesoporous structure demonstrates that these materials are mainly microporous. Similar
values of micropore volume measured by means of nitrogen and carbon dioxide indicates the
narrow character of this microporosity.
Table 1. Porous structural parameters of the carbon fibers.
Morphology
Bean-like Fibers
Filled Fibers
ABET
2
(m /g)
758
1195
N2
CO2
At
Vt
VDR
2
3
3
(m /g) (cm /g)
(cm /g)
10
0.355
0.368
21
0.523
0.443
109
P11
Figure 1. SEM and TEM images of carbonized a) hollow spheres (SEM bar: 2 µm), b) hollow greenbean-like fibers, c)
tubes (SEM bar: 1000 nm) and d) Filled fibers (SEM bar: 500 nm).
Table 2 presents the XPS and ultimate analysis for the lignin-based tubes. The stabilization
process increases the oxygen content of the tubes, which improve their glass transition
temperatures avoiding the fusion during the subsequent carbonization process. Carbonization
of the stabilized tubes produces an increase in the carbon content due to the removal of oxygen
surface groups. Similar trend is observed for the other fibrilar morphologies.
Table 2. Mass concentration for tubes at different preparation stages.
XPS
Sample
Lignin tubes
Stabilized tubes
Carbonized tubes
C (%)
72.5
65.9
96.2
O (%)
27.5
34.1
3.8
C (%)
69.2
58.8
96.0
Ultimate Analysis
H (%)
O (%)
5.9
3.6
1.0
24.9
37.6
3.0
Conclusions
Electrospinning is a suitable technique for obtain carbon materials of several forms from lignin.
The flexibility of the technique makes possible the tailoring of the material morphology just
modifying a few of the electrospinning variables, even allowing the preparation of catalysts
through the incorporation of metallic salts during the initial stage. Carbon submicroforms of
2
sizes well below the micron, with total surface areas of more than 1000 m /g and of different
quantities and types of oxygen superficial groups have been obtained using this method.
Acknowledgements
This work was supported by the Spanish Ministry of Education and Science under grants
NAN2004-09312-C03-03 and CTQ 2006/11322.
110
P12
2-propanol decomposition on carbon based acid and basic catalysts
*
J. Bedia , J.M. Rosas, D. Vera, J. Rodríguez-Mirasol, T. Cordero
Chemical Engineering Department, School of Industrial Engineering,
University of Málaga, Campus de El Ejido s/n, 29013 Málaga, Spain
[email protected]
Objective
The objective of this study is the preparation and characterization of carbon based catalysts
obtained by chemical activation of olive stone waste for the catalytic decomposition of 2propanol. The activation was carried out with different activating agents of acidic (H3PO4 and
H2SO4) and basic (Ca(OH)2 and Ba(OH)2) character.
Results
The carbon based catalysts were denoted with PAC, SAC, BaAC and CaAC when H3PO4,
H2SO4, Ca(OH)2 and Ba(OH)2 were used activating agents, respectively, followed by the
activation temperature in degrees Celsius. The porous structure of the carbons was
characterized by N2 adsorption-desorption at -196 ºC. All the carbons but the obtained by
activation with H3PO4 (PAC) show type I N2 isotherms (not shown) characteristic of microporous
materials. PAC carbon show a type IV isotherm characteristic of a microporous structure with a
significant contribution of the mesoporosity. The carbons obtained show apparent surface areas
2
2
between 68 m /g for the carbon obtained by activation with Ca(OH)2 to 580 m /g for the
obtained by activation with H3PO4.
The activity of the carbon based catalysts was analyzed for the catalytic conversion of 2propanol. Figure 1 represents the steady state conversion of 2-propanol on the different carbon
based catalysts in the absence of oxygen. The acidic carbons PAC-500, SAC-600 and SAC-900
show significantly higher steady state conversions than those corresponding to the basic
carbons BaAC-700 and CaAC-900. The highest conversions were obtained using PAC-500 as
catalyst. The activation of lignocellulosic residues with phosphoric acid has proven to yield acid
carbon catalysts in a single step with a high activity in the alcohol decomposition [1].
1
PAC-500
SAC-600
SAC-900
BaAC-700
CaAC-900
Conversion
0.8
0.6
0.4
0.2
0
100
200
300
400
500
Temperature (ºC)
600
700
Figure 1. Steady state conversion of 2-propanol on the different carbon based catalysts in the absence of oxygen (Po =
0.0185 atm, W/Fo = 0.0.073 g·s/µmol).
The conversion of 2-propanol has been related to the presence of both acid and basic sites on
the surface of catalysts. In the broad outline, 2-propanol dehydrates to propylene or diisopropyl
ether over acid catalysts and dehydrogenates to acetone over basic catalysts [2]. In absence of
oxygen acidic carbon based catalysts (PAC and SAC) yield only propylene as dehydration
product, while basic carbon catalysts (CaAC and BaAC) mainly dehydrogenate 2-propanol to
acetone although a significant amount of propylene is also obtained (Figure 2). In the presence
of oxygen (21%vol), the acidic carbons show higher conversion values and part of the 2propanol suffer oxidative dehydrogenation yielding acetone as well as propylene, although at
111
P12
high 2-propanol conversion values only propylene is obtained as can be seen in Figure 3, which
represents the 2-propanol steady state conversion on PAC-500 carbon based catalyst.
1
0.4
0.2
0.2
0
0
300
400
500
600
700
0.8
Conversion
Sacetone
Spropylene
0.6
0.4
0.6
0.4
0.2
0.2
0
0
100
150
200
250
300
Temperature (ºC)
Temperature (ºC)
Figure 2. Steady state 2-propanol conversion and
selectivities for BaAC-700 carbon in the absence of
oxygen (Po = 0.0185 atm, W/Fo = 0.0.073 g·s/µmol).
Figure 3. Steady state 2-propanol conversion and
selectivities for PAC-500 carbon in the presence of
oxygen (Po = 0.0185 atm, W/Fo = 0.0.073 g·s/µmol).
Conclusions
Acidic and basic carbon based catalysts were prepared by chemical activation of olive stone
waste. The activation was carried out with different activating agents of acidic (H3PO4 and
H2SO4) and basic (Ca(OH)2 and Ba(OH)2) character. In absence of oxygen acidic carbon based
catalysts dehydrate 2-propanol to propylene and basic carbon catalysts mainly dehydrogenate
2-propanol to acetone although propylene is also obtained. In the presence of oxygen, the
acidic carbons show higher conversion values and part of the 2-propanol suffer oxidative
dehydrogenation yielding acetone as well as propylene, although at high 2-propanol steady
state conversion values only propylene is obtained.
Acknowledgements
We gratefully acknowledge to the Spanish DGICYT, Projects PPQ2003-07160 and CTQ200611322. J.B. acknowledges the assistance of the Ministry of Science and Education of Spain for
the award of a FPI grant.
References
[1] J Bedia, J M Rosas, J Márquez, J Rodríguez-Mirasol, T Cordero. Carbon 47 (2009) 286-94.
[2] MA Aramendia, V Borau, C Jiménez, JM Marinas, A Porras, FJ Urbano. J Catal 161 (1996) 829–38.
112
Selectivity
0.4
0.6
Selectivity
Conversion
Spropylene
Sacetone
0.6
1
0.8
0.8
Conversion
0.8
Conversion
1
1
P13
Catalytic and non-catalytic carbonization of hemp: the carbonaceous product
*
M.J. Valero , A. Gallardo, J. Bedia, J. Rodríguez-Mirasol, T. Cordero
Department of Chemical Engineering, School of Industrial Engineering,
University of Málaga, 29071 Málaga, Spain
[email protected]
Objective
The study of new ways of biomass conversion into useful materials, such as carbon materials
with controllable micro and nanostrucutures has been an appealing topic in materials chemistry
because of their many important applications as adsorbents, filter materials, catalyst supports,
electrode materials, energy-storage materials and stationary phases in liquid chromatography.
Hemp is currently being used in the textile, paper and plastics industries, which generates a
significant amount of residue. The development of recycling processes of such residues and
research into new methods for obtaining high-value materials are generating great interest.
Hydrothermal carbonization (HTC) or hydropyrolysis is a convenient way to convert biomass at
moderate conditions into carbonaceous nanostructures and/or liquid oil.
The objective of this work is the analysis of the carbonaceous nanostructures and the liquid oil
obtained from the uncatalyzed and catalyzed hydrothermal carbonization of hemp residues at
different reaction conditions.
Results
The hydropyrolysis of hemp (canes and fibers) biomass was performed in a Teflon-lined
stainless steel autoclave at moderate conditions (temperature up to 250ºC). The catalysts used
were NaOH and FeCl3 at different concentrations. The effect of the catalyst, the reaction
temperature and the residence time was studied.
The hydropyrolysis of hemp results in carbonaceous nanoparticles, coexisting with some larger
structures and liquid mixtures containing mainly acetic acid with lower amounts of methanol, 2furaldehyde, guaiacol and acetone among other products. A significant increase of both
biomass conversion and liquid product yields were observed using FeCl3 as catalyst.
Figure 1 shows some of the carbonaceous structures obtained using hemp as raw material.
Suitable conditions of pH, reaction time and temperature were essential for the synthesis of
carbonaceous spheres. The HTC of hemp canes and fibres resulted in different amounts of
these carbon spheres. The presence of FeCl3 and the uncatalized HTC resulted in a massive
formation of carbonaceous microstructures, while the presence of an alkaline solution of NaOH
restrained their formation.
Hemp canes (HC) and solid products obtained by HTC of the HC with and without catalyst (WC)
were carbonized at 500 and 900 ºC under continuous N2 flow. The mass surface concentrations
of the carbonized samples, determined by XPS quantitative analysis, are reported in Table 1.
The main elements found on the surfaces of the carbonized samples were carbon, oxygen and
lower amounts of phosphorus, calcium and silicon, characteristic of biomass materials. Other
elements such as nitrogen, magnesium or chlorine were also detected, but at very low
concentrations. A significant amount of sodium and iron were observed on the surface of the
carbonized solid products from the catalytic process with NaOH and FeCl3, respectively. The
treatment at 900 ºC eliminated almost completely the sodium content from the surface by
volatilization. However, the iron content on the surface decreases only slightly with
carbonization at 900 ºC.
113
P13
Figure 1: SEM image of the solid product obtained from HTC at 250ºC of (a) hemp canes (bar length: 1 µm) and (b) of
hemp fibers (bar length: 2 µm).
Table 1. Mass surface concentration (%) determined by XPS quantitative analysis of the hemp canes and
HTC solid products carbonized at 500 and 900ºC.
500HC
500WC
500FeCl3
500NaOH
900HC
900WC
900FeCl3
900NaOH
C 1s
66.19
78.61
74.68
66.37
50.63
91.38
89.08
87.05
O 1s
30.37
15.41
13.60
16.88
20.45
5.12
5.99
8.94
N 1s
0.96
1.18
0.81
0.00
0.00
0.00
0.00
0.00
Na 1s
0.00
0.00
0.00
11.14
0.00
0.00
0.00
0.20
Fe 2p
0.00
0.00
4.42
0.00
0.00
0.00
3.31
0.00
P 2p
1.10
0.65
0.57
5.61
10.20
1.99
0.42
0.00
Ca 2p
0.85
2.76
2.10
0.00
15.32
0.97
0.00
3.81
Conclusions
HTC process is a promising method for the synthesis of interesting well-defined carbonaceous
micro and nanostructures using hemp biomass as carbon precursors. The influence of reaction
time, temperature and the use of catalysts on the carbonaceous nanostructures and/or liquid oil
produced during HTC of hemp residues have been studied.
Acknowledgements
This work was supported by the Spanish Ministry of Education and Science under grants
NAN2004-09312-C03-03 and CTQ 2006/11322.
114
P14
Surface chemistry modification of carbon supported chromium catalysts after NO
reduction by XPS analyses
J.M. Rosas, J. Rodríguez-Mirasol, T. Cordero
Chemical Engineering Department. School of Industrial Engineering, University of Málaga.
Campus de El Ejido, s/n, 29013 Málaga, Spain
Introduction
X-ray photoelectron spectroscopy (XPS) allows the analysis of the atomic surface composition
of a solid and also provides the oxidation state of their components. This technique can give us
surface information about both the modification of atomic surface composition after a reaction
and the reactive and products bound to the solid surface. In this sense, XPS can be helpful for
mechanistic studies of different reactions, used with other complementary techniques. This
method was used to study the nitric oxide reduction on carbon supported chromium catalyst
with different gas atmospheres.
Experimental
The catalyst, CAC-Cr, was obtained by pore-volume impregnation of a dried activated carbon
(prepared by chemical activation of citrus skin with phosphoric acid, CAC) with an aqueous
solution of Cr(NO3)3·9H2O, corresponding to 10 wt% of the most stable oxide (Cr2O3). After
drying, the active phase (Cr2O3) was obtained by heating at 400 ºC in a flow of nitrogen.
The reduction experiments were performed at atmospheric pressure and different temperatures
(300-600 ºC), in a fixed bed reactor with 4 mm of internal diameter, using 300 mg of sample (80
3
mg of catalyst, diluted with 220 mg of SiC). The total flow rate was 200 cm STP/min, for
different concentrations of NO ranging from 200 to 800 ppm of NO, 1% CO, 2000 ppm C3H6,
2000 ppm SO2 and 3% O2. X-ray photoelectron spectroscopy (XPS) analyses were obtained
using a 5700C model Physical Electronics apparatus with MgKα radiation (1253.6 eV).
CAC-Cr catalyst fresh and after NO reduction reactions was analyzed by XPS. Table 1 shows
the mass surface concentrations of the carbon-supported chromium catalyst before an after
reaction with 200 ppm NO and different gases, at temperatures between 300-600 ºC, except for
the reaction in the presence of oxygen that was carried out at 350 ºC. The results show an
increase of the surface nitrogen amounts after direct NO reduction and reduction in the
presence of CO, compared to that of the fresh catalyst, while a similar nitrogen content is
observed after the reaction NO-C3H6 .Figure 1 shows the XPS spectrum of N 1s for the catalyst
CAC-Cr at the same previous conditions. The results evidence the formation of nitrogen surface
complexes with the reaction of NO, NO-CO and NO-SO2. The presence of oxygen produces the
formation of oxygen surface complexes that iusep the NO reduction to N2, avoiding the
formation of stably surface nitrogen complexes, as reported by Suzuki et al.[1]. Different authors
suggest the presence of pyridinic complexes at 398.7 eV, pyrrolic complexes at 400.2 eV and
quaternary nitrogen complexes with a positive formal charge at 401.4 eV.[2]. A higher
contribution of the peak obtained at lower binding energies is observed with the NO reaction,
associated to pyridinic complexes.
We have previously observed by transient kinetic experiments that the reducing agent must be
necessary adsorbed on the catalyst surface in order to reduce nitric oxide. A similar surface
nitrogen content of the carbon-supported chromium catalyst before an after NO-C3H6 reaction
suggests that a Eley-Rideal mechanism may be taken place. Specifically, for CO as reducing
agent, the formation of carbon-nitrogen complexes, as pyrrolic and pyridinic groups, during the
reduction of NO, indicates, preferentially, a Langmuir-Hinshelwood mechanism, where both NO
and CO must be adsorbed on the catalyst surface.
115
P14
Table 1. Mass surface concentration (%) determined by XPS quantitative analysis of fresh and used and
chromium catalysts.
C 1 s ( %) O 1 s ( % ) C r 2 p ( % ) N 1 s ( %) P 2 p ( %) S 2 p ( %)
C AC - C r
77.13
15.06
3.17
0.93
3.71
-
N O ( 3 0 0 - 6 0 0 ºC )
77.06
15.17
3.05
1.60
3.12
-
N O +C O ( 3 0 0 - 6 0 0 º C )
68.16
23.44
3.05
2.60
2.75
-
N O +C O + O 2 ( 3 5 0 ºC )
62.14
27.46
3.84
0.77
5.79
-
N O +C 3 H 6 ( 3 0 0 - 5 0 0 ºC )
78.77
14.23
3.26
0.73
3.02
-
N O +C 3 H 6 +O 2 ( 3 5 0 º C )
72.07
18.88
3.39
1.39
4.27
-
N O + SO 2 ( 3 0 0 - 6 0 0 º C )
70.06
19.32
3.54
2.79
3.47
0.81
NO+SO2 (300-600 ºC)
N(E)/E
NO+CO (300-600 ºC)
NO (300-600 ºC)
NO+C3H6+O2 (350 ºC)
CAC-Cr
NO+C3H6 (300-500 ºC)
NO+CO+O2 (350 ºC)
405
404
403
402
401
400
399
Binding energy (eV)
398
397
396
395
Figure 1. XPS N1s spectra of fresh CAC-Cr and after reaction with 200 ppm NO and different gases at temperatures
between 300-600 ºC.
Conclusions
XPS analyses show an increase of the nitrogen content for both NO direct reduction and in the
presence of CO, as pyridinic and pyrrolic complexes. However, no formation of nitrogen
complexes is observed in the presence of propylene as reductant agent. In based of these
results, an Eley-Rideal mechanism can be taken place more probably, for NO reduction, where
propylene is adsorbed on the active sites. While, for CO as reducing agent, a LangmuirHinshelwood mechanism, where both NO and CO are adsorbed could be likely obtained.
Acknowledgements
The authors thank the Ministry of Education and Science of Spain for financial support (Project
CTQ2006/11322).
References
[1] Suzuki, T.; Kyotani, T.; Tomita, A. Ind. Eng. Chem. Res. 1994, 33, 2840-2845.
[2] Pels, J.R.; Kapteijn, F.; Moulijn, J.A.; Zhu, Q.; Thomas, J.M. Carbon 1995, 33, 1641-1653
116
P15
CH4 combustion activity of Pd catalysts supported on TiO2 incorporated mesoporous
SiO2 (SBA-15 and HMS)
a*
a
a
G. Pantaleo , G. Di Carlo , L. F. Liotta , A. M. Venezia
a
a
Istituto dei Materiali Nanostruturati (ISMN-CNR) via Ugo La Malfa, 153, Palermo, I-90146,
*
[email protected]
Objective
Pd-based catalysts for methane oxidation at low temperatures suffer from deactivation due to
particle sintering and exposure to sulfur compounds. Recent studies had shown a remarkable
effect of the mesoporous HMS silica, limiting the PdO agglomeration, lessening the SO2
poisoning and allowing easy reactivation of the catalyst [1]. When amorphous composite sol-gel
oxides, TiO2-SiO2, with a small amount of titania and with high surface area were used as
supports, an additional increase of the catalyst oxidation activity and also an enhancement of
the sulfur tolerance was obtained [2]. Aiming to further improve the catalytic performance of the
PdO catalysts the use as supports of mesoporous incorporating titania, is here explored.
Results
Mesoporous silicas (SBA-15 and HMS) containing 5 and 10 wt% of TiO2 were prepared and
characterized by XPS, XRD, BET and the acidity of the supports evaluated on the basis of
ammonia TPD. The 1 wt% Pd was supported by incipient wet impregnation from aqueous
solution of Pd(NO3)2 (Aldrich). The methane oxidation activity was measured in lean conditions
−1 −1
at WHSV= 60 000 ml g h in absence and in the presence of 10 vol. ppm SO2. Stability tests
were performed after 16 h at 600°C under the reacti ng mixture. Mesoporous silicas enhanced
the palladium activity as compared to amorphous silica, to an extent which depended on the
particular mesoporous structure. Moreover, as shown in Fig.1, for the SBA-15 supported
catalysts, the presence of TiO2 improved the sulfur tolerance and most importantly it favored the
regeneration of the catalyst in the following SO2-free run. The opposite effect was observed on
the HMS samples, see Table 1. In fact, by increasing the Ti loading in the Pd-HMS catalysts, an
increase of the T50 (temperature of 50% CH4 conversion) values was observed in both cycles,
with and without SO2.
100
CH4 conversion (%)
80
60
full symbol =1st run with SO2
open symbol =2nd run SO2 -free
40
20
0
200
300
400
500
600
Temperature (°C)
Figure. 1. Methane conversion for PdSBA15 (black), Pd/Ti5SBA (red) and Pd/Ti10SBA (green).
117
P15
Table 1. T50 CH4 conversion for PdSBA15, PdHMS, PdTiSBA15 and PdTiHMS samples
Sample
PdSBA15P
PdTi5SBA
PdTi10SBA
PdHMS
PdTi5HMS
PdTi10HMS
I cycle with
SO2 (°C)
405
383
334
382
407
422
II cycle (°C)
SO2 free run
395
325
292
359
375
383
Conclusions
The presence of TiO2 improves the activity and the regeneration of the catalyst in the SO2-free
run in case of SBA-15 samples whereas exactly the opposite trend was observed on HMS
samples. The catalytic behaviour could be explained in terms of structural properties and
acidity.
Acknowledgements
European Community through (NoE) IDECAT and COST D36 action is acknowledged for
financial support.
References
[1] A. M. Venezia, R. Murania, G. Pantaleo, G. Deganello, J. Catal. 251 (2007) 94.
[2] A. M. Venezia, G. Di Carlo, G. Pantaleo, L. F. Liotta, G. Melaet, N. Kruse, Appl. Catal B. 88 (2008) 430
118
P16
Ketonization of aliphatic acids over zinc chromite catalyst
1
1*
1
1
Vladislavs Stonkus , Kristine Edolfa , Ludmila Leite , Mendel Fleisher , Andulis
1
2
Shmidlers , Lyuba Ilieva
1
Latvian Institute of Organic Synthesis, 21 Aizkraukles Str., Riga LV-1006, Latvia
*
[email protected]
2
Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
Objective
It is known that acetone and other ketones as highly reactive compounds find wide application
in synthesis of polymers, pesticides, and pharmaceuticals, as well as in utilization as solvents
and extractives. We have established earlier, that at temperatures below 400ºC the main
products of aliphatic aldehydes and alcohols transformation over zink chromite catalyst are
ketones [1, 2]. The aim of the present work is to gain deeper insight into the behavior of Zn-Cr
oxide catalyst in the conversion of aliphatic acids.
Results
Zn-Cr oxide catalyst was prepared by coprecipitation from salt solution. X-ray diffraction
analysis established that by mixing of saturated ZnSO4 and (NH4)2CrO4 solutions and addition
of equimolar amount of NH4OH, zinc ammonium oxychromate ZnOHNH4CrO4 is precipitated.
The dried precipitate upon heating at 290-300ºC formed the catalyst possessing disordered zinc
chromite spinel structure, with equimolar quantity of ZnO being dissolved in it. The TPR method
+6
3+
showed that Cr is completely reduced to Cr during calcination of catalyst precursor by NH3,
evolved in this process. It is supposed that catalyst deactivation above 400ºC is connected with
ordering of the spinel structure as a result of thermal processing. BET surface area of the
obtained catalyst is 57 m2/g.
The catalysts have been tested for ketonization of acetic, propionic and butyric acids. The
effects of temperature, catalyst loading, and the molar ratio of acid:water were investigated. The
results of catalytic tests performed in the presence of water in molar ratio acid:water=1:2) in the
о
temperature range 300-400 С are represented in Table 1. The acids conversion into ketones
о
was the highest (87-96%) at 325-350 C.
Table 1. Conversion of aliphatic carboxylic acids to ketones over zinc chromite catalyst in accordance with
temperature.
Acetic acid
Reaction
T, °C
Propionic acid
Conversion,
%
Selectivity
to acetone,
%
Conversion,
%
300
95.1
93.3
325
98.8
96.1
350
100.0
375
100.0
400
100.0
Butyric acid
Selectivity, %
Conversion,
%
Acetone
19.8
0.0
Methylpropylketone
3.4
40.2
0.0
2.6
92.3
93.1
91.5
0.1
4.2
90.3
84.9
99.0
2.3
17.0
67.8
62.1
99.0
7.8
21.8
25.6
48.4
Methylethylketone
0.6
Diethylketone
89.7
90.2
0.7
95.0
93.9
99.8
2.7
90.3
100.0
6.5
84.2
100.0
12.3
Selectivity, %
Dipropylketone
87.8
The comparison of ketonization processes of butyric acid, butanol and butanal showed that the
selectivity to ketone decreased in the order: acid>aldehyde>alcohol (Table 2).
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P16
Table 2. Comparison of ketonization proceses of butyric acid, butanol and butanal
Reaction
T, °C
Acid
300
325
350
375
400
19.8
40.2
91.5
99.0
99.0
Conversion,
%
Alcohol
Aldehyde
22.8
54.6
86.2
99.5
100.0
39.6
68.5
97.5
100.0
100.0
Selectivity to dipropylketone
formation, %
Acid
Alcohol
Aldehyde
87.8
92.3
90.3
67.8
25.6
19.0
49.4
72.2
75.6
22.2
25.8
53.7
80.4
67.7
23.0
The gaseous products of acetic acid conversion are H2, CH4, CO, of propionic acid – H2, CH4,
CO, C2H4, C2H6, of butyric acid – H2, CH4, CO, C3H6, C3H8.
On the basis of above data, it was possible to conclude that transformations of acetic acid over
Zn chromite catalyst proceedes according to the general equation 1 and two negligible
reactions: decarboxylation (2) and oxidation (3):
Ketonization 2CH3COOH→CH3COCH3+CO2+H2O (1)
Decarboxylation CH3COOH→CH4+CO2
(2)
Oxidation CH3COOH+2H2O→2CO2+4H2
(3)
Similar reactions are observed in the case of propionic and butyric acid too. We are proposing
that the ketonization of aliphatic aldehydes, alcohols and acids on Zn-Cr-O catalyst proceeds
according to dissociative – associative reaction mechanism, i.e., the reactants dissociate on the
surface of catalyst to fragments, and these fragments combine together by association to form
the reaction products.
The ketonization mechanism of acetic acid was investigated by semiempirical quantum
chemical AM1 method using the cluster approach. It is found that the adjacent acid-base pair of
the catalytic sites provokes dissociative adsorption of the acetic acid molecules resulting in the
formation of surface carboxylate species. Adsorption process proceeds spontaneously. After
blocking the acid-base pairs of catalyst, the new portions of acetic acid molecules interact with
active species in the gas phase, converting into acyl cations. The methyl group of adsorbed
carboxylate species is attacked by the acyl cation resulting in the bimolecular electrophilic
substitution reaction and formation of an acetone molecule and a carbon dioxide one.
Conclusions
The ketonization of aliphatic acids over a zinc chromite catalyst gives symmetric ketones at 325350ºC with high selectivity (90-96%). Selectivity to symmetric ketones in the case of conversion
of acid is higher than that of the corresponding alcohol aldehyde. At 375-400ºC, the destruction
of molecules significantly rises. It is concluded that ketonization of aliphatic acids over chromite
type catalysts is a perspective method for ketones production.
References
1. V. Stonkus, Zh.Yuskovets, M. Shymanska, Zh. Obshch. Khim., 64 (2) (1994) 295.
2. V. Stonkus, Zh. Yuskovets, M. Shymanska, Latv. Khim. Zh., N4 (1993) 460.
120
P17
Supported gold catalysts for Preferential oxidation (PROX) of CO in the presence of
excess H2
*
L.F. Liotta , G. Di Carlo, G. Pantaleo and A. M. Venezia
Istituto per lo Studio di Materiali Nanostrutturati, CNR, Via Ugo La Malfa, 90146 Palermo (Italy).
* [email protected]
Objective
Developing efficient catalysts for the selective oxidation of carbon monoxide in the presence of
excess hydrogen is a challenge for the commercial application of low-temperature proton
exchange membrane fuel cells (PEMFCs), where power is generated from the electrochemical
oxidation of hydrogen over an anode electrocatalyst, generally, Pt/C. The production of
hydrogen by steam reforming of methanol or by partial oxidation of liquid hydrocarbons followed
by water gas shift reaction generates gas effluents containing 0.3-1% of CO in an excess of H2
(40-75%) and 20-25% of CO2. Since the CO molecule present in the stream would poison the Pt
anode, it is important to reduce its level below 10 ppm. The preferential oxidation (PROX) of CO
is a possible way to remove such contaminant from the gas stream [1]. Catalysts based on
noble-metals such as Pt, Rh and Ru are generally used for this process, however, quite
recently, gold has received much attention due to its ability to oxidize CO at high rates in the
temperature range of the operating PEMFCs [2]. Several factors such as supported particle
size, gold oxidation state and type of carrier affect the catalytic performance of such catalysts.
In this study the role played by different supports, such as “reducible” (CeO2, TiO2) and “inert”
(γ-Al2O3 and SiO2) oxides was investigated in the CO oxidation in the presence of hydrogen.
With this purpose, catalysts with 1.5 wt% gold loading were prepared by deposition precipitation
method. The morphology, the structure and the electronic properties were determined by X-ray
diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). For the catalytic reaction the
reagent gas mixture consisting of 1% of CO + 0.5% of O2 + 70% of H2 in He was used, with a
-1 -1
weight hourly space velocity (WHSV) of 60 000 mL h g .
Results
Commercial oxides, CeO2, TiO2, γ-Al2O3 and SiO2, with specific surface area ranging between
2
79 and 546 m /g were used as supports. The gold catalysts listed in Table 1, containing 1.5 wt%
gold, were prepared by deposition precipitation method using urea for the silica supported
catalyst and Na2CO3 solution (0.1 M) for the others. The pH of the solution was optimized for
the different supports. The obtained samples were dried overnight at 120°C and tested without
further treatment. The alumina and the silica supported catalysts gave XRD detectable particle
sizes, while highly dispersed gold crystallites (dAu less than 4 nm) were obtained over ceria and
0
titania. According to the XPS binding energies, Au was present on alumina, silica and titania
1+
3+
supported catalysts, Au was found only on the ceria supported one and Au was present in
both, titania and ceria catalysts. The catalytic results in terms of CO conversion and CO
selectivity are reported in Figure 1 for the different catalysts. In accord with our recent results
[3], the gold on ceria showed the highest CO conversion and most important, at variance with
the other supported catalysts, it exhibited a plateau for both, conversion and selectivity, from
90°C up to the highest measured temperatures. Gold on titania was less performing, giving at
50 °C a maximum of CO conversion equal to 40% with a selectivity slightly higher than 40%,
however, both values abruptly decreased by increasing the reaction temperature. The selective
oxidation of CO was further weakened on gold over alumina, showing at 70 °C 30% of CO
conversion and comparable low selectivity. Gold over silica was practically inactive.
121
P17
Table 1. Specific surface area (SBET), average Au particle size (d), XPS Au 4f 7/2 binding energy, XPS
n+
3+
4+
4+
4+
atomic ratio Au/M. (M = Al , Si , Ti , Ce ) and corresponding derived Au loading.
Catalyst
SBET (m2/g)
1.5%Au/γ-Al2O3
1.5%Au/SiO2
1.5%Au/TiO2
155 m /g
2
546 m /g
2
125 m /g
1.5%Au/CeO2
79 m /g
d (nm)
(XRD)
4
6.5
-
2
2
-
n+
Au 4f 7/2 (eV)
Au/M
84.0 (2.1)
84.5 (2.5)
84.3 (1.9) 90%
86.5 (2.3)10%
84.9 (2.4) 83%
87.2 (2.4) 17%
0.003
0.005
0.03
wt% Au
(XPS)
1.1
1.5
7.8
0.03
3.3
Conversion
100
2
- - - Selectivity
6
Au 1.5% Al2O3 (1,2)
Au 1.5% TiO2 (3,4)
80
Au 1.5% CeO2 (5,6)
Au 1.5% SiO2 (7,8)
4
(%)
60
40
3
8
20
5
1
7
0
0
50
100
150
200
250
300
350
400
T (°C)
Figure 1. CO conversion % and CO selectivity % as a function of temperature for the gold supported
catalysts.
Conclusions
Gold on ceria exhibited the best catalytic performance with the highest CO conversion and CO
selectivity which reach a plateau in the range between 90°C and 150°C. Moving to the other
supported catalysts, the CO oxidation in presence of hydrogen increased in the order Au/SiO2<
Au/Al2O3< Au/TiO2. The comparison among the present catalysts highlights the important role in
3+
1+
the CO oxidation played by gold ionic species (Au , Au ) which are better stabilized by cerium
oxide, likely due to a strong metal support interaction. On the other hand, the presence of
metallic gold particles over an “inert” support, like alumina and silica, has proven to give poor
catalytic activity.
Acknowledgements
European Community through (NoE) IDECAT and COST D36 action is acknowledged for
financial support.
References
1. S. H. Lee, J. Han, K. –Y. Lee, J. Power Sources 109 (2002) 394.
2. D. Cameron, R. Holliday, D. Thompson, J. Power Sources 118 (2003) 298.
3. A. M. Venezia, G. Pantaleo, A. Longo, G. Di Carlo, M. P. Casaletto, F. L. Liotta, G. Deganello, J. Phys. Chem. B 109
(2005) 2821.
122
P18
Structure-Reactivity Relationships in ElectronTransfers of Helical Polyaromatic Dications
*ab
a
a
Lubomír Pospíšil , Miroslav Gál , Michal Horáček ,
b
b
b
Filip Teplý , Louis Adriaenssens , Lukáš Severa
a
b
J. Heyrovský Institute of Physical Chemistry of ASCR, v.v.i., Prague, Czech Republic
Institute of Organic Chemistry and Biochemistry of ASCR, v.v.i., Prague, Czech Republic
*
[email protected]
Recent synthesis of various substituted [5]helquats containing five aromatic rings enabled us
the comparison of the electron transfer rates in structures with a different sterical factors. These
compounds are polyaromatics with a helical structure containing two quaternary nitrogens as
heteroatoms. Their structural resemblance to well known diquat inspired us to call them
[1]
helquats. Our previous communication compared the redox properties of helicenes and
[2]
helquats . Compounds with six ([6]helquat) and seven ([7]helquat) aromatic rings were also
prepared.
N
+
+
N
N
+
+
+
N
N
+
N
+
N
N
+
+
N
+
+
N
N
+
N
2+
Helquats (H ) in aprotic solvents are reduced in two subsequent reversible one-electron steps.
The electrochemical impedance spectroscopy was used for determination of very fast
heterogeneous charge transfer rates. The first redox step is slightly slower than the second
electron transfer reaction. This is likely caused by larger inner reorganization energy of the
reduction of the dication to a cation radical, which is much smaller for the second redox step.
Good correlation of reversible potentials and LUMO energy was obtained. Cation radical
●+
generated by the first electron transfer acts as a donor H and forms a charge transfer complex
2+
with the starting oxidized form, the dication, which acts as an acceptor H . The EPR spectra
●+
2+
measured at different concentration ratio of H and H yield the bimolecular electron selfexchange rate. The correlation of the heterogeneous and homogeneous electron transfer rates
in terms of Marcus theory is sought.
Acknowledgement
This research was supported by the Grant Agency of the Czech Rep. (203/09/0705,
203/08/1157 and 203/09/P502) and by the Czech Ministry of Education (COST D36 OC140,
ME09114) and Institute of Organic Chemistry and Biochemistry, ASCR (Z4 055 0506)
References
[1]
[2]
L. Rulíšek, O. Exner, L. Cwiklik, P. Jungwirth, I. iuse, L. Pospíšil, Z. Havlas, J. Phys. Chem. C 2007, 111, 14948.
L. Adriaenssens, L. Severa, T. Šálová, I. Císařová, R. Pohl, D. Šaman, S. V. Rocha, N. S. Finney, L. Pospíšil, P.
Slavíček, F. Teplý, Chemistry Eur. J., 2009, 15, 1072.
123
P18
124
P19
Coke formation during the Methanol-to-Olefin Conversion:
Space- and Time-resolved In-Situ Spectroscopy on H-SAPO-34 and H-ZSM-5
Davide Mores, Eli Stavitski and Bert M. Weckhuysen
*
Inorganic Chemistry and Catalysis Group, Department of Chemistry, Utrecht University, *
*
[email protected]
Introduction and Objective
In-situ spectroscopy is an essential tool for the fundamental understanding of catalytic
reactions. [1-2] However, while most of the applied techniques average the information over the
whole sample, probing a distinct area of a catalyst particle or grain can reveal valuable
information concerning the structure-function relationship during the catalytic action. For this
purpose, micro-spectroscopic methods have been applied.
The selective conversion of methanol into light olefins (MTO) is interesting because it enables
the production of olefins while making use of oil alternative feedstocks. So far, the most
promising catalysts for the MTO reaction are H-SAPO-34 and H-ZSM-5. [3] However, the
reaction suffers from a fast deactivation caused by the formation of carbonaceous deposits.
Here we aim to elucidate the differences in coke formation between large H-SAPO-34 and HZSM-5 individual crystals during the MTO reaction in a space and time resolved manner. This
has been made possible by applying a high-temperature in-situ cell in combination with UV-Vis
and confocal fluorescence micro-spectroscopy techniques. [4]
Figure 3. a) Optical Microphotographs of H-ZSM-5
crystals taken during the MTO reaction at 745K. b)
Corresponding absorption spectra taken from a spot
in the middle of the crystal.
125
P19
Upon exposure of methanol vapour, the
translucent crystals undergo darkening due to
the formation of carbonaceous species. In HZSM-5, coke is initially formed at the triangular
edges, where straight channel openings directly
reach the external crystal surface. During the
reaction, the formation of absorption bands,
assigned to aromatic coke compounds and their
precursors inside the crystal, is observed.
Furthermore, a broad background absorption
that extends over the entire visible region
indicates the formation of graphite coke on the
external surface of the crystal (Figure 1).
Confocal fluorescence microscopy confirms
these observations and shows that fluorescent
carbonaceous species inside the crystal are
initially formed at the near surface area. It is also
observed that while the coke front gradually
diffuses towards the centre of the crystal,
internal intergrowth boundaries hinder the facile
penetration for the more bulky aromatic
Figure 4. fluorescence intensity profiles of H-ZSM-5 compounds (Figure 2).
crystals during the MTO reaction at 660K depicted with
time on stream at laser excitation (a) 488 nm (detection at
510-550 nm) and (b) 561 nm (detection at 565-635 nm).
(c) Schematic representation of the slice where the
confocal fluorescence measurement has been performed.
H-SAPO-34 crystals show two different
temperature regions in which the formation of
different coke species have been observed. In
these crystals, the coke compounds formed
remain mainly at the near surface region of the crystal during the entire course of the reaction.
Here, the formation of polyaromatic coke compounds leads to channel blockage, creating
diffusion limitations for the coke front moving towards the middle of the crystal, thereby making
the internal region of the crystal less accessible to the reactant molecules.
Conclusions
The combination of in-situ UV-Vis and confocal fluorescence micro-spectroscopy is a valuable
tool to probe coke deposits and their precursors during a catalytic reaction. In these molecular
sieves it is shown in a space and time resolved manner that clear differences are observed in
the rate of reaction and the three dimensional distribution of different coke species formed. The
formation of two distinct coke systems i.e. aromatic hydrocarbons in the internal pores and
graphitic coke at the external surface of the crystals is thereby illustrated. The differences in
coke formation are explained in terms of pore architecture and intergrowth structure.
References
[1] J.F. Haw, In-situ spectroscopy in heterogeneous catalysis, Wiley-VCH, Weinheim, 2002
[2] B.M. Weckhuysen, In-situ spectroscopy of catalysis, American Scientific Publishers, Stevenson Ranch, 2004
[3] M. Stöcker, Micropor. Mesopor. Mater. 1999, 29, 3
[4] D. Mores, E. Stavitski, M.H.F. Kox, J. Kornatowski, U. Olsbye, B.M. Weckhuysen,
Chem. Eur. J. 2008, 14, 11320-11327
126
P20
A Neutral State Green Polymeric Electrochromic Based on Acenaphtho[1,2-b]quinoxaline
and EDOT
a*
a
b
Seha Tirkeş , Atilla Cihaner , Melek Pamuk , Fatih Algı
b
a
b
Chemistry Group, Faculty of Engineering, Atılım University, TR-06836 Ankara, Turkey.
Laboratory of Organic Materials, Çanakkale Onsekiz Mart University, TR-17100 Çanakkale,
Turkey.
*
[email protected]
Synthesis and properties of a donor-acceptor type a soluble and stable neutral state green
polymeric electrochromic material was prepared via electrochemical polymerization of a donoracceptor hybrid monomer, namely 8-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-11-(2,3dihydrothieno[3,4-b][1,4]dioxin-7-yl)acenaphtho[1,2-b]quinoxaline (EdAcQ) (Chart 1). The
ambipolar (n- and p-doping processes) properties were attained by incorporation of donoracceptor unit into polymer backbone. As a consequence, a low band gap (1.0 eV) material was
obtained. The corresponding polymer exhibits has a green color in the neutral state and a blue
color when oxidized. In addition, the polymer film dissolved in dichloromethane or acetonitrile
when it is in reduced state.
N
O
N
S
O
S
S
O
O
Chart 1. acenaphtho[1,2-b]quinoxaline based D-A type monomer.
The
voltammogram
of
EdAcQ
in
0.1
M
tetrabutylammonium
hexafluorophosphate
ox
(TBAH)/CH2Cl2 (DCM) solution exhibited an irreversible oxidation peak ( E m , a ) at 0.43 V vs.
Fc/Fc
+
during anodic scan, which was ascribed to the oxidation of external 3,4red
ethylenedioxythiophene (EDOT) units, and a reversible reduction peak ( E m ,1 / 2 ) at -1.49 V
throughout the cathodic scan, which was attributed to the radical anion formation from the
acenaphtho[1,2-b]quinoxaline unit. During repetitive scans a new reversible redox couple with
intensifying current has formed. The observed behaviour indicated the formation of an
electroactive polymer film on the electrode surface.
40.0
30.0
id/mAcm
-2
20.0
10.0
0.0
-10.0
-20.0
-30.0
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
E / V vs. Ag wire
Figure 1. Electropolymerization of 1.0 x 10-3 M EdAcQ in 0.1 M TBAH/DCM at 100mV/s by potential scanning.
127
P20
The PedAcQ in neutral state has three well-defined absorption maxima at 320 nm (3.75 eV),
415 nm (2.89 eV), and 690 nm (1.74 eV) including deep valleys controlling the hue and
1
brightness of the green color . The former two bands (<500 nm) absorb the red color and the
latter band (>700 nm) absorbs blue (Fig. 2).
(b)
+0.85V
+0.80V
+0.75V
+0.70V
+0.65V
+0.60V
+0.55V
+0.50V
+0.45V
+0.40V
+0.35V
+0.30V
+0.25V
+0.20V
+0.15V
+0.10V
+0.05V
0.00V
-0.05V
-0.10V
-0.15V
-0.20V
-0.25V
-0.30V
-0.35V
-0.40V
-0.70V
0.4
0.3
0.2
0.1
400
600
800
1000
0.6
0.5
Absorbance (a.u.)
(a)
0.4
0.3
0.2
0.1
400
1200
600
800
1000
Wavelength / nm
Wavelength / nm
Figure 2. (a) Electronic absorption spectra of the PedAcQ at various applied potentials between -0.7 V and 1.0 V and
(b) the colors of the PedAcQ on ITO at oxidized, neutral, and reduced states in 0.1 M TBAH/DCM.
At low doping levels, the intensities of the three π-π transition bands of PedAcQ decreased
simultaneously and a broad absorption band centered around 810 nm started to intensify due to
the polaron formation. Upon further oxidation, the bipolaron band (at 930 nm) at about 0.50 V
formed, which was also monitored synchronously with cyclic voltammetry, and the polaron band
started to decrease simultaneously. The polymer film caused the color transition from green to
blue during oxidation.
*
The stability of polymer film was studied between neutral and oxidized states by cyclic
voltammetry technique at a scan rate of 200 mV/s. The significant change in redox response of
the polymer was not observed at the end of a thousand cycles. The changes in percentage
transmittance (∆T%) between the neutral (at -0.70 V) and oxidized states (at 1.0 V) were found
as 21.3% for 415nm, 29.0% for 930 nm in the visible region as well as and 33.4% for 1080 nm
in the NIR region. The polymer bearing electrochromic behaviour showed low switching time
and high stability. The researches to obtain neutral state green polymeric electrochromics with
adjusted intrinsic properties are in progress.
References
G. Sonmez, C.K.F. Shen, Y. Rubin, F. Wudl, Angew. Chem. Int. Ed. Engl. 43 (2004) 1498.
128
P21
Molecular structure and reactivity of MoO3/TiO2 catalysts for ethane oxidative
dehydrogenation studied by operando Raman spectroscopy
George Tsilomelekis and Soghomon Boghosian*
Department of Chemical Engineering, University of Patras and
Institute of Chemical Engineering and High Temperature Chemical Processes, Foundation of
Research and Technology-Hellas (FORTH/ICE-HT), Patras, GREECE
Objective
The aim of the present study is to gain insight into the molecular structure of
molybdena/titania(anatase) catalysts and into their catalytic behaviour for the oxidative
o
dehydrogenation (ODH) of ethane at temperatures 420–500 C. Operando Raman
spectroscopy is used for exploring the surface composition of the working catalysts with
simultaneous catalytic measurements. The response of the catalyst constituent MoOx species to
alterations of the catalyst atmosphere is monitored by exploiting the relative Raman band
intensities. The effect of catalyst composition, operating temperature, gas atmosphere, and
reactant residence time on both Raman spectra and catalytic efficiency is studied. Isotopic
18
substitution experiments with O2(g) are used for differentiating between mono-oxo and di-oxo
configurations for the amorphous oxo-molybdenum species.
Results
The properties of the catalysts (synthesized by wet impregnation of anatase with aqueous
solutions (pH = 4–5) using ammonium heptamolybdate as the precursor) are summarized in
Table 1.
Table 1. Catalyst properties
wt% MoO3
3MoTi
3
6MoTi
6
9MoTi
9.1
15MoTi
15
21MoTi
21.1
35MoTi
35
2
TiO2 (calcined) : 97.8m /g
2
Surface Area (m /g)
68.1
80.7
82.5
106.0
107.9
86.3
The in situ Raman spectra obtained for all catalysts
o
under O2 flow at 430 C are shown in Fig. 1. A sharp
-1
band at 992 cm characteristic of Mo=O stretching is
observed, of which the position remains stable with
increasing
loading
and
the
relative
intensity
progressively increases up to the approximate
2
monolayer (15MoTi, 5.9 Mo/nm ). A low presence of
associated species possessing Mo–O–Mo linkages is
evident for the monolayer sample (weak broad band at
-1
~925 cm ). Bulk MoO3 crystals are formed for coverages
exceeding the monolayer (21MoTi, 35MoTi). By
exploiting the Raman band intensities under oxidized
and steady state reaction conditions (for various
residence times) it was found that the reduction of the
Mo=O sites is facilitated with increasing loading.
Mo surface density
2
(Mo/nm )
1.8
3.1
4.6
5.9
8.2
17.0
O2 , 430°C
35%
21%
15%
9%
6%
3%
1200
The combined information of in situ Raman with in situ
FTIR spectra, together with in situ Raman “snap-shots”
(Fig. 2) of catalyst samples subjected to successive
18
reduction/oxidation cycles with H2 and O2 points to a
Crystalline
Phases
TiO2 (Anatase)
TiO2 (Anatase)
TiO2 (Anatase)
TiO2 (Anatase)
TiO2 , MoO3
TiO2 , MoO3
MoO3 / TiO2
Intensity , a.u.
Catalyst
1000
800
600
Raman Shift ,cm
400
200
-1
Figure 1. In situ Raman spectra of
MoO3/TiO2 catalysts at 430oC under flowing
O2(g).
129
P21
mono-oxo molecular configuration, O=Mo(–O–Ti)3 for the dispersed oxo-molybdenum species.
The selective reactivity to ethylene and the ethylene yield are found to increase up to the
monolayer coverage and to moderately decrease at higher loadings. The apparent activity per
Mo atom vs. loading goes over a sharp maximum at the approximate monolayer.
15%MoO3/TiO2
T=450°C
30th
25th
100
21th
3 MoT i
6 MoT i
9 MoT i
1 5MoT i
2 1MoT i
3 5MoT i
90
E th ylene Se lectivity , %
Intensity , a.u.
17th
13th
9th
5th
3rd
1st
80
70
60
50
40
30
20
10
16
O2
0
0
1040 1020 1000 980
960
940
920
900
880
2
4
6
8
10
12
14
16
18
20
22
Conversion , %
-1
Raman Shift , cm
Figure 2. In situ Raman spectra of the
“monolayer” 15MoTi catalyst at 450oC after
successive reduction/oxidation cycles with
H2 and 18O2.
Figure 3. Ethylene selectivity as a function of ethane
conversion for all catalysts at 500oC.
Acknowledgement
Financial support from the Research Committee of the University of Patras (C. Caratheodory
program/C.583) is gratefully acknowledged.
References
[1]. A. Christodoulakis and S. Boghosian S., J. Catal. 260 (2008) 178.
[2]. Tsilomelekis, A. Christodoulakis and S. Boghosian S., Catal. Today 127 (2007) 139.
[3]. A. Christodoulakis, E. Heracleous, A. A. Lemonidou and S. Boghosian, J. Catal. 242 (2006) 16.
130
P22
Nanostructured MoVNbTeO Oxide Catalysts for
Selective Oxidation Reactions
a
b
b,*
a
R. López-Medina , H. Golinska , M. Ziolek , Miguel A. Bañares , M.O. Guerrero-Pérez
c,*
a
Catalytic Spectroscopy Laboratory, Instituto de Catálisis y Petroleoquímica; CSIC; Marie Curie
b
2; E-29049-Madrid (Spain); Adam Mickiewicz University, Faculty of Chemistry, Grunwaldzka 6,
c
60-780 Poznań, Poland; Departamento de Ingeniería Química. Universidad de Málaga; E29071-Málaga (Spain)
Objectives
The reactivity/selectivity properties of the nano catalysts are chemically probed with steadystate catalytic studies of methanol oxidation reactions to determine optimum conditions for
selective oxidation of methanol using MoVNbO and MoVNbTeO supported catalysts on γ-Al2O3
2
containing 4, 8 and 12 atoms (Mo+V+Nb+Te)/nm calcinated in air and inert atmosphere. Also,
the aim of the present work was to study the gas-phase conversion of acetonylacetone in these
catalysts in order to test if acetonylacetone can be used as a sensitive molecule for the
simultaneous characterization of acidic and basic surface properties.
Results
The oxidation of methanol can be used as a probe reaction to characterize the surface acidic
and redox properties of catalysts according to the different products like formaldehyde and
dimethoxymethane, dimethyl ether and carbon oxides indicating the presence of redox, acidic
1,2
and basic sites respectively . Incorporation of Te into MoVNbO improved the activity of
selective oxidation of methanol to formaldehyde on redox sites.
with Te
without Te
with Te
100
90
90
90
80
80
80
70
70
70
60
60
60
50
50
40
40
30
30
20
20
%Selectivity
100
50
40
30
A
B
10
0
10
0
atomic ratio Mo/V/Nb/Te
--
inert
inert
8Mo6V3Nb0.5Te0.5
air
8Mo5V4Nb0.5Te0.5
air
8Mo6V3Nb0.5Te0.5
inert
8Mo5V4Nb0.5Te0.5
inert
8Mo6V3Nb1
air
8Mo5V4Nb1
air
--
inert
inert
4Mo6V3Nb0.5Te0.5
air
4Mo5V4Nb0.5Te0.5
air
4Mo6V3Nb0.5Te0.5
inert
4Mo5V4Nb0.5Te0.5
inert
4Mo6V3Nb1
air
4Mo5V4Nb1
air
4Mo6V3Nb1
4Mo5V4Nb1
0
8Mo6V3Nb1
10
Conversion
Formaldehyde
Dimethyl eter
8Mo5V4Nb1
20
%Conversion
% Conversion/Selectivity
without Te
100
Figure 1. Catalytic activity in MeOH + O2 reaction A) submonolayers coverages catalysts, B) monolayer coverage
catalysts, 0.1 g of catalyst activated in helium flow (40 ml/min) at 400°C for 2 h. Reaction conditio ns: 40 ml/min He/O2/
MeOH (88/8/4 mol%), T = 250°C.
The results of methanol oxidation reaction reveal that there are acid sites on the surface of
2
submonolayer coverages of MoVNb(Te)O catalysts (4 atoms/nm ), at monolayer and monolayer
2
and half coverage (8 and 12 atoms/nm respectively) there are redox sites increased with the
coverage on the surface of the catalysts. The selectivity to redox products is around ~90% and
10 % to acidic products, without the formation of any products originating from surface basic
sites.
The reaction of acetonylacetone, [1,4-diketone (2,5-hexanedione)], is known to undergo both
acid- and base-catalyzed intramolecular cyclizations leading to 2,5-dimethylfuran (DMF) and 31,3,4
methyl-2-cyclopenten-1-one (MCP), respectively . Thus, the incorporation of increasing
amounts of atoms on surface of MoVNb(Te)O oxide causes a continuous decrease in DMF
2
selectivity. Moreover, with the catalysts with 12 atoms/nm , (DMF) was produced at greater
than 60 % selectivity; in contrast with a catalyst even below surface coverage for the supported
2
MoVNb(Te)O (4 atoms/nm ), MCP was obtained with selectivities approaching to 50 % or
better.
131
P22
amount V
3.0
12
amount Mo
at/nm2
A
2.0
at/nm2
1.5
BASIC
8
4
12
4
2,0
at/nm2
1,5
4
8
12
at/nm2
at/nm2
1.0
B
2,5
MCP/DMF
8
2.5
MCP/DMF
amount V
3,0
amount Mo
4
8
acid-base
1,0
ACIDIC
0,5
12
0.5
4
8
at/nm2
8
12
BASIC
acid-base
12
ACIDIC
0,0
0.0
5/4/1
5/4/1
5/4/1
6/3/1
6/3/1
6/3/1
8/1/1
8/1/1
5/4/1
8/1/1
5/4/1
5/4/1
6/3/1
6/3/1
8/1/1
8/1/1
8/1/1
amount V
amount V
3.0
6/3/1
atomic ratio Mo/V/Nb
atomic ratio Mo/V/Nb
3.0
amount Mo
amount Mo
2.5
2.5
4
12
8
MCP/DMF
at/nm2
at/nm2
C
at/nm2
2.0
1.5
12
8
4
at/nm2
1.0
12
8
4
4
acid-base
0.
5
8/
1/
0.
5
BASIC
at/nm2
8
acid-base
12
ACIDIC
5/
4/
0.
5/
0.
5
5/
4/
0.
5/
0.
5
5/
4/
0.
5/
0.
5
6/
3/
0.
5/
0.
5
6/
3/
0.
5/
0.
5
6/
3/
0.
5/
0.
5
8/
1/
0.
5/
0.
5
8/
1/
0.
5/
0.
5
8/
1/
0.
5/
0.
5
5
/0
.
5
5
/0
.
5
/0
.
/0
.
0.
5
0.
5
6/
3/
8/
1/
5
5
/0
.
/0
.
0.
5
0.
5
6/
3/
0.
5
5/
4/
6/
3/
5
5
/0
.
5
/0
.
/0
.
0.
5
12
4
0.0
0.
5
8
1.0
0.0
5/
4/
D
12
BASIC
0.5
5/
4/
8
at/nm2
1.5
0.5
4
2.0
ACIDIC
8/
1/
MCP/DMF
4
Figure 2. Catalytic activity in acetonylacetone cyclisation reaction A) catalysts calcined in air, B) catalysts calcined in
inert, C) catalysts calcined in air with Te and C) catalysts calcined in inert with Te, 0.07 g of catalyst activated in helium
flow (40 ml/min) at 400°C for 2 h. Reaction condit ions: 40 ml/min He, T = 350°C.
Conclusions
The results presented above show that acetonylacetone (2,5-hexanodione) conversion is a
good test reaction to confirm the acid or base surface properties of typical solid acid or base
catalysts. For MoVNb(Te) supported oxide systems, methanol oxidation decreased with
2
increasing surface density MoVNb(Te)O/nm of an oxide supported.
Acknowledgements
The Ministry of Science and Innovation (Spain) funded this study under project CTQ200804261/PPQ. R.L.M. thanks MAEC-AECID (Spain) for his pre-doctoral fellowship. The authors
express their thanks to Olaf Torno (SASOL Germany GmbH) for providing alumina support.
References
[1] I. Sobczak, N. Kieronczyk, M. Trejda, M. Ziolek, Catal. Today 139 (2008) 188
[2] M. Badlani, I.E. Wachs, Catal. Letters 75 3-4 (2001) 137
[3] R.M. Dessau, Zeolites 10 (1990) 205
[4] J.J. Alcaraz, B.J. Arena, R.D. Gillespie, J.S. Holmgren, Catal. Today 43 (1998) 89
.
132
P23
Operando Studies of VPO catalysts in n-butane selective oxidation reaction. Activity,
selectivity and structure transformations.
Ewelina J. Mikolajska, Anna E. Lewandowska, Miguel A. Bañares*
Catalytic Spectroscopy Laboratory, Instituto de Catalisis y Petroleoquimica, CSIC,
E-28049-Madrid, Spain
*
[email protected]
Vanadium phosphates (VPOs) are important catalysts for selective oxidation of alkanes. For
many years they have been the only catalysts in commercial n-butane oxidation to maleic
anhydride, which is a precursor of polyester resins. This selective oxidation reaction follows
Mars and Van Kravelen mechanism, where each metal in different oxidation state plays its own
role in the reaction. According to the mechanism metal cation is reduced by adsorbed organic
molecule and subsequently reoxidized by gas phase oxygen in next step of the reaction.
4+
5+
5+
VPO catalysts contain V as (VO)2P2O7 phase and V as VOPO4 phase. Vanadium (V ) is
probably responsible for formation of maleic anhydride and plays role in a rate determining step
4+
of the selective oxidation reaction of n-butane, while vanadium (V ) is active in formation of byproducts. However, vanadyl phosphate phase is detectable by X-ray photoelectron
spectroscopy in vanadium hydroxide oxide phosphate, a commercial VPO precursor and the
only detectable crystalline phase in commercial catalysts is vanadyl phyrophosphate containing
4+
V cations, that is a major active component of the n-butane oxidation reaction [1,2]. The
5+
presence of VPO4 (V ) phase was also detectable by in situ studies [3].
O1ssatV2p
O1ssat2Vp
VPO calcinated
VPO precursor
5+
V
516,15
523,34
523,90
522,50
512 514 516 518 520 522 524 526 528
counts per second (a.u.)
516,90
4+
V
515,52
counts per second (a.u.)
4+
V
510 512 514 516 518 520 522 524 526 528
BE (eV)
BE (eV)
Figure 1. XPS spectra of VPO precursor (left) and VPO calcinated catalyst (right)
133
P23
929
VPO catalysts may reveal many possible crystalline
phases, like (VO)2P2O7, VOPO4, αI, αII, β, γ, δ, and
metastable ω, and disordered phases [2,4,5]. Their
relative ratio depends on methods of preparation and
catalysts precursor. The ω-VOPO4 phase is stable
only at elevated temperatures and seems to be very
sensitive to reactants and products of butane
oxidation. It transforms rapidly to δ-VOPO4 phase on
butane exposure upon reaction conditions [5].
597
c
2000
1500
794
1032
922
b
392
279
1134
1009
a
270
1184
1088
1016
Besides usually VPO catalysts contain considerable
amount of disordered phases, what makes many
difficulties to understand the nature of VPO catalysts
during catalytic processes and the role of active
sites.
1000
500
-1
Raman Shift, cm
Figure 2. Raman spectra of VPO (a) and used
VPO catalyst, orange molecule (b) and black
molecule (c).
Operando Raman–MS and UV-vis-MS will be used
to observe dynamic changes taking place during
reaction/regeneration cycles. This approach allows
us to study the phase transformations and
characterize changes in activity and selectivity with
variations in composition and structure.
The operando methodology combines in situ
spectroscopy and kinetic measurement in a single
experiment and is thus very convenient for fully
understanding the structure and reactivity of VPO
catalysts during reaction.
References
1. I. E. Wachs, J. of Cat., 170, 55, 1997
2. J. C. Volta et al., J. of Cat., 145, 267, 1994
3. G. W. Coulston et al., Sci. 275, 191, 1997
4. J. C. Volta et al., J. of Cat., 134, 151, 1992
5. G. J. Hutchings et al., Sci. 313, 1270, 2006
134
P24
Theoretical Study of Thiol Self Assembled Monolayer Formation on Au(111) surfaces
Frederik Tielens
a,b*
, Elisabeth Santos
c
a
UPMC Univ Paris 6, UMR 7609, Laboratoire de Réactivité de Surface, 4 Place Jussieu, 75252
Paris Cedex 05, France
b
CNRS, UMR 7609, Laboratoire de Réactivité de Surface, 4 Place Jussieu, 75252 Paris Cedex
05, France
c
Institut für Theoretische Chemie, Universität Ulm, D-89081 Ulm, Germany
π. [email protected]
Introduction
Immersion of a gold surface in thiolate solution leads to a spontaneous adsorption of thiols[1].
These types of layers have attracted much attention because they may constitute ideal
platforms for further binding or reactivity. In the frame of elaborating adjusted surface
functionalities for biocompatibility, biosensor or molecular electronics, special effort was made to
form two-component monolayers, one of the aims being to avoid steric hindrance of functional
tail groups or disorder. Controlling the dispersion of the SAM domains enables to control the
dispersion of e.g. biological systems to be attached on the SAM.
Concerning the initial step in the SAM formation still some questions stay unanswered. After
decades of arguing about the precise site of adsorption of the thiol chains on the gold surface
one start to have a picture on the sorption process. Nevertheless since chemisorption is
generally accepted above physisorption of the thiol molecule, the reaction mechanism is not
known completely. Some theoretical studies have shed some light on the problem. In the
present work the S-H bond breaking mechanism and the formation of the S-Au bond is
investigated using DFT computational techniques. The electronic structure is analyzed and a
possible reaction path is proposed.
The SAMs are modelled using a repeated slab model for Au(111) consisting of five atomic layers
and fixing the two at the bottom to the bulk positions and four thiol chains (See Fig. 1).[2-4] On
the surface HS-C3H7 is adsorbed. The 2√3×2√3R30 unit cell used to build the different mixing
configurations contains four thiol chains. Different configurations were considered after which
the most appropriate are used to model the reaction path for the formation of H2 generated by
the chemisorption process of the thiol to the surface. The transition states between the different
minima on the potential energy surface are calculated using the NEB formalism. A barrier of 1.3
eV is predicted for the H2 formation.
Conclusions
Using first principle computational techniques a new reaction pathway is proposed for the H2
formation as a consequence of thiol chemisorption on Au(111). The thiol adsorption is discussed
in relation with the Au-S bond formation/ S-H bond breaking.
Acknowledgements
The authors thank GENCI project x20090812022 and the CINES, IDRIS and CCRE (Université
Pierre et Marie Curie) for providing the computation facilities. COST D36/0006/06 is
acknowledged for a partial support of this work.
References
1. Poirier, G., Chem. Rev. 97, 1117 (1997)
2. F. Tielens, V. Humblot, Claire-Marie Pradier, M. Calatayud, F. Illas, Submitted to Langmuir
3. F. Tielens, V. Humblot, C.-M. Pradier, Int. J.Quant.Chem, 108, 1792 (2008).
4. F. Tielens, D. Costa, V. Humblot, C.-M. Pradier, J. Phys. Chem. C. 112, 182 (2008).
135
P24
136
P25
Theoretical Investigation of the Ammonia Adsorption Process on (110)-VSbO4 Surface.
a
b
c
Elizabeth Rojas , Mónica Calatayud , M. Olga Guerrero-Pérez , Miguel A. Bañares
a
a
Catalytic Spectroscopy Laboratory, Instituto de Catálisis y Petroleoquímica; CSIC; Marie Curie 2; Eb
29049-Madrid (Spain); Laboratoire de Chimie Theórique, Uni. Paris 06, UMR 7616 CNRS, Paris Fb
75005, France Departamento de Ingeniería Química. Universidad de Málaga; E-29071-Málaga
(Spain):
Introduction
Ammonia is used as reactant in two main classes of reactions of industrial interest: (i) the
ammoxidation of hydrocarbons (alkenes, alkanes, alkylaromatics) to the corresponding organic nitriles
and (ii) the reduction of NO by NH, in the presence of O2. Vanadium based catalysts are efficient for
hydrocarbons (amm)oxidation reactions [1-2]. A very low experimental studies have been made about
the adsorption of NH3 on VsbO4 surface [3]. Even with the large experimental effort applied to the
system, the nature of the NH3-derived adsorbed species has not been definitely determined. Both the
molecular adsorption and dissociative adsorption as NH or NH2 have been proposed. To the best of
our knowledge, no theoretical study of this system has been reported, thus, a theoretical calculation
would be very valuable. In the present work, we will focus on the binding states and adsorption
energies and activation of ammonia on “naked” sites present on the (110)-VSbO4 surface to
understand the role of ammonia in the ammoxidation reaction.
Methodology
Computational Details
The density functional (DFT) calculations were performed by using the Perdew−Wang exchange and
correlation funtionals PW91 functional for the prediction of adsorption energies of ammonia in the
(110)- VsbO4 cluster. Density functional theory using the Perdew−Wang exchange and correlation
functionals PW91 functional can provide useful information about the electronic structure of transition
metal oxides as well as about the interactions between the adsorbed hydrocarbon molecule and the
catalyst surface.
Model
In our theoretical calculation the VSbO4 oxide has been modelled using a trirutile tetragonal super cell
(Fig. 1), which contains the most probably metal-oxygen combinations as reported by Hansen et. Al
[3]. The lattice parameters obtained are: a=b= 4,674 Å and c´= 9,373 Å (c´=3c, c=3,1243 Å). The
plane (110) )- VSsbO4 used in our calculations was chosen because it appears to be one of the most
stable crystal face of oxides of rutile and results from breaking the smallest number of M-O bonds [4] .
A
B
The hypothetical structures, referred as S , S , exhibit two Sb –cations separated by one V cation,
two neighboring V-cations separated by one Sb ion, respectively. Full optimization of all the
constituent atoms of the adsorbate/substrate system was performed. The adsorption energy (Eads) has
been calculated according to the expression:
E ads = E ( adsorbate / substrate ) − E adsorbate + E substrate
Where E(adsorbate/substrate), Eadsorbate, and Esubstrate are the total energies of the adsorbate/substrate
system, isolated adsorbate, and substrate, respectively. A negative Eads value corresponds to a stable
adsorbate/substrate system.
A
Table 1 show parameters of NH3 Adsorption on the “naked” sites of (110)-VSbO4 surface on the S
B
A
B
and S structures. During the NH3 adsorption on the S and S structure, the interaction over a
“naked” surface V atom is energetically most favoured site reached the system a total energy value of
-32.8 kcal/mol (Fig.1).
137
P25
Table.1. Parameters of NH3 Adsorption on the Lewis Acid Sites of (110)- VSbO4 surface.
Structure
S
A
S
B
Adsorption
sites
N-Sb1
N-Sb2
N-V
N-Sb
N-V1
N-V2
Bond
distance
(Ǻ)
2.262
2.832
2.252
2.540
2.227
2.211
Eads
(kcal/mol)
-24.08
-26.20
-32.84
-11.99
-20.53
-21.69
Ammonia adsorption on V(III) site is very exothermic, which is expected considering the
electronically and coordinatively unsaturated V site. There are several possible pathways for
activation of NH3, and the most favourable pathway is one where both hydrogen atoms of NH3
are transferred to the oxygen extra plane that contains the most probable Sb–V combinations
formed OH species. The highest barrier for that process is 28.4 kcal/mol (see Fig. 2). These
results suggest that once the reaction is initiated and V (III) sites start appearing in higher ratios,
ammonia will be activated more rapidly.
+ NH3
O
V
O
O
Sb
O
O
V
O
Sb O
O
V
O
O
V
O
Sb
O
O
V
O
V
O
H
Sb
V
O
V
O
Sb
V
O
H
O
Sb
N
V
O
H
O
Sb O
O
V
O
V
V
O
Sb
V
O
H
0.0
O
V
O
O
Sb
O
O
V
O
Sb O
Sb H
N
V
V
O
O
H
O
V
O
V
-4,4
O
Sb
V
O
- 19.3
O
V
O
Sb
O
O
V
O
Sb O
Sb H
OH
N
V
O
V
O
H
O
V
O
V
O
Sb
V
O
- 32.8
Figure 1. Geometries of ammonia adorptions in the
“naked” surface sites on the (110)-VsbO4 surface. The
values ahown here designate the bond lengths.
Figure 2. Potential energy surface for activation of NH3
on
V
(III)
sites,
∆Eads
(kcal/mol).
Conclusions
The calculated results of ammonia adsorption shows that the “naked” surface V atoms seen to
be more reactive than that of the bulk, suggest that once the reaction is initiated and V (III) sites
start appearing in higher ratios, ammonia will be activated more rapidly.
Acknowledgements
The Ministry of Science and Innovation (Spain) funded this study under project CTQ200804261/PPQ. E. Rojas thanks COST for her STMS program fellowship.
References
[1] Guerrero-Pérez, M.O., and Bañares, M.A., Chem. Matter.,19, 6621 (2007).
[2] Guerrero-Pérez M.O., Bañares M.A., Chem. Commun. 12 , 1292 (2002).
[3] Centi G., Perathoner S., Catal. Rev. Sci. Eng., 40, 175 (1998).
[4] Hansen, S., Stahl, K., Nilsson, R., Andersson, A., J. Solid State Chem. 102, 340 (1993).
[5] Irigoyen B., Juan A., Larrondo S., Amadeo N., Surface Science, 523, 252 (2003).
138
P26
Peculiar response of V2O5-WO3/TiO2 DeNOx catalysts to thermal stress – an
investigation with catalytic and spectroscopic tools
1
2
3
3
Patrick G. W. A. Kompio , Angelika Brückner , Olga Manoylova , Gerhard Mestl , Frank
4
4
1
1
Hipler , Gerhard Auer , Elke Löffler , Wolfgang Grünert
1
Ruhr-Universität Bochum, Lehrstuhl für Technische Chemie, Bochum, Germany
2
Leibniz-Institut für Katalyse e.V., Rostock, Germany
3
4
Süd-Chemie AG, Bruckmühl, Germany. Tronox Pigments GmbH, Krefeld, Germany
Introduction
The selective catalytic reduction (SCR) is a well-established application for the removal of
harmful nitrogen oxides (NOx) from stationary emission sources 1. The reductant ammonia
reduces the NOx selectively to nitrogen (e.g., for NO):
4 NO + 4 NH3 + O2 4 N2 + 6 H2O
The catalyst system typically used contains V2O5 and WO3 supported on TiO2 (anatase) 1. The
vanadium oxide content is often ≤ 1 wt.-% to inhibit the undesired SO2 oxidation 2. WO3
(sometimes MoO3, ≈ 10 wt-%) is a promoter and stabiliser 3. These catalysts, which are
considered technically mature, are very effective, with high NOx conversions and high N2
selectivities between 280°C and 400°C 4. We found, however, that activity resources can be
opened up by optimising the pre-treatment conditions of the catalytic system. Thereby peculiar
and complex responses of the catalytic activity to the thermal stress applied were observed.
Experimental
WO3 and V2O5 were deposited on TiO2 via sequential impregnation of dried titanium oxide
hydrate with ammonium para tungstate and ammonium meta vanadate. The catalytic activity
was investigated in a flow reactor with a feed gas mixture containing 1000 ppm NO, 1000 ppm
-1
NH3, 2 % O2 (balance – helium) at a GHSV of 100,000 h . NO and NH3 were determined via
non-dispersive IR photometry. After appropriate treatments, the catalysts were also studied by
Raman spectroscopy, by EPR and by temperature-programmed reduction (TPR).
Thermal stress applied to the catalysts by a special calcination procedure results in remarkable
changes in the catalytic activity. Up to three activity maxima can be discerned with increasing
pre-treatment severity (see Fig. 1). Depending on the cata-
Figure 1: Change in catalytic activity by increasing pre-treatment duration at 750 °C, a – initial state, calci nation at 350
°C ( □), b – 2nd maximum (), c – minimum (), d – 3rd maximum (), d – final deactivation (). The first maximum is
not resolved at this pre-treatment temperature.
Lyst composition, the peak NO conversions in the activity maxima can be larger (cf. Fig. 1) or
lower than in the initial state. The first or third maxima may escape detection (not resolved at
high, not achieved at low pre-treatment temperature).
Tentative explanations for this complex behaviour will be presented on the basis of characterization results. Raman spectra show the state of the TiO2 in the catalysts to be closer to
139
P26
that of the initial oxide hydrate than to anatase: the anatase finger print is not obtained before
the third activity maximum. The thermal stress results in loss of BET surface area, which
constitutes a declining activity trend onto which the maxima are superimposed. In the initial
state, both EPR and TPR suggest that the surface V oxide species are separated by surface W
oxide species, clustered V surface oxide phases are formed only upon thermal treatment.
Raman and TPR indicate that WOx species segregate upon shrinkage of the support surface
whereas the VOx species appear to remain attached to the support surface. Raman spectra
suggest that the development of the first activity maximum may be related to the formation of a
particular monovanadate surface species. In the EPR spectra, at least two isolated V oxide
species can be differentiated in the initial state and the first maximum. Upon further thermal
stress, a loss of hyperfine structure is accompanied by a growing isotropic signal. The V-O-V
centres indicated by this may be the origin of the second activity maximum (Fig. 1b), whereas
the third maximum (Fig. 1d) is assigned to the formation of the anatase phase. Beyond this
maximum, Raman spectra indicated beginning rutilisation.
References
1.
2.
3.
4.
140
Bosch, H.; Janssen, F.; Catal. Today 1988, 2, 369.
Lietti, L.; Forzatti, P.; Bregani, F.; Ind. Eng. Chem. Res. 1996, 35, 3884.
Cristiani, C.; Bellotto, M.; Forzatti, P.; Bregani, F.; J. Mater. Res. 1993, 8, 2019.
Weisweiler, W.; Chemie Ingenieur Technik 2000, 72, 441.
P27
Synthesis of novel 2:1 permethylated-cyclodextrin-fullerene conjugates
a
a
a
b
c
Zhu Guan , Juan Yang , Yali Wang , Fathi Moussa , Lubomir Pospíšil , Yongmin Zhang
a
a
Université Pierre et Marie Curie-Paris 6, Institut Parisien de Chimie Moléculaire, UMR 7201, 4
place Jussieu, 75005 Paris, France
[email protected]
b
UMR CNRS 8612, Faculté de Pharmacie, Université Paris-Sud 11, 5 rue J.B. Clément, 92296
Châtenay-Malabry, France
c
J. Heyrovský Institute of Physical Chemistry AS CR, v.v.i., Dolejškova 3, 18223 Prague, Czech
Republic
Fullerenes are currently of great interest in many areas of science and technology due to their
unique chemical and physical properties. They appear to be particularly promising in the
biological field, as, for example, functionalised fullerenes can be used as antioxidants and
neuro-protective agents, as well as in photodynamic therapy or for the inhibition of HIV
1
enzymes . The predominant hydrophobic character of the spherical carbon allotrope, however,
hampers solubilization in polar media such as water. Hence, looking for the possibilities to
increase the solubility of fullerenes has become a central topic in synthetic fullerene chemistry.
We prepared recently permethylated cyclodextrin-fullerene conjugates which were highly water2,3
soluble .
However, UV and NMR spectra showed the presence of aggregates and the expected
complexation between permethylated -CD and fullerene was not detected4. In order to
understand the effect of linker length on the complexation between C60 and -CD, two cyclodextrin-fullerene conjugates with shorter linkers were synthesized. The synthetic method
will be presented.
References:
1) S. Bosi, T. D. Ros, G. Spalluto, M. Prato, Eur. J. Med. Chem. 2003, 38, 913-923.
2) J. Yang, Y. Wang, A. Rassat, Y. Zhang, P. Sinaÿ, Tetrahedron 2004, 60, 12163-12168.
3) Y. Chen, Y. Wang, A. Rassat, P. Sinaÿ, Y. Zhao, Y. Zhang, Tetrahedron 2006, 62, 2045-2049.
4) A. Quaranta, Y. Zhang, S. Filippone, J. Yang, P. Sinaÿ, A. Rassat, R. Edge, S. Navaratnam, D. J. McGarvey, E. J.
Land, M. Brettreich, A. Hirsch, R. V. Bensasson, Chem. Phys. 2006, 325, 397-403.
141
P27
142
P28
Electrochemical Functionalization of Glassy Carbon Electrode Surfaces by
Organometallic Moieties
a
b
a
a
a
Giorgio Volpi, Jan Fiedler, Martina Sandroni, Claudio Garino, Roberto Gobetto, Guido
c
a
Viscardi and Carlo Nervi
a
b
Department of Chemistry IFM, via P. Giuria 7, 10125, Turin, Italy. Email: [email protected]
J. Heyrovský Institute of Physical Chemistry of the ASCR, v.v.i., Dolejškova 2155/3, 182 23
Prague 8, Czech Republic.
c
Department of General and Organic Chemistry, via P. Giuria 7, 10125 Turin, Italy.
Objective
NH 2
Transition metal complexes with
interesting photophysical properties
H
NH2
are
currently
under
intense
investigation for their potential
N
O
applications as optically functional
N
materials in a variety of fields such
N
N
as organic light emitting diodes
(OLED),
light-emitting
electrochemical cells (LEC), electrogenerated chemiluminescence, photoinduced hydrogen
production, photoelectrochemical solar cells, and phosphorescent probes/markers for biology.
On the other hand, the functionalization of surfaces is attracting interest because applications
as sensors, molecular electronics, analytical detection, catalysis. The aim of our research during
last years was to investigate the photophysical properties of new Os, Ru, Re and Ir
organometallic complexes [1]. With this knowledge we are now attempting the functionalization
of surfaces by means of organometallic moieties. The goal of the communication is to show our
preliminary results following this pathway.
In the literature there are several examples of molecules covalently bonded on the electrode
surface, but there are very few cases that use organometallic complexes. Carbon is a very
interesting material as nanotubes, fullerene, glassy carbon (GC), pyrolytic graphite, diamond,
etc… Its functionalization by means of strong covalent carbon-carbon bonds found new impetus
only after the work of Savéant et al [2], who used diazonium salts for facile electrochemical C-C
bond formation. Another method is the oxidation of amine [3], which leads to a covalent C-N
bond. Aliphatic amines has been thoroughly employed, but less attention has been paid to the
use of aromatic amines, due to their less (or no) reactivity. One of the aim of this job was to test
the possibility to use ligands containing aromatic amines for organometallic functionalization.
R
Results
N
CO
Six Re(CO)3Cl(pip) [1] and Re(CO)3Cl(dpk) complexes (where
N
pip=1-pyridylimidazo[1,5- ]pyridine and dpk=2-dipyridyl ketone) OC
has been synthesized and fully characterized. The
Re
electrochemical and spectroelectrochemical behaviour of the Re OC
N
derivatives generally show chemically irreversible redox
Cl
processes, but the spectroelectrochemical data suggests a
recombination of the fragment in the OTTLE cell, which leads to a partial reformation of the
starting compounds. The R part (see figure above) can be easily modified in order to include a
suitable functional group (i.e. an aromatic amine) for electrochemical surface reaction. However,
one of our aims was to characterize the modified
+
electrodes by electrochemical methods.
As mentioned, after redox processes these Re
N
N
complexes show weak Re-N bonds. For this reason they
appears to be of limited use because the chemical
Ir
reaction following redox processes might turn them into
N
a weakly surface-bonded derivatives. Therefore, we
switched to Ir and Ru complexes containing aromatic
2
amines and bipyridine-type ligands, known to be more
NH 2 stable and to have a reversible electrochemical
behaviour [1].
143
P28
Commercial (nitroaniline, aminophenanthroline) and synthesized (in figure) aromatic amines
were oxidized at clean GC electrode. Only the latter two apparently undergoes electrode
modification. Hence, their Ru and Ir complexes were synthesized, characterized and electrochemically oxidized on GC. After sonication in pure MeCN, the Cyclic Voltammetries (CV) of the
modified electrodes in MeCN containing only the supporting electrolyte show typical metalcentred redox processes of the corresponding compounds. The surface modification occurs
only for the Ir complex, after the electrochemical oxidation of the amine group. The mechanism
+
takes places via H elimination, and the use of collidine as base facilitates the formation of the
C-N covalent bond. In the presence of collidine also the
2+
Ru complex undergoes the GC modification. The anodic
(Ru) and cathodic (Ir) CV peaks are directly proportional
N
N
to the sweep rate, and integration of the peak areas
Ru
(after background subtraction) allow to evaluate the
–10
N
electrode surface coverage, which are (Ru)=4.6×10
N
–10
2
and
mol/cm . These values are in
(Ir)= 3.5×10
2
agreement with the formation of a monolayer, taking in
account the molecule surface area (evaluated via
NH 2 quantum mechanical calculation).
Conclusions
We electrochemically characterized seven Re derivatives. GC surface modification by means of
aromatic amines has been achieved (also with the help of collidine), and transition metal
complexes having interesting photophysical properties have been covalently attached to the
carbon GC electrode. In a 0.1 M TBAPF6 MeCN solution the modified electrodes show the
same reversible electrochemical behaviour of the free complexes. The properties are retained
even after several redox cycles, outlining the stability of the metal complexes bonded to the GC
surface. Applications can be potentially found in the fields of catalysis, sensors and molecular
electronics.
References
.
[1] G. Volpi, C. Garino, L. Salassa, J. Fiedler, K.I. Hardcastle, R. Gobetto, C. Nervi, Chem.Eur.J., 2009, 15, 6415.
[2] P. Allongue, M. Delamar, B. Desbat, O. Fagebaume, R. Hitmi, J. Pinson, J.-M. Savéant, J.Am.Chem.Soc., 1997,
119, 201.
[3] B. Barbier, J. Pinson, G. Desarmot, M. Sanchez, J.Electrochem.Soc., 1990, 137, 1757.
144
P29
Self–assembled monolayers of atrazine–based thiolates and their interaction with anti–
atrazine antibody.
*,a
*,b
b
Magdaléna Hromadová , Michèle Salmain , Nathalie Fischer-Durand , Viliam
a
a
Kolivoška , Romana Sokolová
a
J. Heyrovský Institute of Physical Chemistry of ASCR, v.v.i., Academy of Sciences of the
Czech Republic, Dolejškova 3, 18223 Prague, Czech Republic
b
Laboratoire de Chimie et Biochimie des Complexes Moléculaires, UMR CNRS 7576, Ecole
Nationale Supérieure de Chimie de Paris, 11 rue Pierre et Marie Curie,
75231 Paris Cedex 05, France
[email protected]
As a part of our objective to build an immunosensor for the detection of pesticide atrazine (ATZ)
in the environmental samples we studied the self-assembly process of atrazine derivative
(ATZSSATZ) on a gold substrate.
Self-assembled
monolayers
of
ATZSSATZ
were
characterized by cyclic voltammetry, ellipsometry, scanning
tunneling microscopy, phase modulated IRRAS, XPS and
N
N
O
(CH2)5
COOEt QCM measurements. Two different time constants for the
N
N
N
NH
adsorption process were observed depending on the
H
H
S
experimental method used. The QCM data reflect the
ATZSSATZ
2 adsorption kinetics of the original disulphide compound,
whereas ellipsometry and ex-situ PM-IRRAS (see Figure 1) refer to the formation of thiolate
monolayers on the gold substrate (ATZS-gold).
Cl
2
addition of anti-ATZ IgG
1.04
0
PM-IRRAS
-2
-1
area ( 3200cm - 2700cm )
6
∆f / Hz
5
4
-1
arbitrary units
1.03
1.02
1.01
3
-4
∆f = -9.6 Hz
-6
2
∆f = +4.8 Hz
-8
1
1.00
-10
0
3000
2000
1500
0
-1
20
40
60
time / min
wavenumber / cm
80
addition of atrazine
100
-12
0
500
5000
5500
6000
time / s
Figure 1
Figure 2
In-situ QCM data (see Figure 2) demonstrate the suitability of such monolayers for the detection
of atrazine in aqueous samples. After the preparation of thiolate monolayers an anti-atrazine
antibody (anti-ATZ IgG) was added, which resulted in full monolayer coverage. Approximately
-5
half of the antibody molecules were displaced from the surface by addition of 10 M atrazine, so
the functional material is suitable for the detection of atrazine in the aqueous samples.
A Grant Agency of the Academy of Sciences of the Czech Republic (IAA400400802), Grant
Agency of the Czech Republic (GACR 203/08/1157 and 203/09/1607) and Ministry of Education
(LC510, COST OC140) are greatly acknowledged for the financial support.
145
P29
146
P30
DNA gel particles from single and double-tail surfactants
1*
1
M. C. Moran , M. G. Miguel , B. Lindman
1
1,2
Chemistry Department, University of Coimbra, 3004-535 Coimbra (Portugal).
2
Physical Chemistry 1, University of Lund, 22100 Lund (Sweden).
*
[email protected]
A general understanding of DNA-oppositely charged agent interactions, and in particular the
phase behaviour, has given us a basis for developing novel DNA-based materials, including
gels, membranes and gel particles[1]. We have recently prepared novel DNA gel particles
based on associative phase separation and interfacial diffusion. By mixing solutions of DNA
(either single- (ssDNA) and double-stranded (dsDNA)) with solutions of different cationic agents,
such as surfactants, proteins and polysacharides, the possibility of formation of DNA gel
particles without adding any kind of cross-linker or organic solvent has been confirmed [2-6].
The adsorption strength, which is tuned by varying the structure of the cationic agent, allows to
control the spatial homogeneity of the gelation process, producing either a homogeneous DNA
matrix or different DNA reservoir devices. They allows for various applications in the controlled
encapsulation and release of ssDNA and dsDNA, with clear differences in the mechanism.
Cationic surfactants have offered a particularly efficient control of properties of DNA-based
particles [2, 6]. This presentation is focused on the formation of DNA gel particles mixing DNA
(either single- (ssDNA) or double-stranded (dsDNA)) with single chain (DTAB) and double chain
(DDAB) surfactants. Results on the encapsulation of DNA and its release are presented, using
the surfactant structure and the DNA conformation as controlling parameters.
References
[1] D. Costa, M. C. Morán, M. G. Miguel, B. Lindman, , Cross-linked DNA Gels and Gels Particles, in R. S. Dias and B.
Lindman (Eds.) DNA Interactions with Polymers and Surfactants,Wiley Interscience, New Jersey, 2008.
[2] M. C. Morán, M. G. Miguel, B. Lindman, Langmuir, 23, 6478 (2007).
[3] M. C. Morán, M. G. Miguel, B. Lindman, Biomacromolecules, 8, 3886 (2007).
[4] M. C. Morán, T. Laranjeira, A. Ribeiro, M. G. Miguel, B. Lindman, to appear in J. Dispersion Sci. Technol., 30 (2009).
[5] M. C. Morán, A. Ramalho, A.A.C.C. Pais, M. G. Miguel, B. Lindman, Mixed protein carriers for modulating DNA
release, Langmuir, accepted (2009).
[6] M. C. Morán, M. R. Infante, M. G. Miguel, B. Lindman, R. Pons, Novel biocompatible DNA gel particles, Soft Matter,
submitted (2009).
147
P30
148
P31
Adsorption of macromolecules to responsive surfaces
1*
2
R.S. Dias, P. Linse, and A. A. C. C. Pai
1
s
1
Department of Chemistry, University of Coimbra, Rua Larga, 3004-535 Coimbra, Portugal
*
[email protected]
2
Physical Chemistry, Centre for Chemistry and Chemical Engineering, Lund University,
S-221 00 Lund, Sweden
Objective
Polymer and protein adsorption onto lipid monolayers and bilayers is of fundamental importance
in biology and pharmacology as well as in a large range of technological processes. However,
membranes are not static, flat and homogeneous objects. The individual lipid molecules in the
membrane undergo rotation, lateral diffusion, and vertical excursions out of the bilayers and into
solution, the so-called protrusions. This will naturally have an impact on the structure of the
membrane itself and on its interaction with biomacromolecules such as DNA and proteins.
The aim of our work is to correlate the adsorption and condensation of a single polyelectrolyte,
a very simplistic model of a DNA molecule, with the properties of a model membrane, namely
the lateral diffusion and protrusion into the solution.
It has been observed previously [1] that the lateral diffusion of the headgroups enhances
significantly the adsorption and condensation of a polyanion. Adsorption appears at net neutral
membranes or at weakly charged membranes, as long as the charges are mobile or frozen in a
random fashion, and it is more pronounced for more flexible PA chains. These results go
beyond the conventional adsorption behavior of a PA at a homogeneously charged surface.
Results
A very simple model was adopted to describe the interaction between a PA and a net neutral
membrane carrying both cations and anions that are able to protrude into solution. The PA is
described as consecutive negatively charged hard spheres connected by harmonic springs,
where its intrinsic stiffness is regulated by an angular potential. More details regarding the PA
model can be found in Ref. [1] and those on the membrane model and simulation details can be
found in Ref. [2].
Figure 1. Left: Number density of the system particles vs.
the z-coordinate. The (semi-flexible) polyelectrolyte beads
correspond to the black line, the distribution of the
membrane particles overlap (blue and green lines) and the
red curves correspond to the polyanions and respective
counterions. The filled curves correspond to the system
with protrusions and the dashed ones to the system without
protrusions. Below is a representative snapshot.
Figure 1 shows the number density of the different particles in the system along the zcoordinate, that is, perpendicular to the membrane, placed at the average position of -148.5 Å.
It can be observed that both the PA beads and the respective counterions can occupy a lower
position in the z-coordinate than those of systems calculated without protrusions (dashed
curves). This indicates that the adsorption of the PA is more favorable in membranes with
protrusions.
149
P31
Table 1 presents some of the properties of the Pas with different flexibilities in the presence of
lipid membranes with and without protrusions. Whereas the presence of protrusions does not
influence substantially the adsorption of the more flexible PA, the adsorption of the semi-flexible
PA is seen to increase. We recall that the more flexible PA showed improved adsorption ability
in the membranes with lipid lateral diffusion due to its ability to concentrate more positive charge
[1]. When lipid protrusions are also present the membrane will presumably be able to adapt to
the stiffer PA, as it has been shown with a spherical macroion [2]. This will enhance the
adsorption of the PA.
Table 1. Average properties of Pas with different flexibilities (flexible, l0 ≈ 7 Å, and semi-flexible, l0 ≈ 22 Å)
prot.
Flexibility
no
no
yes
yes
s-flex
flex
s-flex
flex
27±1
8±1
17±2
4.3±0.3
32±1
36±1
39±1
37±1
23±1
35±1
29±1
36±1
13±3
4±1
7±2
2.4±0.3
in the presence of membranes with and without individual lipid protrusions (prot.).
correspond to the root mean square radius of gyration
onto the membrane normal and based on trains and loop beads
plane, respectively. Nads and Ntails are the number of PA
membrane (i.e. at a distance not larger than 8 Å) and the number
PA’s tails, respectively. Values are given in Å.
and
based on the tails projected
projected on the membrane
segments adsorbed at the
of monomers residing in the
Conclusions
The details of the membrane surface are of great importance for polyion adsorption. Individual
lipid protrusions enhance the adsorption of semi-flexible polyions since the membrane is able to
adapt to the topology of the polyion. In the case of the more flexible PA there is no substantial
improvement in the adsorption ability.
Acknowledgements.
R.S.D. is grateful to Fundação para a Ciência e Tecnologia (Ciência 2007).
References
[1] R.S. Dias, A.A.C.C. Pais, P. Linse, M.G. Miguel and B. Lindman, J. Phys. Chem. B, 109 (2005) 11781.
[2] R.S. Dias and P. Linse, Biophys. J., 94 (2008) 3760.
150
P32
Proton Coupled Oxygen Reduction at Liquid-Liquid Interfaces Catalyzed by Cobalt
Porphine
1,2
1
1
1
3
Imren Hatay, Bin Su, Fei Li, Manuel Alejandro Méndez, Tony Khoury, Claude P.
3
3
2
4
*,1
Gros, Jean-Michel Barbe, Mustafa Ersoz, Zdenek Samec, and Hubert H. Girault
1
Laboratoire d’Electrochimie Physique et Analytique, Ecole Polytechnique Fédérale de
Lausanne, Station 6, CH-1015 Lausanne, Switzerland ; Department of Chemistry.
2
Selcuk University, 42031 Konya, Turkey.
3
Institut de Chimie Moléculaire de l’Université de Bourgogne, ICMUB (UMR 5260), 21078 Dijon
cedex, France.
4
J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic,
Dolejskova 3, 18223 Prague 8, Czech Republic.
Objective
Oxygen reduction catalyzed by porphyrins is of great interest in fields as diverse as biology,
photosynthesis and electrocatalysis[1]. On the other hand, the Interface between Two
Immiscible Electrolyte Solutions (ITIES) provides a physical separation of the reactants and
products, and the polarization of this soft interface also allows an electrochemical control for
different charge transfer reactions[2]. Herein, we show that cobalt porphine (CoP) catalyzes the
reduction of O2 in biphasic systems where the aqueous phase is acidic and where the organic
phase contains electron donors.
Results
Cobalt porphine (CoP) dissolved in the organic phase of a biphasic system is used to catalyze
O2 reduction by an electron donor, ferrocene (Fc). Using voltammetry at the interface between
two immiscible electrolyte solutions (ITIES), it is possible to perform this catalytic reduction at
the interface as a function of the applied potential difference, where aqueous protons and
organic electron donors combine to ultimately reduce O2. Thus, the current signal observed
corresponds to a proton-coupled electron transfer (PCET) reaction, as no current and no
reaction can be observed in the absence of either the aqueous acid, CoP, Fc or O2.
Additionally and given that the oxidation product of ferrocene, namely ferrocenium, does not
cross the interface in the same potential range as that of the PCET reaction and the two
processes can be observed. This is the main difference with voltammetry at solid electrodes
that only records electron transfer steps.
Figure 1. Interfacial PCET mechanism
151
P32
Conclusions
This work shows that voltammetry at soft interfaces is a powerful tool to study proton coupled
electron transfer reactions of biological interest such as the interfacial reduction of oxygen
catalysed by a metalloporphyrin, e.g. Co(II) porphine. As in biosystems, the reactants can be
phase–separated, the protons in the aqueous phase and the electron donors in the organic
phase. In the present, we have reacted an oxygen carrier catalyst, namely cobalt porphine,
aqueous protons and lipophilic electron donors, and shown that voltammetry can be efficiently
used to probe the existence of such an interfacial reaction. This work is to the best of our
knowledge the first voltammetric study of an electrocatalytic reaction at a soft interface, where
the rate of the catalytic reaction is controlled by the interfacial polarization, i.e. by the applied
potential difference. This investigation opens the way to the study of synthetic catalysts able to
carry out the four-electron reduction of oxygen to water.
References
[1]
[2]
152
S. Fukuzumi, S. Mochizuki, T. Tanaka, Inorg. Chem. 28 (1989) 2459-2465.
R. Partovi-Nia, B. Su, F. Li, C. P. Gros, J. M. Barbe, Z. Samec, H. H. Girault, Chem.--Eur. J. 15 (2009) 23352340.
P33
Synthesis of crystalline CeO2 nanoparticles by a novel oil-in-water microemulsion
reaction method and its use as catalyst support
2
3
1
Margarita Sánchez-Domínguez , Gabriella Di Carlo , Magali Boutonnet , and Conxita
2
Solans
1
Kungliga Tekniska Hogskolan (KTH), Department of Chemical Engineering and Technology,
Div. Of Chemical Technology, Teknikringen 42, S-10044 Stockholm, Sweden
e-mail: [email protected],
2
Consejo Superior de Investigaciones Científicas (CSIC, IIQAB)
CIBER en Biotecnología, Biomateriales y Nanomedicina (CIBER BBN)
Jordi Girona 18-26, 08034 Barcelona, Spain.
e-mail: [email protected], [email protected]
3
Institute of Nanostructured Materials,ISMN-CNR,
Via Ugo la Malfa 15390146, Palermo, Italy
e-mail: [email protected]
Introduction
Microemulsions are transparent and thermodynamically stable colloidal dispersions in which two
liquids initially immiscible (typically water and oil) coexist in one phase due to the presence of a
monolayer of surfactant molecules. Depending on the ratio of oil and water and on the
hydrophilic-lipophilic balance (HLB) of the surfactant, microemulsions can exist as oil-swollen
micelles dispersed in water (oil-in-water microemulsions), or water-swollen inverse micelles
dispersed in oil (water-in-oil microemulsions). The characteristic size of microemulsion droplets
is very small (typically below 10 nm).The preparation of nanoparticles using ME systems, due to
its advantage of allowing high control of size, composition and structure of those particles, has
been widely studied, in particular making particles for catalytic, magnetic or ceramic uses and
also in polymer manufacture.The first application of water-in-oil (W/O) microemulsion for the
synthesis of catalytic nanoparticles was introduced in 1982 and concerns nanoparticles of noble
metals. Since this time, this method has found a wide range of applications in the field of
catalysis from room temperature reactions such as iusep isomerisation to high temperature
[1]
reactions such as catalytic combustion of methane .
Recently, we developed a novel and straightforward approach for the synthesis of inorganic
[2, 3]
nanoparticles by using oil-in-water (o/w) microemulsions
, in contrast to the typically used
[4]
water-in-oil microemulsion method . The new strategy implies the use of organometallic
precursors, dissolved in nanometer-scale oil droplets (stabilised by surfactant), and dispersed in
a continuous aqueous phase. In our preliminary work, the o/w microemulsion approach was
explored as proof of concept for the synthesis of metallic and metal oxide nanoparticles. The
studies revealed that metallic nanoparticles (Pt, Pd, Rh) with small diameter (3-6 nm) and
narrow size distribution, as well as nanocrystalline metal oxide (cubic ceria) could be obtained in
mild conditions.
Objective
The aim of this work is to explore the potential of this approach for producing nanocrystalline
[5]
ceria for catalytic purposes
Results
The effect of organometallic precursor on the phase behaviour of several water/nonioic
surfactant/oil systems was first studied in order to identify o/w microemulsion regions. A series
of nano-cerias were synthesized by varying microemulsion composition and reaction conditions.
Characterization studies (Figure 1) demonstrate that nanocrystalline cubic ceria was obtained in
the microemulsion at room temperature (crystallite and nanoparticle size 2-5 nm), with specific
2
surface area (SSA) from 180 up to 250 m /g. The materials were calcined at 400ºC after which
2
high SSA (up to 220 m /g) and small crystallite size (~ 5 nm) were maintained, indicating good
thermal stability. The potential of selected nanocerias as catalyst support was explored in the
CO oxidation reaction. ‘
153
P33
Conclusions
The obtained results demonstrate the feasibility of this approach for the preparation of varied
nanocrystalline cerias with high SSA and small crystallite and nanoparticle size for catalytic
purposes.
after calcination
at 400ºC
after calcination at 400ºC
10 nm
as obtained
(non-calcined)
as obtained (non calcined)
Figure 1. TEM pictures and XRD spectra of ceria nanoparticles synthesized in o/w microemulsions.
References
[1] S.Eriksson ,U. Nylen, S. Rojas, M. Boutonnet. .Preparation of catalysts from microemulsions and their applications in
heterogeneous catalysis Appl Cata-Gen.2004, 265 (2): 207-219.
[2] M.Sánchez-Domínguez; M.Boutonnet, C.Solans, J. Nanoparticle Research 2009, in press, online at Online FirstTM
(DOI 10.1007/s11051-009-9660-8)
[3] C. Solans; M.Sánchez-Domínguez; M.Boutonnet ; Patent Application in the Spanish Patent Office, Application
Number: 200802114(9); Priority Date: 16 July 2008.
[4] M. Boutonnet, S. Lödberg, E. E. Svensson Curr. Opin. Colloid Interface Sci., 2008, 13, 270.
[5] C. Solans; M.Sánchez-Domínguez; M.Boutonnet, PCT Application in the Spanish Patent Office, Application Number
PCT/ES2009/070223; Priority Date: 12 June 2009.
154
P34
The effect of preparation method on the formation of highly active Au-promoter oxide
perimeter in promoted Au/SiO2 catalysts
π.
a*
a
a
b
Beck , A. Horváth , Gy. Stefler , O. Geszti and L. Guczi
a
a
Department of Surface Chemistry and Catalysis, Institutes of Isotopes, HAS, P. O. Box 77,
Budapest, H-1525, Hungary
b
Research Institute for Technical Physics and Materials Science, HAS, P. O. Box, 49, Budapest,
H-1525, Hungary
π. Tel:+36-1-392-2534, Fax:+36-1-392-2703, E-mail: [email protected]
Abstract
Beside the classical deposition-precipitation (DP) method we have applied sol deposition
1,2
technique for preparation of Au/SiO2 that was interfaced with suitable (reducible) oxides only
by decoration. To fabricate a well defined catalyst one of the crucial problems is the active oxide
morphology. We aim at reporting how the structure of a nanocomposite system (uniform
nanosized Au particles with Au/promoter oxide perimeter) benefits the fabrication of a novel
catalyst family.
Gold nanoparticles were fabricated from HauCl4 reduced and stabilized by Na-citrate+tannic
acid or reduced by NaBH4
and stabilised by polyvinylalcohol (PVA) or
poly(diallyldimethylammonium) chloride (PDDA) to produce Au hydrosols of dAu=6-7, 2-3 and 25 nm, respectively. The Au sols were adsorbed on SiO2 support. The Au on SiO2 or SBA-15
3,4
was decorated by 3 different ways. TiO2 promoter was introduced using Ti-isopropoxid or
Ti(IV) bis(ammoniumlactato)dihydroxide (TALH) precursors. CeO2 modified gold samples were
prepared by impregnating Au/SiO2 and Au/SBA-15 by Ce(NO3)2. All samples were calcined to
remove organic residues. The samples were characterized by HRTEM, XPS, XRD and the CO
oxidation was employed as test reaction and the conversion vs. temperature was used to
compare the activity of the various samples.
In comparing the samples prepared in different methods we establish the importance of the
5
amorphous-like TiO2 and CeO2 covering the Au/SiO2 samples . In Fig 1. the HRTEM picture
indeed shows the presence of CeO2 decorating gold particles. It is clearly indicated that the
SiO2 and SBA-15 supported Au catalysts with minute amount of TiO2 or CeO2 improves the
activity as compared with those deposited on pure CeO2 and TiO2 (anatase) as shown in Fig.2.
The activity depends also on the length of the Au-active oxide perimeter, so its controlled
formation has key importance, that is, we also studied how the surface charges and the
electrostatic interactions during the colloidal preparation affect the active interface.
100
90
CO conversion, %
80
70
Au-CeO2/SiO2
Au-CeO2/SBA-15
Au/CeO2
Au-TiO2/SiO2
Au/TiO2
60
50
40
30
20
10
0
0
20
40
60
80
100
120
140
160
180
200
220
o
Temperature, C
Figure 1 HRTEM image of Au-CeO2/SBA-15
Figure 2 CO oxidation conversion curves
155
P34
The active amorphous oxide decoration has an enhanced charge modification and it may
stabilize the small gold particle size. The activity of the Au/MOx perimeter on SiO2 depends not
only on the Au particle size, but the morphology of the oxide component. For highly active
catalysts the controlled formation of the Au/active MOx nanoensembles is desirable. The
formation of this interface can be efficiently favoured by proper selection of the stabilising
agents of the Au colloids, precursor of promoting oxide and the pH in the preparation.
Ackowledgements
The financial support of National Science and Research Fund (OTKA) grants (# T-049564, # F62481, # K-68052) is greatly acknowledged.
References
[1]. A. Horváth, A. Beck, A. Sárkány, Gy. Stefler, Zs. Varga, O. Geszti, L. Tóth and L. Guczi, J. Phys. Chem. B., 110
(2006) 15417
[2]. A. M. Venezia, F. L. Liotta, G. Pantaleo, A. Beck, A. Horváth, O. Geszti, A. Kocsonya and L. Guczi, Appl. Catal. A.,
310 (2006) 114
[3]. L. Guczi, A. Beck, A. Horváth, A. Sárkány, Gy. Stefler, O. Geszti, Studies Surf. Sci. Catal., 172 (2007) 221
[4]. A. Beck, A. Horváth, Gy. Stefler, R. Katona, O. Geszti, Gy. Tolnai, L. Liotta, L. Guczi, Catal. Today, 139 (2008) 180
[5]. L. Guczi, A. Beck, K. Frey, Gold Bulletin, 42 (2009) 5
156
P35
TiO2 and CeO2 promoted Au/SBA-15 in propene total oxidation
a*
b
b
b
a
T. Benkó , A. M. Venezia , L. F. Liotta , G. Pantaleo , A.Beck , L. Guczi
a
a
b
Institute of Isotopes, HAS, P.O. Box 77, H-1525 Budapest, Hungary
Istituto per Lo Studio dei Materiali Nanostrutturati (ISMN)-CNR, Via Ugo La Malfa, 90146
Palermo, Italy
*
[email protected], telephone: +3613922222/3182
Introduction
The development of active catalysts for the total combustion of volatile organic compounds
(VOCs), which are recognised as major contributors to air pollution, is highly desirable from the
viewpoint of environmental protection. In this study the catalytic activity of gold nanoparticles
deposited on the SBA-15 and modified by oxide promoters in propene oxidation was
investigated.
Experimental
Au-MOx (M: Ti, Ce) nanostructures supported by SBA-15 type of support were analysed. SBA15 and alumina-modified SBA-15 as supports was prepared. Gold was deposited on the support
by adsorption of colloidal gold prepared by HauCl4 reduced by NaBH4 and stabilized by PVA or
PDDA. The oxide was introduced via impregnation by Ti(IV) bis(ammoniumlactato)dihydroxide
[1]
(TALH) and Ce(NO3)3 precursors. The oxide is formed during the calcination. The catalytic
activity in propene oxidation is correlated with the composition, structural and CO oxidation
properties of the catalysts. TEM, SAXS, XRD, and BET measurements were performed to
confirm the structure of the catalysts.
The results show the mesoporous structure of both SBA-15 and AlSBA-15 support with high
surface area. The size of the gold particles was investigated by TEM measurements. In the
case of SBA-15 the gold nanoparticles was prevented against strong sintering during the
catalytic test which suggests that the AuNPs are located predominantly inside the pores. The
catalytic activity of the various catalysts was measured in propene oxidation under standard
conditions. The order of the activity: AuSBACe > AuCeO2 > AuAlSBACe > AuAlSBATi >
AuSBA > AuTiSBA > AuAlSBA. The presence of the oxide promoter improves the catalytic
activity.
C3H6 conversion (%) in CO2
100
AuSBACe
AuSBA
AuCeO2
AuTiSBA
AuAlSBATi
AuAlSBA
AuAlSBACe
80
60
40
20
0
50
100 150 200 250 300 350 400 450 500 550 600 650 700 750
T (°C)
Figure 1 Propene oxidation conversion curves [2]
157
P35
Conclusions
Both CeO2 and TiO2 increase the activity of Au/SBA-15 and Au/aluminated SBA-15 in propene
oxidation. CeO2 decoration leads to a higher improvement of the catalytic activity than TiO2
decoration. The promotion effect was higher in cases of AlSBA-15 supported samples. The
activity order in propene oxidation of the samples differs from that obtained in CO oxidation.
The active sites of the two processes should be different.
References
1. A. Beck, A. Horváth, Gy. Stefler, R. Katona, O. Geszti, Gy. Tolnai, L.F. Liotta and L. Guczi, Catal. Today 139 (2008)
180.
2. A. Beck , T. Benkó, A. M. Venezia, L. F. Liotta and G. Pantaleo, L. Guczi, unpublished results, 2008.
158
P36
Selective photo-oxidation of cyclohexane on TiO2: the role of surface characteristics
1
2
2
M. D. Hernández-Alonso , A. R. Almeida , J. A. Moulijn and G. Mul
2
1
2
Environmental Applications of Solar Energy, CIEMAT-PSA, Madrid, Spain
Catalysis Engineering, Delft University of Technology, Delft, The Netherlands
Objective
Cyclohexane is an important commercial product, used to obtain caprolactam for Nylon-6
production, and currently is obtained by liquid phase selective oxidation of cyclohexane at
elevated temperatures and pressures. An alternative to this process is photocatalytic oxidation
of cyclohexane over TiO2 at room conditions. Research has mainly focused on the effect of the
solvent, photon flux, wavelength and particle size on product formation and selectivity. The role
of the catalyst structure on the activity and selectivity to cyclohexanone has also been studied.
On the contrary, catalyst stability has received relatively little attention in the literature. As has
been previously demonstrated, surface carboxylates and carbonates diminish the activity of the
photocatalysts [1,2]. The accumulation of these deactivating species has been proposed to be
the result of consecutive oxidation of a cyclohexyl peroxide intermediate or adsorbed
cyclohexanone. Thus, modification of the TiO2 surface properties could limit the accumulation of
these deactivating compounds by favouring cyclohexanone desorption and/or the conversion of
the cyclohexyl peroxide to the ketone.
The main goal of this study is to evaluate he effect of surface modification on the behaviour of
the photocatalysts in the selective photo-oxidation of cyclohexane. In situ Attenuated Total
Reflectante (ATR)-FTIR spectroscopy was used to follow the reactions [3].
Results
Anatase-structured Ti1-xZrxO2 materials with x = 0.00, 0.01 and 0.06, were prepared by a
reverse microemulsion method, characterized, and tested as catalysts for the selective photooxidation of cyclohexane to cyclohexanone. The surface acidity of the materials was studied by
means of ammonia adsorption microcalorimetry. In situ ATR-FTIR spectroscopy was used to
evaluate the reaction. In Table 1, some physico-chemical characteristics of the samples are
summarized.
As can be observed, Zr incorporation into the anatase lattice enhances the surface acidity of
TiO2 without causing any significant structural or electronic modification. As expected, also the
stability of surface adsorbed water, i. e. the hydrophilicity, was enhanced.
Table 1. Structural and textural properties of the studied materials
Material
TiO2
TZ1
TZ6
*
Formula
SBET
(m2 g-1)
TiO2
Ti0.99Zr0.01O2
Ti0.94Zr0.06O2
52
57
71
Crystal
size
(nm)
12.8
12.6
14.3
Unit cell
volume
(Å3)
135.7
135.9
135.9
n90
(µmol g-1)*
n90/nT
ratio*
34.73
54.64
135.76
0.21
0.36
0.39
n90 = acidity ∆Qads ≥ 90 kJ mol-1; nT = total acidity
159
P36
-2
Cyclohexane Peak area (m )
TiO2
-0,2
TZ1
TZ6
-0,4
-0,6
-0,8
-1,0
-1,2
-1,4
TiO2 Hombikat
0
20
40
60
80
-2
0,0
Cyclohexanone Peak Height (m )
b
a
0,10
Hombikat
TiO2
TZ1
TZ6
0,08
0,06
0,04
0,02
0,00
100
-1
0
20
40
60
80
100
Time (min)
Wavenumber (cm )
Figure 1 Evolution of cyclohexane and cyclohexanone during the photocatalytic oxidation of the alkane, followed by in
situ ATR-FTIR spectroscopy
Figure 1a shows the evolution of cyclohexane during the photo-oxidation reaction on the
different catalysts, while in Figure 1b the total cyclohexanone production as a function of
illumination time is presented. Peak area and peak height values were normalized by
considering the SBET and mass of catalyst employed in the reaction. Commercial TiO2, Hombikat
UV100 was also assayed for comparative reasons.
Conclusions
The increase in the Brønsted acidity, together with the
higher hydrophilicity, proved to be detrimental for
performance (selectivity and stability) in the selective
photo-oxidation of cyclohexane. Apparently, potential
intrinsic catalytic advantages of having higher acidity
are outweighed by the enhanced number of water born
•
OH radicals, inducing non-selective reactions, and
enhanced hydrophilicity leading to slow desorption and
consecutive oxidation of cyclohexanone (Figure 2).
Figure 2 Schematic representation of the qualitative
correlation between surface properties and
photocatalytic performance
References
[1] C. B. Almquist, P. Biswas, Appl. Catal. A : General 214 (2001) 259.
[2] P. Du, J. A. Moulijn, G. Mul, J. Catal. 238 (2006) 342.
[3] M.D. Hernandez-Alonso, A.R. Almeida, J.A. Moulijn, G. Mul, Catal. Today 143 (2009) 326.
160
P37
Porous silicon with gold nanoparticles as laser desorption/ionization mass spectrometry
platform
Sergei Alekseev
a,b*
b
c
d
, Julia Romanenko , Irina Shmygol , Vladimir Lysenko , Vladimir
b
Zaitsev ,
c
a
Valeriy Pokrovsky and Jacques Fraissard .
a
Laboratoire de Physique Quantique, University P. and M. Curie, ESPCI, 10 Rue Vauquelin,
Paris, France
b
Department of Chemistry, National Taras Shevchenko University,64 Vladimirska Str., Kiev,
Ukraine
c
A. A. Chuiko Institute of Surface Chemistry, NAS of Ukraine, 17 General Naumov St., 03164
Kiev, Ukraine
d
Lyon Institute of Nanotechnologies, INL, CNRS UMR-5270, INSA de Lyon, 7 avenue Jean
Capelle, Bat. Blaise Pascal, 69621 Villeurbanne cedex, France
*
[email protected]
Objective
Matrix assisted laser desorption ionization (MALDI) is a soft ionization mass-spectrometry
technique allowing the investigation of large biomolecules [1,2]. However, introduction of the
organic matrix led to the appearance of background ions in the low mass range interfering with
the analysis of small analytes. To tackle this issue surface-assisted laser desorption/ionization
mass-spectrometry (SALDI MS) technique was proposed. It utilizes substrates, which generally
do not signicantly desorb with analytes together, to bring analytes to be desorbed and ionized.
Many effective SALDI-assisted materials were investigated [3]. The porous silicon (PS) is one of
the most popular among them due to its availability and advantageous characteristics (surface
roughness, low thermal and high electrical conductivity, efficient light absorption) [4]. Chemical
functionalization of the PS surface can make the PS surface highly selective for specific analyte
capture and consecutive MS analysis [5]. Another effective SALDI assisted materials for the
analysis of small organic molecules are the nanoparticles of noble metals, such as silver and
gold [6]. In compare with the PS the nanoparticles (NPs) have better stability and may have
enhanced LDI efficiency due to so-called plasmonic effect: the excitation of collective electron
motion under laser irradiation resulting in enhanced photon absorption and huge concentration
of the optical near-field in a small volume. Above mentioned effect resulted in detection of even
single molecule by means of Raman spectroscopy (surface enhanced Raman, SERS).
The deposition of Au NPs on the external surface of the PS should result in the combination of
advantageous characteristics of both substrates, similarly as it was shown previously for the PS
covered with Ag NPs layer [7] and the PS covered by Au layer by means of ion-sputtering [8].
That is why PS-Au NPs composites are promising to be a good candidate substrate for SALDI
platform.
Results
Free layers of meso-porous silicon (approx. 65% vol. porosity, 55 µm thickness and 20 nm
+
mean pore diameter) prepared by anodic etching of p -doped (ρ = 10 m Ω.cm) silicon (100)
wafers as previously described in [¡Error! Marcador no definido.] were used in this study.
Electroless deposition of gold was performed by means of Psi free layers treatment with
ethanolic solutions of HauCl4, the reduction of Au taken place due to interaction with chemically
active surface species of the PS (Scheme 1).
H
Si Si
O
+ Au3+ + 2H2O
Si
OH
Si
+ Au + 3H+
Scheme 1
161
P37
Depending on the reaction conditions (HauCl4 concentration and treatment time) layers of
aggregated Au NPs with 10 – 100 nm mean particle diameter were obtained. The sample of PSAu with approximately 25 nm NPs was used for following LDI MS experiments.
Mass-spectrometric experiment was performed using time-of-flight Autoflex II instrument (Bruker
Daltonics). Peaks of Au clusters were detected in both positive and negative mass spectra of
PS-Au composites (Fig. 1, a-b)
AuAu2-
Au3-
a
Au+
Au4+
Au3+
Au2+
Au5+
b
MB+
284
c
285
MB+
d
200
300
400
500
600
700
800
900
1000 m/z
Figure 1. Negative (a) and positive (b) mass-spectra of PS-Au ionization platform; Spectra of methylene blue from PSAu (c) and from chemically oxidized PS (d).
The intensity of Au cluster peaks drops with increase of Au atoms quantity in the negative
clusters, otherwise the intensities of odd-atom clusters in positive mass-spectrum are
significantly higher, than the intensities of even-atom ones. This regularity probably takes place
+
due to lower stability of cation-radicals (which are even-atom Aun clusters) in compare with the
+
cations without unpaired electrons (which are the odd-atom Aun clusters) in the conditions of
laser desorption experiment.
The cationic dye methylene blue (MB) was studied as a model analyte for PS-Au ionization
o
platform and chemically oxidized (H2O2(35%) : H2SO4, 3:7 vol., 90 C, 15 min) porous silicon
(PS-OX) taken as a reference platform. The mass-spectra of the MB were obtained only in the
positive ions mode for both platforms (Fig. 1, c – d). The intensity distribution of the manifold of
+
peaks in parent ion region (m/z = 284) is not in accordance with the isotope distribution of MB
+
+•
cation (m/z = 284), indicating the reaction of MB reduction/protonation to MBH (m/z = 285).
The intensity of the reduced form peak is much higher for the PS-OX than for PS-Au. Probably,
the desorption/ionization of the MB takes place on the surface of porous silicon for both studied
platforms. In the case of PS-Au platform Au NPs withdraw electrons from silicon resulting in less
efficient reduction of the analyte.
Conclusions
The composites of porous silicon with Au nanoparticles of tunable size were obtained and their
efficiency as SALDI supports was proved. Studies of biologically important small molecules
(antibiotics, metabolites, antioxidant molecules, etc) desorption/ionization is in progress.
References
[1] K. Tanaka, H. ius, Y. Ido, S. Akita, Y. Yoshida, T. Yoshida, iuse iuse. Mass Spectrom. 1988; 2: 151.
[2]. M. Karas, F. Hillenkamp, Analytical Chemistry 1988; 60: 2299.
[3]. D. S. Peterson, Mass Spectrometry Reviews 2007; 26: 19.
[4]. J. Wei, J. M. Buriak, G. Siuzdak, Nature 1999; 399: 243.
[5]. I. V. Shmygol, S. A. Alekseev, O. Yu. Lavrinenko, N. S. Vasilyeva, V. N. Zaitsev, D. Barbier, V. A. Pokrovsky, J.
Mass Spectrom. 2009; 44(8): 1234.
[6]. Y. Chen, G. Luo, J. Diao, O. Chornoguz, M. Reeves, A. Vertes, J. Phys.: Conf. Ser. 2007; 59: 548.
[7]. H. Yan, N. Xu, W. Y. Huang, H. M. Han, S. J. Xiao, Int. J. Mass Spectrom. 2009; 281(1-2): 1.
[8]. L. C. Chen, J. Yonehama, T. Ueda, H. Hori, K. Hiraoka, J. Mass Spectrom. 2007; 42: 346.
162
P38
Matrix synthesis and functionalization of ordered mesoporous carbon by palladium
nanoparticles as potential sorbent for hydrogen storage
a,b
b
b
Vasyl Gerda , Natalia Kobilinskaya , Vladimir Zaitsev , Jacques Fraissard
a
a
Laboratoire de Physique Quantique, University P. and M. Curie, ESPCI, 10 Rue Vauquelin,
Paris, France
b
Department of Chemistry, National Taras Shevchenko University, 64 Vladimirska Str., Kiev,
Ukraine
Ordered mesoporous carbons (OMC) represent a new generation of materials with unique
properties. A number of interesting applications for adsorption, molecular sieving and hydrogen
storage systems can be imagined if carbonaceous materials are constructed with 3-D
interconnected pores. The synthesis of OMC using ordered mesoporous silica MCM-48 as a
matrix has been realised
Here we describe the synthesis principle, structure and physical properties of OMC and the
characterization of these mesoporous carbons by means of XRD, TPDMS, Raman and FTIR
spectroscopies. MCM-48 was prepared by sol-gel synthesis [1] and was used as the matrix for
sucrose carbonization in vacuum at 700, 900 and 1100 °C. The OMC show XRD patterns with
several sharp low-angle reflections corresponding to the cubic phase. The features of step-bystep sucrose carbonization in MCM-48 pores were revealed by FTIR and TPDMS.
2
The OMC exhibit high N2 BET specific surface area (1810 m /g) and a large total pore volume
3
(1.1 cm /g). A typical OMC has uniform mesopores (3 nm) and a certain number of micropores.
The structure and sorption characteristics of the OMC obtained depend markedly on the
conditions of sucrose carbonizsation in the silica matrix.
The OMC obtained were found to have excellent properties for the reversible adsorption of H2.
The introduction of nanodispersed Pd (1 or 5 mass %) into OMC pores increases hydrogen
adsorption by up to 10 %, corresponding only to the absorption by Pd particles.
The resulting high-surface area carbon with uniform pores is a promising advanced material for
several applications, such as adsorption of large molecules, catalyst support, capacitors and
energy storage.
Acknowledgment
o
We
thank
COST
for
financial
support:
agreement N . D36/003/06
“Interfacial functionalization of (bi)-metallic nanoparticles to prepare highly active and
selective catalysts: understanding synergy and/or promotion effect”.
Reference
[1] Q.G. Meng, P. Boutinaud, A.-C. Franville, et al. Microporous and Mesoporous Materials, 2003, 65, pp. 127–136.
163
P38
164
P39
Theoretical studies of hydrogen adsorption mechanism on ZrO2
1,2
1,2
1,2
Olga Syzgantseva , Monica Calatayud , Christian Minot , Mohammad Esmail
3,4
Alikhani
1
UPMC Univ Paris 06, UMR 7616, Laboratoire de Chimie Théorique, F-75005,
Paris, France
2
CNRS, UMR 7616, Laboratoire de Chimie Théorique, F-75005, Paris, France
3
UPMC Univ Paris 06, UMR 7075, Laboratoire de Dynamique, Interactions et Réactivité, F75005, Paris, France
4
CNRS, UMR 7075, Laboratoire de Dynamique, Interactions et Réactivité, F-75005, Paris,
France
Zirconium oxide and its mixed compounds are widely applied in catalysis, fuel cells, ceramic
technologies, gas sensors and photoconductive thin films. Zirconia catalyzes the hydrogenation
reactions of olefins, diens, carbon monoxide, aromatic carboxylic acids, methanol synthesis
from CO/H2 and CO2/H2, as well as dehydrogenation, isomerization, partial oxidation and
dehydration of hydrocarbons, implying C–H bond cleavage. Photolytic decomposition of water
under UV irradiation is known to be promoted by zirconia. Besides, mixed zirconia-containing
oxides exhibit augmented hydrogen storage capacities.
The insight in the interaction mechanism of hydrogen with zirconium oxide, as well as
comprehension of the driving forces of its adsorption constitutes a challenging task.
For this purpose, reaction pathway on hydrogen adsorption on ZrO2 was explored
computationally on Density Functional Theory and Coupled Cluster level applying different
pseudopotentials and basis sets in order to find out its impact on equilibrium geometries and
energy barriers. Intermediate stages of H2 interaction with ZrO2 were revealed. It is shown that
the cleavage of activated H – H bond resulting in the formation of intermediate hydride
structure, which contains Zr – H and O – H groups, is followed by hydroxide Zr(OH)2 formation.
Zirconium hydroxide, in its turn, can undergo water elimination to form ZrO. The rate limiting
step reveals to be the formation of Zr(OH)2. The description of hydrogen adsorption on ZrO2 is
coherent for all the methods, when as the water elimination is not well described by any of
them, requiring the application of multi-reference approaches.
As a conclusion, equilibrium geometries and energy barriers of each consecutive stage are
determined. Computational results are shown to be consistent with experimental ones, available
in literature. The influence of applied methodology on computational results is figured out.
165
P39
166
BOOK OF ABSTRACTS
Section V:
Index of Authors
Abrantes, L.M.
Adriaenssens, L.
Alekseev, S.
Algı, F.
Alikhani, M.E.
Almeida, A.R.
Andreeva, D.
Andreozzi, P.
Arenillas, A.
Arias, M.
Asaro, F.
Auer, G.
Bañares, M.A.
Baranton, S.
Barbe, J.M.
Barrero, A.
Beck, A.
Bedia, J.
Benkó, T.
Blanco-Brieva, G.
Boghosian, S.
Bonincontro, A.
Boutonnet, M.
Brito, R.
Brückner, A.
Bruijninck, P.C.A.
Bulushev, D.A.
Cabrita, J.S.
Calatayud, M.
Campos-Martín, J.M.
Capel-Sánchez, M.C.
Che, M.
Cihaner, A.
Colina, A.
Colomer, A.
Coppola, L.
Cordero, T.
Costa, R.
de Frutos, M.P.
De Persiis, F.
Di Carlo, G.
Dias, R.S
Dragoi, B.
Dzwigaj, S.
Edolfa, K.
Ersoz, M.
Fermín, D.J.
Fernández, A.C.
Fidalgo, B.
Fiedler, J.
Fierro, J.L.G.
Fischer-Durand, N.
Fleisher, M.
Floch, A.
Fraissard, J.
Gaigneaux, E.M.
Gál, M.
Galantini, L.
Gallardo, A.
García, M.T.
69
123
161
63,127
165
159
37, 99, 101
93, 105
49
45
105
139
27,131,133, 137
75
151
109
155, 157
109,111,113
157
87,163
129
105
153
83
139
45
85
69
41,137, 165
35, 87
35
39
63, 127
59
95
105
109,111,113,115
81
87
105
117,121,153
81, 149
55
39, 51
119
151
61
59
49
143
35,67,75,87
145
119
107
25,161,163
107
123
105
113
79, 95
García-García, F.J.
García-Rodríguez, S.
Gargiulo, V.
Garino, C.
Gebbink, R.J.M.K.
Gerda, V.
Geszti, O.
Girault, H.H.
Gobetto, R.
Golinska, H.
Gros, C.P.
Grünert, W.
Guan, Z.
Guczi, L.
Guerrero-Pérez, M.O.
Hansen, S.
Hatay, I.
Hausoul, J.C.
Heras, M.A.
Hernández-Alonso, M.D.
Hipler, F.
Horáček, M.
Horváth, A.
Hromadová, M.
Đçli, M.
Ilieva, L.
Iliopoulou, E.F.
Infante, M.R.
Ivanov, I.
Jagodzinska, K.
Jiménez-López, A.
Kaučič, V.
Khoury, T.
Kobilinskaya, N.
Kolivoška, V.
Kompio, P.G.W.A.
Krtil, P.
La Mesa, C.
La Parola, V.
Lallave, M.
Landa-Cánovas, A.R.
Lappas, A.A.
Lee, I.
Léger, J.M.
Leggio, C.
Leite, L.
Lewandowska, A.E.
Lindman, B.
Linse, P.
Liotta, L.F.
Lisowski, W.
Löffler, E.
López Nieto, J.M.
López-Granados, M.
López-Medina, R.
López-Palacios, J.
Loscertales, I.G.
Lozano, M.
Lozano, N.
Lundberg, D.
Author Index
57
75
91
143
45
163
155
71, 151
143
27, 131
151
139
141
65,155,157
27,131,137
57
151
45
59
159
139
123
155
145
63
37,99,101,119
103
79, 95, 97
37, 99
43
53
21
151
163
145
139
73
93, 105
51
109
57
103
91
23, 75
105
119
133
81, 147
149
117,121,157
99
139
17
47
27, 131
59
109
97
93
81
169
Author Index
Lysenko, V.
Manoylova, O.
Manrisa, A.
Mariscal, R.
Marques, E.F.
Martín-Alonso, D.
Martínez-Huerta, M.V.
Méndez, M.A.
Menéndez, J.A.
Mestl, G.
Méthivier, C.
Miguel, M.G.
Mikolajska, E.J.
Millot, Y.
Minot, C.
Mitjans, M.
Montes de Oca, M.G.
Moran, M.C.
Moran, M.C.
Moreno-Tost, R.
Mores, D.
Moulijn, J.A.
Mourato, A.
Moussa, F.
Mul, G.
Nedyalkova, R.
Nervi, C.
Nicotera, I.
Nogier, J.P.
Ojeda, M.
Oliviero-Rossi, C.
Olsson, U.
Önal, A.M.
Orellana-Rico, M.J.
Pai, A.A.C.C.
Pamuk, M.
Pantaleo, G.
Parvulescu, A.N.
Pászti, Z.
Pavel, N.V.
Peña, M.A.
Pérez, L.
Petrova, P.
Pinazo, A.
Pointner, B.
Pokrovsky, V.
Pons, R.
Pospíšil, L.
Psarras, A.C.
Ranieri, G.A.
Reischl, M.
Ribitsch, V.
Ribosa, I.
Risuleo, G.
Rodríguez-Castellón, E.
Rodríguez-Mirasol, J.
Rojas, E.
Rojas, S.
170
161
139
95
47
83
47
67
151
49
33, 139
39
81, 147
133
39
165
95
61
81,147
79
53
125
159
69
141
159
99
143
105
39
47
105
83
63
53
149
127
37,117,121, 157
45
65
105
67, 75
79,93,95,97
101
79,93,95,97
77
161
79, 93, 97
123, 141
103
105
77
77
95
105
53
109,111,113, 115
27, 137
75
Romanenko, J.
Rosas, J.M.
Ross, J.R.H.
Ruiz, V.
Ruiz-Rosas, R.
Ruppert, A.M.
Sales, J.L.
Salmain, M.
Samec, Z.
Sánchez-Domínguez, M.
Sandroni, M.
Santamaría-González, J.
Santos, E.
Šebera, J.
Severa, L.
Shishido, T.
Shmidlers, A.
Shmygol, I.
Silva, B.
Sobczak, I.
Sobczak, J.W.
Sokolová, R.
Solans, C.
Stana-Kleinschek, K.
Stavitski, E.
Stefler, G.
Stonkus, V.
Su, B.
Sullivan, J.A.
Syzgantseva, O.
Tardan, F.
Teplý, F.
Tielens, F.
Tirkeş, S.
Trejda, M.
Tsilomelekis, G.
Tsiouvaras, N.
Valero, M.J.
Venezia, A.M.
Vera, D.
Vila, F.
Vinardell, M.P.
Viscardi, G.
Volpi, G.
Wang, Y.
Weckhuysen, B.M.
Wojcieszak, R.
Wojtaszek, A.
Yang, J.
Youssry, M.
Zaera, F.
Zaitsev, V.
Záliš S.
Zdenek S.
Zgrablich, G.
Zhang, Y.
Ziolek, M.
161
111,115
85
59
109
41
91
145
73
153
143
47
135
73
123
39
119
161
83
43
99
145
153
77
125
155
119
151
31
165
105
123
51, 135
127
107
129
67
113
37, 55, 117, 121, 157
111
47
79, 95
143
143
141
41,45,125
107
107
141
105
91
161, 163
73
151
91
141
27,43,107,131
COST Chemistry D36 3rd Workshop and 5th Management Committee
BOOK OF ABSTRACTS
Section VI:
Workshop attendees
171
Abrantes, Luisa Maria
Adriana Liberal
Airaksinen, Sanna
Alekseev, Segyi
Almeida, Ana Rita
Andreeva, Donka
Arenillas, Ana
Bañares, Miguel A.
Barbe, Jean Michel
Beck, Andrea
Bedia, Jorge
Benko, Timea
Blanco, Gema
Boghosian, Soghomon
Boutonnet, Magali
Calatayud, Monica
Capel, Maricarmen
Cihaner, Atilla
Colina, Alvaro
Cordero, Tomás
Dzwigaj, Stanislaw
Edolfa, Kristine
Fermin, David J.
Fraissard, Jaques
García, Sergio
Gerda, Vasilyi
Girault, Hubert H.
Golinska, Hanna
Guczi, László
Guerrero-Pérez, M. Olga
Hatay, Imren
Hernandez, Dolores
Horvay, George
Hromadova, Magdalena
Ilieva, Lyuba
Iliopoulou, Eleni F.
Infante, M. Rosa
Ivanov, Ivan
Jaras, Sven
Kallio, Tanja
Kaucic, Venceslav
Kobilinskaya, Natalia
Kompio, Patrick
La Mesa, Camilo
Landa, Angel
Léger, Jean Michel
Lindman, Bjšörn
Liotta, Leonarda
López-Medina, Ricardo
López-Nieto, José Manuel
Mariscal, Rafael
Marqués, Eduardo F.
Martinez de la Cuesta, Pedro
Mendez, Manuel
Menendez, J. Ángel
Mestl, Gerhard
Miguel, Maria
Mikolajska, Ewelina Joanna
Morán, Carmen
Universidade de Lisboa
PID Eng & Tech
Helsinki University of Technology
Kiev Universiy
Utrecht University
Institute of Catalysis (BAS)
Instituto Nacional del Carbón
Instituto de Catálisis y Petroleoquímica (CSIC)
Burgogne University
Chemical Research Center
University of Patras
KTH Chemical Science and Engineering
Université Pierre et Marie Curie
Atilim University
Universidad de Burgos
Kristine Latvian Institute of Organic Synthesis
University of Bristol
Laboratoire de Physique Quantique –
ESPCI
Kiev Universiy
Ecole Polytechnique Federale de Lausanne
Adam Mickiewicz University
Selcuk University
CIEMAT-PSA
Budapest University of Technology and Economics
Portugal
Spain
Finland
Ucrania
Netherlands
Bulgaria
Spain
Spain
France
Hungary
Spain
Hungary
Spain
Greece
Sweden
France
Spain
Turkey
Spain
Spain
France
Latvia
United Kingdom
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France
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Spain
Ucrania
Switzerland
Poland
Hungary
Spain
Turkey
Spain
Hungary
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J. Heyrovský Institute of Physical Chemistry of ASCR
Czech Republic
CPERI/CERTH
Bulgary
Greece
Spain
Bulgary
Sweden
Finland
Slovenia
Ucrania
Germany
Italy
Spain
France
Sweden
Italy
Spain
Spain
Spain
Portugal
Spain
Switzerland
Spain
Germany
Portugal
Spain
Portugal
Instituto de Química avanzada de Cataluña (CSIC)
Chemical Technology, KTH
National Institute of Chemistry
Kiev University
Ruhr Universitaet Bochum
Sapienza University
Instituto de Ciencia de Materiales de Madrid
Université de Poitiers
University of Lund
ISMN-CNR
Instituto de Tecnología Química (CSIC)
University of Porto
Ecole Polytechnique Federale de Lausanne
Instituto Nacional del Carbón
SÜD-CHEMIE AG
Coimbra University
Coimbra University
Workshop attendants
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173
Workshop attendants
Mores, Davide
Mul, Guido
Murtomäki, Lasse
Nervi, Carlo
Pantaleo, Giuseppe
Parvulescu, Andrei
Parvulescu, Vasile
Parvulescu, Viorica
Pinazo, Aurora
Pons, Ramon
Pospisil, Lubomir
Prieto Barranco, José
Ranieri, Pino
Ribitsch, Volker
RodriguezCastellón, Enrique
Rodríguez-Mirasol, José
Rojas, Elizabeth
Rosas, Juana M.
Ross, Julian
Ruiz-Rosas, Ramiro
Rus Martínez, Eloisa
Samec, Zdenek
Schoonheydt, Robert
Sobczak, Izabela
Sousa Dias, Rita
Sullivan, James
Syzgantseva, Olga
Tielens, Frederik
Tirkes, Seha
Trejda, Maciej
Tsiouvaras, Nikos
Valero-Pedraza, M. José
Valero-Romero, M. José
Venezia, Anna M.
Wojtaszek, Anna
Wolfgang, Grünert
Zalis, Stanislas
Zgrablich, Jorge
Zhang, Yongmin
Ziolek, Maria
174
Utrecht University
Delft University of Technology
Dipartimento di Chimica IFM
ISMN-CNR
Utrecht University
University of Bucharest
Institute of Physical Chemistry I.G. Murgulescue
J. Heyrovsky Institute of Physical Chemistry
PID Eng & Tech
Sapienza University
Universitat Graz
University of Limmerick
Heyrovski Institute Prague
Catholic University of Leuven
University of Coimbra
University College Dublin
Atilim University
ISMN CNR
Ruhr-Universität Bochum
Heyrovski Institute Prague
Instituto de Física Aplicada (INFAP)
Netherlands
Netherlands
Finland
Italy
Italy
Netherlands
Romania
Romania
Spain
Spain
Czech Republic
Spain
Italy
Austria
Spain
Spain
Spain
Spain
Ireland
Spain
Spain
Czech Republic
Belgium
Poland
Portugal
Ireland
France
France
Turkey
Poland
Spain
Spain
Spain
Italy
Poland
Germany
Czech Republic
Argentina
France
Poland
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here the book of abstracts

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