Microkinetics assisted design and optimization of catalytic reactions

Transcription

Microkinetics assisted design and
optimization of catalytic reactions
and reactors
Joris W. Thybaut
Laboratory for Chemical Technology, Ghent University
http://www.lct.UGent.be
6th IDECAT/ERIC-JCAT Conference on Catalysis (IEJCat-6), 3rd-6th March 2013, Brixen (Italy)
1
microkinetic modelling
multi-scale modelling
• detailed
• global
• synergy between various scales
2
industrial scale transformation of chemicals
3
Single-Event MicroKinetics (SEMK)
complex mixtures
• reaction families
entropy
energy - enthalpy
– reaction types
• alkyl shift, protonated
cyclopropane branching,
β-scission,…
• H-addition/elimination,…
– intermediate stability
• carbon atom type
• next nearest neighbour
effects
σreactant
 S0,#
kb T
global
k #
exp 
σ global h
 R

 H0,# 
 exp  

 RT 

J.W. Thybaut and G.B. Marin, J. Catal. 50th anniversary, submitted
4
rational catalyst design
performance testing
2
catalyst library
activity library
modelling
synthesis
3
1
industrial
application
new
concept
optimized
descriptors
kinetic and catalyst
descriptors
H
3
H
H
6
H
k(1,2)
H
k(2,2)
1
k(0,2)
H
2
k(2,2)
k(2,2)
k(1,2)
H
4
H
k(0,2)
7
k(1,2)
*
*
design
H
*
k(1,2)
H
H
k(1,2)
k(2,2)
4
9
H
*
H
*
H
H
k(2,2)
*
12
*
H
k(0,2)
H
k(1,2)
H
H
10
k(1,2)
H
k(2,2)
*
H
H
H
13
H
k(0,2)
H
H
H
H
H
H
k(0,2)
H
k(1,2)
H
*
H
H
k(0,2)
H
8
5
11
*
H
*
*
H
*
H
H
J.W. Thybaut et al. Topics Catal. 52 (2009) 1251-1260
5
outline
• introduction
• methanol-to-olefins conversion
– reaction network
– kinetic and catalyst descriptors
– reaction pathway analysis
– assessment of zeolite framework effects
• alternative cases
• conclusions
6
methanol to olefins
MTO process provides an alternative route to produce olefins/gasoline.
Coal
Synthesis Gas
Production
Methanol/
Oxygenates
synthesis
Natural gas
MTO/MTH
and
higher
olefins
Biomass
7
OCMOL project
CO, H2
Oxygenate
synthesis
Oxygenate
to liquids
Liquid
fuels
RM reactor
Step 3
Autothermal
coupling
CH4
OCM reactor
Separation
O2
C2H4
Step 1
Step 2
Ethylene
oligomerization
reactor
Liquid
fuels
Step 4
OCM (Oxidative Coupling of Methane) and RM (Reforming of Methane)
• alternative production route for liquid
hydrocarbons and fuels
• exploitation of small gas reservoirs
– stranded natural gas
– biogas
– landfill gas
http://www.ocmol.eu
8
methanol to olefins catalysts
CHA structure
SAPO-34
C2H4
MFI topology
ZSM-5
C3H6
MTT topology
ZSM-23
C3H6
C3H6
C2H4
C2H4
Aromatics
Aromatics
Aromatics
Teketel et al. ACS Catalysis 2 (2012) 26-37
9
global MTO reaction scheme
DME
Formation
Higher Olefins
Formation
Primary Hydrocarbons
Formation
CH3OH2 +
CH4 + HCHO + H+
DMO+
H+ + DME
C3=
(*) formation of hydrocarbon pool species is not considered.
C5 Olefins
isomerization
C6 Olefins
isomerization
β-scission
CH3OH
HYDROCARBON
POOL*
Methylation & Alkylation
CH3+
C4 Olefins
isomerization
C2=
C7 Olefins
isomerization
10
challenges addressed
• identification of reaction
mechanism in
elementary steps for
– DME
– light olefin
– higher olefins
Trimethyl
benzene
Aromatic
hydrocarbon
pool
Toluene
MeOH/DME
Cyclization and
hydride transfers
Ethene/Propene
and aromatics
Alkanes
Higher
• quantification of reaction
alkenes
Ethene and
Alkene
pathways on ZSM-5 and
higher alkenes
homologation
cycle
ZSM-23
Ethene
• simulation of industrial
reactor behaviour
Bjorgen et al., J. Catal. 249 (2007) 195-207
11
aromatic hydrocarbon pool (exocyclic methylation route)
Z-CH3
+ Z-H
+
+
+
Z-
+ Z-
+
+
Z-
Z-CH3
+
+ Z-H
+ Z-
ZCH3
+ Z-H
Aromatic hydrocarbon pool acts as active center for light olefins and get regenerated.
T. Mole et al. J. Catal. 82 (1983) 261 and J.F. Haw et al. Acc. Chem. Res. 36 (2003) 31712
alkene homologation cycle
ZSM-5
ZSM-23
Methylation
Alkylation
/β-scission
Protonation
/Deprotonation
Hydride shift
Two additional pathways
related to secondary to
primary and tertiary to
primary cracking
Methyl shift
PCP branching
13
reaction network on H-ZSM-5 catalyst
Reaction network in terms of elementary steps for ZSM-5 catalyst:
Number of Species
(Cyclic) Olefins/DME/H2O
Carbenium ions
Aromatics
Total
Number of elementary steps
Protonation
Deprotonation
Hydride shift
Methyl shift
PCP branching
Methylation
Demethylation
Alkylation
Dealkylation
β-scission
hydration
dehydration
Total
DME
formation
3
3
Higher olefins
formation
50
41
6
Primary olefins
formation
4
5
1
10
3
3
3
3
71
71
40
15
54
22
3
3
2
2
91
15
6
1
1
8
16
294
Surface methoxy and DME formation:
2 quasi-equilibrium reactions
(protonation of MeOH and DME)
2 reversible reactions
6 adjustable parameters
Methane formation:
Irreversible reaction
Primary olefins formation:
8 reversible reactions
1 total concentration of hydrocarbon pool
Higher olefins formation:
1 Irreversible reaction (methylation)
1 reversible reaction (alkylation)
- 6 activation energies based on stability
of carbenium ions
-6 olefin protonation enthalpies depending on
number of carbon atoms from O2 to O7
14
activation energies and protonation enthalpies on ZSM5
(T = 360 - 480 0C, Pt = 1.04 bar and W/FMeOH = 0.5 - 6.5 kgcat.s mol-1)
Activation energy
Forward
Reverse
(kinetic descriptors)
(kJ/mol)
(kJ/mol)
Protonation
enthalpy
(kJ/mol)
(catalyst descriptors)
Surface methoxy, and DME formation
Dehydration
222.7 ± 8.1
170.4 ± 15.6 Methanol
-61.8 ± 3.8
Protonation with MeOH
138.6 ± 7.5
163.7 ± 14.8 DME
-42.8 ± 8.1
Methane formation
Methane formation
121.1 ± 18.4
Hydrocarbon pool species formation
Methylation of p-xylene
101.5 ± 1.1
123.2 ± 17.1
Deprotonation of TMeB+ and DMeEtB+
156.7 ± 9.6
123.1 ± 16.8
Methylation of DMeMCHDE and DMeEtCHDE
75.5 ± 16.9 151.8 ± 17.4
Dealkylation of DMeEtB+ and PDMeB+
84.2 ± 8.2
Deprotonation of PX+
143.4 ± 20.8 123.9 ± 16.8
14.1 ± 2.4
P. Kumar et al. Ind. Eng. Chem. Res. 52 (2013) 1491-1507
15
model parameters
Activation energy
(kJ/mol)
(kinetic descriptors)
Protonation enthalpy/ CHP (kJ/mol)/(mol/ kgcat)
Methylation (p-p)
131.9 ± 28.2
(catalyst descriptors)
Ethene
Methylation (p-s)
92.8 ± 10.9
Propene
-42.5 ± 7.6
Methylation (p-t)
54.9 ± 9.2
Butene
-53.9 ± 9.0
Alkylation (s-s)
138.0 ± 9.4
Pentene
-61.6 ± 15.1
Alkylation (s-t)
119.7 ± 17.6
Hexene
-67.7 ± 2.1
Alkylation (t-s)
167.6 ± 28.6
Heptene
-70.3 ± 12.4
CHP
3.47 × 10-2
-11.1 ± 0.16
• activation energies in line with reactant and product stability
• stable intermediates have more negative protonation enthalpies
P. Kumar et al. Ind. Eng. Chem. Res. 52 (2013) 1491-1507
16
simulation results
Parity diagram of experimental vs calculated outlet MTO products flow rates at T =
360 - 480 0C, Pt = 1.04 bar and W/FMeOH = 0.5 - 6.5 kgcat.s mol-1. line: experimental;
: obtained from model regression
17
performance curves
Experimental and model calculated yield of MTO
products at T = 400 0C and Pt = 1.04 bar. Symbols:
experimentally observed values, ethene (), propene
(▲), butene (■); lines: calculated
Experimental and model calculated yield of MTO
products at T = 400 0C and Pt = 1.04 bar.
Symbols: experimentally observed values,
pentene (), hexene (▲), heptene (■), methane
(); lines: calculated
Experimental and model calculated yield of primary
olefins at methanol conversion = ~65% and Pt = 1.04
bar. Symbols: experimentally observed values, ethene
(), propene (▲); lines: calculated
Experimental and model calculated yield of olefinic
products at T=360 0C, Pt = 1.04 bar and W/FMeOH =
4.28 kgcat.s mol-1.
18
contribution analysis
Contribution analysis for MTH on H-ZSM-5 catalyst
at space time of 2.21 kgcat.s/mol and at 400 0C, conversion=66.9%
19
contribution analysis: temperature effect
at space time of 2.21 kgcat.s/mol and at 400 0C,
conversion=66.9%
Contribution analysis MTH on H-ZSM-5 catalyst
at space time of 1.40 kgcat.s/mol and at 480
conversion=73.6%
0C,
20
activation energies, protonation enthalpies on ZSM-23
(T=400 0C, Pt= 1.04 bar, Weff/FMeOH =15.1-50.9 kgcat.smol-1)
(kJ.mol-1)/
Protonation
(mol.kgcat -1)
enthalpy/ CHP
Activation
(kJ.mol-1)
energy
Ethenea
-11.1±0.16
-10.3 ± 1.2
Methylation(p-p)
131.9
Propeneb
-42.5±7.6
-49.9 ± 5.4
Methylation(p-s)
92.8
Buteneb
-53.9±9.0
-55.9 ± 12.6
Methylation(p-t)
54.9
Penteneb
-61.6±15.1
-60.3 ± 8.2
Alkylation(s-s)
138.0
Hexeneb
-67.7±2.1
-64.1 ± 9.4
Alkylation(s-t)
119.7
Alkylation(t-s)
167.6
Alkylation (s-p)
174.5 ± 41.2
Alkylation (t-p)
197.7 ± 46.5
ΔH(s-p)
a
b
to primary carbenium ion,
to secondary carbenium ion
-31.2 ± 6.4
21
performance curves
30
100
25
20
% yield
60
15
10
5
propene
40
ethene
20
0
% conversion
80
oxygenates
Symbols: experimentally
observed values
lines: calculated
0
20
26
32
38
44
effective space time (kgcat.s/mol)
50
35
pentene
30
25
C6+
% yield
14
20
butene
15
10
5
methane
0
14
20
26
32
38
44
effective space time (kgcat.s/mol)
50
22
contribution analysis: framework effect
at space time of 2.21 kgcat.s/mol and at 400 0C,
conversion=66.9%
Contribution analysis for MTO on ZSM-23 catalyst at
T= 400 0C and Weff/FMeOH = 24.8 kgcat.smol-1
conversion=50.2%
23
MTO industrial reactor simulation
ZSM-5 @ 450°C
ZSM-23 @ 400°C:
potential benefits of co-feeding
24
outline
• introduction
• methanol-to-olefins conversion
• alternative cases
– methane aromatization
– xylene isomerization/ethylbenzene
dealkylation
– long alkane hydrocracking
• conclusions
25
methane aromatization
973K, Mo/HZSM-5
K. Wong et al. Micro. Meso. Mater 164 (2012) 302-31226
from steady state to dynamic simulations
0.10
Stage 2: optimal
methane aromatisation
-1
Flow rate (mol s )
0.08
Stage 1: development
of active catalyst form
0.06
0.04
Stage 3: catalyst
deactivation
CO
CO2
-1
0.6
C2H4
0.4
-2
deactivation
CH4 + MoC → H2 + ‘coked’ MoC
C6H6 + H+ → H2 + coked H+
Flow rate 10 (mol s )
0.02
activation
CH4 + 2MoO3 → CO2 + 2H2 + 2MoO2
3CH4 + MoO2 → 2CO + 6H2 + MoC 0.00
0.2
C2H6
0.0
0
5000
10000
Time on stream (s)
15000
27
zeolite framework effects
Catalyst
Max.
sphere
diameter
(Å)
Vmicro
(cm3/g)
Brønsted
acidity
XCH4 (%)
Benzene
Yield (%)
ΔH Phys
C6
kdeact acid
sites
Mo/IM-5
7.34
0.125
188
6.2
3.7
-95
2.17E-05
Mo/ZSM-5
6.36
0.120
143
9.0
5.5
-91
7.62E-06
Mo/TNU-9
8.46
0.132
83
8.0
5.6
-80
6.73E-06
Mo/MCM-22
9.69
0.156
137
9.2
7.2
-63
2.75E-06
physical adsorption and related deactivation effects
28
xylene isomerization: SEMK model
Xylene isomerization on a bifunctional Pt/H-ZSM-5 catalyst
Reaction network consists out of:
• acid catalyzed reactions:
(de-)protonation,
alkyl shift (MS),
dealkylation, (DA)
transalkylation (TA)
• metal catalyzed reactions:
Hydrogenation (HYD)
• physisorption
K. Toch et al. Appl. Catal. A-Gen 425 (2012) 130-144
29
xylene isomerization: results
Successful estimation of the kinetic parameters
• small confidence interval
• physically meaningful
importance of the reactions
HYD << TA << DA ~ MS
order of activation energies:
ΔS
A
DA
>0
105 Aref
Monomolecular
MS
0
Aref
Monomolecular
TA
<0
10-3 Aref
Bimolecular
HYD
-
102 Aref
Bimolecular, number
of active sites
Ea,DA >> Ea,MS ~ Ea,TA >> Ea,HYD
Successful description of the responses
30
xylene isomerization: catalyst optimization
acid strength modifications: ΔHpr is varied from -60 … -110 kJ mol-1
What is of industrial relevance?
maximization of PX content
minimization of xylene losses
120
100
maximization of benzene yield
16
100
14
90
80
12
60
653K, 1MPa
8
673K, 1MPa
673K, 1MPa
-70
-80
-90
ΔHpr (kJ mol-1 )
-100
-110
633K, 1MPa
653K, 1MPa
20
673K, 1MPa
10
0
-60
50
30
2
0
60
40
4
653K, 1MPa
20
633K, 1MPa
6
633K, 1MPa
40
70
10
YB (%)
XXYL (%)
ATEPX (%)
80
0
-60
→ definition of profit function Ψ:
-70
-80
-90
ΔHpr (kJ mol-1 )
-100
-110
-60
-80
-90
ΔHpr (kJ mol-1 )
-100
-110
7000
6000
633K, 1 MPa
653K, 1 MPa
5000
673K, 1 MPa
Ψ
ATEPX S B H pr


 max
X XYL
-70
4000
3000
→ ΔHpr(opt) ≈ ΔHpr(est)
(catalyst used = industrial catalyst)
2000
1000
0
-60
-70
-80
-90
ΔHpr (kJ mol-1 )
-100
-110
31
long alkane hydrocracking over BETA
USY
n-octane
BETA
n-hexadecane
B. Vandegehuchte et al. Appl. Catal. A-Gen 441 (2012) 10-20
32
shape selectivity
Transition state shape selectivity during
Ethyl branch formation
+
rAS = kAS CR+
1,2 alkyl shift
0 exp
kAS = kAS
-(Ea;AS + ∆Ea)
RT
+
2.5E-07
21.9 (± 1.0) kJ
Ea;AS
Fmod (mol s-1)
Energy
∆Ea
mol-1
79.8 kJ mol-1
b
2.0E-07
1.5E-07
1.0E-07
5.0E-08
0.0E+00
0.0E+00
+
5.0E-08
1.0E-07
1.5E-07
2.0E-07
2.5E-07
+
Fexp (mol s-1)
Reaction coordinate
33
adsorption saturation: size entropy
Entropic effects favor the component with the lowest carbon number at
saturation loadings as smaller molecules fit more easily in the gaps
within the zeolite matrix.
Krishna et al. Chem. Eng. J., 2002
0
Linear approximation of -∆Ssiz
80
↗
70
60
50
=0
↗
40
30
↘
20
10
0
4
6
8
10
12
14
CN ↗
34
outline
•
•
•
•
introduction
methanol-to-olefins
alternative cases
conclusions
35
conclusions
• versatility of the SEMK methodology has
been demonstrated (MTO, aromatization,
isomerisation and cracking)
• contribution analyses provide
unprecedented insight in reactant and
product ‘flows’
– reaction path analysis
– reaction mechanism elucidation
– formulation of guidelines for reactor operation
36
conclusions
• zeolite framework and acid strength
effects have been quantitatively assessed
– physical adsorption
– protonation
– deactivation
37
perspectives
• ‘Pleiade’ of future applications
– hydrocarbon chemistry
• hydroisomerisation including diffusion
• ethylene oligomerization
– ‘renewables’ chemistry
•
•
•
•
•
ethanol to hydrocarbons
aldol condensations
glycerol hydrogenolysis
stabilization/hydrodeoxygenation
…
• accounting for O as hetero-atom
• potential stereochemistry effects
• reaction families to be revisited
38
acknowledgements
• Methusalem program/Special Research
Fund (Flemish Government/Ghent
University)
• EC FP7 (OCMOL, NEXT-GTL)
• FWO (NSF)
• IAP (Belgian Science Policy)
• Shell
• …
39
acknowledgements
•
•
•
•
•
Prof. Guy B. Marin (director LCT)
Pravesh Kumar (MTO)
Kae Shin Wong (methane aromatization)
Kenneth Toch (xylene isomerization)
Bart Vandegehuchte (long alkane
hydrocracking)
CaRE
40
questions?
41
rational ZSM-22 design
Bridge
site: far
pore mouths
Pore
mouth
site
micropores
external surface
(Pt clusters)
Bridge
site: near
100
Isomer Yield / mol%
80
60
40
20
0
423
473
523
Temperature / K
573
related patents:
- US20100181229
- US20110042267
publications:
- Hayasaka et al. Chem. Eur. J. (2007)
- Choudhury et al. J. Catal. (2012)
42
μkinetic engine: background
high-throughput
experimentation
microkinetic modeling
(includes all elementary steps)
1.
2.
optimize catalyst properties and
kinetic parameters
predict behavior for reactions /
compounds of the same family
• generic methodology
for kinetic model
construction
• no user intervention is
needed in
programming
• reaction network is
automatically
converted into rate
equations
43
μkinetic engine: workflow
Experimental
data
Reaction
Network
No. experiments
Input data
No. input variables Datafile
No. responses Generation
Reactor type
Initial values
Operating
conditions
Generate plots
Model predictions
Kinetic parameters
Statistical analysis of
results
Standalone software tool
44
detailed flow scheme
• start main program
• reading section
• overall information
• experimental
• regression
• reaction network
• thermochemistry
• regression section
• Rosenbrock
• LevenbergMarquardt
• adjust parameter
values
• perform simulation
for all experiments
• compare calculated
and experimental
outlet flow rates
• writing section
• simulation results
• statistical interpretation
no
yes
fit ok?
• thermochemical
calculations
• parameter
constraints
• solution set of
equations:
• initialization
• integration
45
calculated versus experimental values
Error
𝑁𝑒𝑥𝑝
𝑁𝑟𝑒𝑠
𝑆 𝛽𝑗 =
𝑤𝑖
𝑖=1
WSSQ
𝐹𝑖𝑙𝑐𝑎𝑙𝑐
−
exp 2
𝐹𝑖𝑙
𝛽𝑗
𝑚𝑖𝑛𝑖𝑚𝑢𝑚
𝑙=1
Weight to the
reponse
Experimental
flowrates
Flowrates
calculated using
model
Parameters
to be
estimated
46
solution set of equations: reactor model
• Plug Flow reactor (differential equations)
• Continuous Stirred Tank Reactor (algebraic equations)
𝐹𝑖𝑖𝑛 − 𝐹𝑖𝑜𝑢𝑡 + 𝑅𝑖 𝑤𝑐𝑎𝑡 = 0
47
solution set of equations: kinetic model
• net production rate of component i
Ri    i , j r j
j
where, αi,j is stoichiometric coefficient of
component i in reaction j
• reaction rate (A* + B  D*, A*: intermediate, B: response)
n
m
rs  ks presponse
intermediate
Ctot ,
ks  f (  j ),
s  1...nelem steps
j  1...nparameters
• rate coefficient
 Ea  1
1 
ks  kTave exp    

 R  T Tave  
β
48
solution set of equations
• Mass balance for the catalyst’s active sites
Ctot  C*  Cintermediate
• analytical solution only possible for simple reaction
mechanisms
• steady state approximation:
• intermediates are considered as highly reactive, i.e.,
net rate of formation equals zero:
Rintermediate  0
• DDASPK2.0 used as solver for the set of equations
49
graphical user interface
50
μkinetic engine: summary
• performs microkinetic
modeling adopting
complex networks in
heterogeneous catalysis
• no programming required
by the end user
• incorporates differential
and algebraic solvers +
deterministic & stochastic
optimization routines
• able to provide
information about quasiequillibruim steps.
51
μkinetic engine: summary
• reaction orders can also be
estimated
• no rate determining step.
• able to plot the agreement
between model and experimental
data points with residual error
and save them as images
• Provide statistical analysis of
results:
•
•
•
•
95% confidence interval,
t-value,
F value
etc.
52
transesterification
• ethylacetate + methanol over Lewatit
K1221 (sulphonic acid ion exchange resin)
+
+
E. Van de Steene et al. J. Mol. Catal. A-Chem. 359 (2012) 57-68
53
6th IDECAT/ERIC-JCAT Conference on Catalysis (IEJCat-6), 3rd-6th
March 2013, Brixen (Italy)
model discrimination
Simulated values (lines) exhibit a good agreement with the experimental results
(temperature effect and initial reactant molar ratio effect)
Kinetic model: ER_MeOH_SR: Eley-Rideal mechanism with the reaction of EtOAc from
the bulk with adsorbed MeOH on the catalyst surface as rate-determining step.


1
k SR K MeOH  aMeOH aEtOAc 
aMeOAc aEtOH 


K eq


r
1  aMeOH K MeOH  aEtOH K EtOH
54
6th IDECAT/ERIC-JCAT Conference on Catalysis (IEJCat-6), 3rd-6th
March 2013, Brixen (Italy)
model assessment: reaction mechanism
55

Microkinetics assisted design and optimization of catalytic reactions

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