Future Biorefinery Joint Research 2

Transcription

Ohjelmatunnukset
Programme Report 2011-2014
13
Ohjelmatunnukset
Programme Report 2011-2014
CONTENT
Foreword .........................................................................................................................................................5
World-leading knowledge platforms for wood-based biorefineries...........................................6
Introduction...................................................................................................................................................10
Modelling and techno-economic evaluation of biorefinery concepts.....................................14
New solutions for biomass fractionation ......................................................................................... 32
Ionic liquids for wood fractionation..................................................................................................... 52
Hydroxy acids (and other acids) from black liquor ........................................................................ 72
Biological effects of wood-based extracts and compounds in models of
human disease............................................................................................................................................88
Thermoplastic lignin and reinforcing cellulose fiber composites for advanced
biocomposite applications.................................................................................................................... 104
Biorefinery products ...............................................................................................................................122
Copyright Finnish Bioeconomy Cluster FIBIC 2014. All rights reserved.
This publication includes materials protected under copyright law, the copyright for which is held
by FIBIC or a third party. The materials appearing in publications may not be used for commercial
purposes. The contents of publications are the opinion of the writers and do not represent the official
position of FIBIC. FIBIC bears no responsibility for any possible damages arising from their use.
The original source must be mentioned when quoting from the materials.
ISBN 978-952-67969-6-3 (paperback)
ISBN 978-952-67969-7-0 (PDF)
Layout: Brand United Ltd
Printing: Kirjapaino Lönnberg
Coverpage: TOC graphic image from Parviainen, A., King, A. W. T., Mutikainen, I., Hummel, M., Selg,
C., Hauru, L. K. J., Sixta, H., Kilpeläinen, I.: Predicting cellulose solvating capabilities of acid base
conjugate ionic liquids. ChemSusChem. 2013. 6. 2161-2169. Copyright Wiley-VCH Verlag GmbH & Co.
KGaA. Reproduced with permission.
Page 32: Photo by Metla / Erkki Oksanen
FUBIO JR2 PROGRAMME REPORT
FOREWORD
The bioeconomy has fast developed as one of the most relevant platforms for
business and environmental sustainability today. In parallel, Finland’s centuries-rich
forest industry is undergoing radical renewal. Coupling leading-edge wood and paper
products expertise with milestone advances in technology, research competence
and knowledge, the industry is unlocking vast potential for new products and new
integrated processes – and turning its most ambitious targets and concepts into
realistic business opportunities.
Along with the renaissance of wood use in construction, design and mechanical
industry, environmentally friendly wood-derived chemicals are increasingly replacing
conventional oil-based materials. The wood raw material for chemical pulping contains
numerous components in addition to cellulose that are currently burned for energy
recovery. Intelligent process solutions drawing on new knowledge and Finland’s
common logistics, energy and technology platform are now enabling the separation
and generation of highly value-added products from this valuable bioresource. These
new products can be used to enhance existing paper and board products or applied in
new alternative business areas.
The forest industry has been the backbone of the Finnish economy throughout its
history. Today, the urgent need to find innovative applications for new forest-based
products is two-fold: the decline in the printing and writing paper sector and the fight
to find new sustainable business based on Finland’s staple renewable resource –
wood. The work done in the FuBio JR2 programme brings these efforts a significant
step forward by opening exciting development opportunities and lighting the path
towards innovative and sustainable industry renewal.
The five-year EUR 50 million FuBio JR2 programme, a continuation of FuBio 1,
represents a dedicated effort and investment by the Finnish Bioeconomy Cluster –
joint research company FIBIC Ltd. The programme lays a solid foundation for building
competence in bioeconomy research and for business creation. It also significantly
enhances networking between industry and the research community as well as joint
understanding of the research challenges and needs of the future.
Mika Hyrylä
UPM-Kymmene Oyj
Chairperson, FuBio Joint Research 2 Programme Management Group
5
WORLD-LEADING
KNOWLEDGE PLATFORMS
FOR WOOD-BASED
BIOREFINERIES
The renewal of the forest industry and creation of new businesses
are essential prerequisites for the future success of the Finnish pulp
and paper industry as part of a sustainable, bio-based economy.
In the second FuBio Joint Research programme,
have participated in the FuBio JR2 programme
companies
organizations
regard ionic liquids as extremely attractive
have jointly developed globally competitive
and promising, they admit that some aspects
knowledge platforms within the field of wood-
need more study and development before
based biorefinery research and development,
industrial-scale utilization.
and
research
by creating new value chains for refining novel
materials and chemicals.
The
FuBio
programmes
have
built
a
competence platform on ionic liquids and led to
A wide range of Finnish forest cluster
the creation of key research teams. However,
companies have actively participated in FuBio
new skills are still needed, and consequently
JR2. In the following chapters the companies
different consortia will launch more focused
highlight the results achieved in the programme.
programmes and projects in the near future,
to devise industrial applications.
Great new potential in ionic liquids
The development of new ionic liquids has
created great potential for new production
In the FuBio Joint Research programmes 1 and
processes in wood-based value chains. The
2 over 100 new ionic liquids were synthesized.
same knowledge is applicable to other areas
The best ones show great potential for
as well.
certain applications studied in another FIBIC
programme, FuBio Cellulose.
The FuBio JR 2 research work on ionic liquids
is expected to be invaluable for the future of
the Finnish forest industry and will probably
have a major impact for the renewal of the
Mikael Hannus, Stora Enso:
“Before we have industrial applications in use,
a lot of development work is needed. In general,
breakthrough technologies are not created
overnight and are developed at high risk.
biorefinery sector. Ionic liquids may even be a
The Fibic framework is a functional environment
game changer for future biorefineries.
for this kind of research and development.”
Although the majority of the companies that
6
Lignin and hemicellulose – raw materials
for future bio-based business
Several alternatives for bio-based
barrier materials
The research has given strong indications
The Fubio JR2 programme evaluated the
that residues from pulp and paper production,
applicability of several bio-based alternatives
such as lignin and hemicellulose, will have the
in
greatest impact in the production of novel bio-
xylan has been identified as one of the new
based products.
barrier materials with the greatest potential,
The Fubio JR2 programme has created new
insight into wood chemistry and promoted
barrier
applications.
Alkali-extracted
and its performance has been successfully
demonstrated at pilot scale.
broad competence in hemicellulose separation
As a barrier material xylan has many
technologies. Specifically it has improved
advantages: its bio-content is quite high, its
understanding of the phenomena of hot water
availability is good because the pulp and paper
extraction of hemicelluloses.
industry is the main supplier of the raw material,
The applications foreseen are now more realistic
and the production process is workable. The
than at the beginning of the programme.
end product has also been shown to have
However, the separation processes will become
promising converting properties.
more feasible when methods have been
The issues that still need to be solved are the
developed for the utilization of all possible
barrier capability against oxygen, and deeper
fractions.
cost calculations of the production process, as
One of the main research interests in
the FuBio JR2 programme was lignin and
well as detailed study on implementation in
industrial applications.
its potential as a component in bio-based
The programme helped in understanding
composites. The properties and production
the possibilities, but also the challenges, in
technologies of kraft lignin fibre composites
the use of biopolymers. At the same time, it
were studied, and the teams were capable of
created a framework for performing analyses.
developing and producing prototype products.
The demo trials performed by composite
manufacturers gave excellent feedback that
Pirkko Liias, Metsä Fibre:
can be utilized in further development.
“The bio-barrier study has generated knowhow
about the possibilities of different derivatives,
helping to decide which ones ought to be ruled
Kari Saari, Kemira:
out and which should be taken for further
“We regard new sustainable polymeric raw
development.”
materials, such as hemicellulose, as potential
future raw materials that can be substitutes for
fossil-based ones in use today.”
7
Networking created more value
The work goes on
In the work that studied ionic liquids, lignin
The research of the FuBio JR2 programme
composites,
was
bio-barriers,
mouldable
fibre
precommercial.
In
order
to
achieve
products, new filters or medicinal products,
industrial applications, further development
networking created more value than if the
work is needed. Many companies have already
research teams had been working alone. All
launched internal projects to continue the work.
in all, networking is a key attribute of all Fibic
programmes.
One of the participants noted that the best
outcomes were achieved in the teams that
worked openly and dynamically. Dialogue
The techno-commercial models created in
the programme broadened the scope of the
work with commercial viewpoints, and will act
as an excellent tool in further research.
Apart from pulp and paper companies,
between representatives of the research
several
and industrial partners has been extremely
in the programme. Through the FuBio JR2
technology
suppliers
participated
important for the successful results of the
knowledge platforms they have been able to
programme.
find suitable partners.
The programme was divided into work
packages, each with an industrial partner
Jussi Piira, Andritz:
represented in the steering group and in the
“The programme has provided us with an
technical meetings. This structure ensured that
outlook for future processes. The new processes
the programme was immediately focused in the
require intensive development of technologies,
right direction. In setting the study, important
which is why it is essential for a technology
issues such as regulatory compliance and
supplier to be part of the work as early as
scale-up of the processes were raised at an
possible.”
early stage.
Mika Hyrylä, UPM-Kymmene:
“The wide international and competent network
also made it possible to test end-products, such
as composites.”
8
INTRODUCTION
FuBio research was initiated in March 2009
with the launch of the first two-year joint
The Finnish forest industry has evolved
research programme. In 2011 FuBio was further
over
key
split into two separate programmes: ‘Products
phases, spanning from early tar production
from Dissolved Cellulose’ (FuBio Cellulose) and,
and sawmilling to modern pulp and paper
the focus of this programme report, ‘Future
making. Today, the production of wood-based
Biorefinery Joint Research 2’ (FuBio JR2).
the
centuries
through
several
chemicals – once a focal point of the industry
until its eclipse by low-cost, high-performing
At the time of planning the FuBio programme,
chemicals and materials of the petrochemical
national and international attention within the
boom – is seeing a resurgence. Biorefinery
field was almost exclusively focused on biofuels.
has now emerged as the next branch in the
It was therefore decided after careful analysis
evolution of end uses for Finland’s abundant
to exclude biofuels from the FuBio theme. The
forest biomass.
largest Finnish research efforts in biorefinery
at the time included the BioRefine programme
Future Biorefinery (FuBio) is one of the strategic
of the Finnish Funding Agency for Innovation
focus areas of the Finnish Bioeconomy Cluster
(Tekes) and various Technical Research Centre
FIBIC (formerly Forestcluster Ltd). The main
of Finland (VTT) programmes. These were also
objective of FuBio research is to establish
taken into account and relevant programme
in Finland globally competitive knowledge
interfaces were established.
platforms for the renewal of the existing forest
industry and the creation of new business. The
Creating new biorefinery value chains requires
FuBio research path is expected to create new
deep understanding of biomass structures. New
value chains in which biomass-based materials
processing technologies must be developed
and chemicals are used in substantial, global
hand-in-hand with the design of new biorefinery
markets. The potential markets of focus are
concepts, including their respective value chains.
both well-known to the forest industry (e.g.
Understanding the markets and having the
fibre-based packaging) as well as essentially
freedom to-operate in them are essential. The
new, such as textiles, nonwovens, polymers,
first steps towards future industrial partnerships
resins and thermo-formable composites.
must also be taken.
"The main objective of FuBio research is to establish
in Finland globally competitive knowledge platforms
for the renewal of the existing forest industry and the
creation of new business."
10
In addition to the main objectives defined
The globally competitive knowledge platforms
above, FuBio also aimed at achieving a broader
targeted by the programme, as mentioned
national impact by:
above, specifically include:
• Improving industry awareness of new wood
• New biomass fractionation methods,
biorefinery opportunities.
• Establishing new ways and levels of
cooperation within R&D in Finland.
• Shortening the time from idea to innovation
through effective collaboration.
• Establishing strategic, international R&D
partnerships.
• Maintaining and improving Finnish
biorefinery R&D facilities through lab and
early-stage piloting/initial material demos.
• Educating a new generation of researchers
(M.Sc. and D.Sc./PhD) for the biorefinery field.
especially based on ionic liquids and hot
water extraction,
• Advanced separation technologies suitable
for separation of biomass fractions as well
as hydroxy acids from black liquor,
• Chemical and biotechnical modification/
up-grading of biomass fractions to natural
polymers, extractives, hydroxy acids, etc.,
• Application of wood fractions as structural
composites, hydroxy acid products, new
board packaging concepts, reactive/active
filter materials and health applications,
• Modelling, especially techno-economical
The scientific publication output of the FuBio
evaluation of immature biorefinery concepts,
programme has increased as a result of
• Biomass characterization and analysis, and
FuBio JR2, bringing greater global visibility
• Initial process piloting and/or material
for the programme and promoting the open
prototype production
innovation strategy chosen for FuBio.
As a summary, Figure 1 shows the key
application areas of the FuBio research theme.
Figure 1. The six target markets of FuBio. Regenerated fibre and chemicals was targeted by the FuBio
Cellulose programme, the remaining markets by FuBio JR2.
11
Programme portfolio
groups together with the industrial tutors
assisted the WP leaders in focussing the work
FuBio JR2 was divided into eight Work Packages
as needed.
(WPs). The use of wood fractionation alongside
a pulp mill (WP1 Hot water extraction) or even
to replace a pulp mill (WP2 Novel biomass
The Management Group had the following
fractionation) was examined. Possible future
members:
products were identified in the area of advanced
biocomposites (WP3), packaging (WP4), filters
(WP4) and health applications (WP5) as well as
• Mika Hyrylä, UPM, Chairman (Eeva
Jernström until December 2012)
for hydroxy acids separated from black liquor
• Mikael Hannus, Stora Enso
(WP6). In modelling and piloting (WP7) the focus
• Johannes Heiskanen, Novoplastik
was targeted at improving models for new
• Seppo Hiljanen, Valmet
processes and techno-economical evaluation
• Annaleena Kokko, VTT (Niklas von Weymarn
of selected FuBio product cases. The main
goals and results of the work packages are
presented in the following chapters.
until August 2012), Programme Manager
• Markku Leskelä, FIBIC (Lars Gädda until
April 2012)
• Pirkko Liias, Metsä Fibre
• Risto Lilleberg, Metsäliitto Group
Management of the programme
• Erkki Peltonen, Myllykoski (until September
2011)
The
a
FuBio
JR2
Management
programme
Group
was
(MG)
led
by
including
• Jussi Piira, Andritz (Paterson McKeough
until May 2013)
representatives from industry and academia.
• Kari Saari, Kemira
The main responsibility for day-to-day execution
• Lauri Verkasalo, Metsä Board (Ari Kiviranta
was with the Programme Manager (PM). Each
work package had a WP Leader and one or
until September 2011)
• Stefan Willför, Åbo Akademi University,
several Industrial Tutors. The industrial tutors’
Scientific Coordinator
role was to bring an industrial perspective to
• Erja Ämmälahti, Tekes
the work packages, while the WP leaders were
responsible for day-to-day management of
Dissemination of the FuBio JR2 programme
the WP. The work packages were divided into
results has been achieved through a variety of
tasks and subtasks, and some of the tasks were
channels. The main channel for the distribution
assigned specific Task Leaders. The PM and WP
of results, reports and meeting minutes has
leaders formed the execution Core Team.
been the FIBIC research portal, accessible to
FuBio JR2 programme partners, and the FIBIC
12
The main task of the management group was to
website (http://fibic.fi/programmes/fubio-jr2-2).
supervise the progress of the programme with
Additionally, results have been extensively
respect to the objectives and the programme
shared in both external (public) and internal
plan. The management group followed the
seminars, and demonstration samples and
work progress of specified issues through a
related posters have been displayed at SHOK
gate system and WP results and achievements
(Finnish strategic centres for science, technology
through WP presentations in management
and innovation) summits and Tekes events, as
meetings and through Programme Milestones
well as in programme overviews presented at
and Deliverable reports. The WP steering
FIBIC seminars and international conferences.
Participants and international
cooperation
The
programme
participants
have
also
actively presented the programme results
in international conferences, COST action
The three-year joint research programme on
meetings
future biorefinery had a total of 22 industrial
seminars have also been arranged by the
and
workshops.
International
and research partners, bringing multi-faceted
programme, especially in WP2 in the area of
knowledge and competence to the programme.
ionic liquids, which attracted high international
interest and was highly commended by the
programme partners. In order to demonstrate
Industrial partners:
the increased competence resulting from
the programme the main results have been
• Andritz
published in peer-reviewed journals, with
• FIBIC
over 80 publications to date and close to 40
• Kemira
currently submitted for publication. Over 20
• Metsäliitto Group
Master’s theses and five PhD thesis have been
• Metsä Fibre
written by students fully or partly financed
• Metsä Board
by FuBio programmes, with a further 10 PhD
• Myllykoski
students expected to defend their thesis
• Novoplastik
within the coming year.
• Stora Enso
• UPM-Kymmene
• Valmet
Research partners:
• Aalto University
• Lappeenranta University of Technology
• Finnish Forest Research Institute, Metla
• Tampere University of Technology
• University of Helsinki
• University of Jyväskylä
• University of Tampere
• University of Turku
• University of Oulu
• VTT Technical Research Centre of Finland
• Åbo Akademi University
International cooperation in Future Biorefinery
Joint Research 2 was achieved through
researcher exchange, with more than 15
researchers visiting over a dozen universities
and research institutes in Portugal, Venezuela,
Sweden, Spain, France, Germany and Austria
for more than 40 person-months.
13
MODELLING AND
TECHNO-ECONOMIC
EVALUATION OF
BIOREFINERY
CONCEPTS
CONTACT PERSON – Work Package 7 leader Eemeli Hytönen, [email protected]
Aalto University: Moshood Abdulwahab, Waqar Ahmad, Ville Alopaeus, Kaj Jakobsson,
Susanna Kuitunen, Zheng Liu, Kaarlo Nieminen, Juha Visuri
Andritz: Paterson McKeough
GloCell: Jari Aittakari, Hanna Kalanne, Juhani Lehtonen, Pirita Mikkanen, Jukka Seppänen
Kemira: Marcus Lillandt, Anna-Maija Saariaho
Lappeenranta University of Technology: Mari Kallioinen, Elsi Koivula, Jarno Kohonen,
Maaret Paakkunainen, Satu-Pia Reinikainen
Metsä Fibre: Esko Turunen
Pöyry Management Consulting: Carina Björnström, Henna Jääskeläinen, Jesse Kautto,
Anna Saarentaus, Katja Salmenkivi, Juulia Rouhiainen, Petri Vasara
Stora Enso: Kalle Ekman
University of Oulu: Eva Pongracz, Paula Saavalainen
UPM-Kymmene: Mika Hyrylä, Seppo Virtanen
Valmet: Seppo Hiljanen, Päivi Uusitalo
VTT Technical Research Centre of Finland: Tuomas Helin, Catharina Hohenthal, Timo Kaljunen,
Marjo Kauppi, Marjatta Kleen, Vesa Kunnari, Juha Leppävuori, Marja Nappa, Lotta Sorsamäki
14
ABSTRACT
In Future Biorefinery Joint Research 2 (FuBio JR2), modelling was used at different levels
of biorefinery technology development to support research and to indicate the industrial
feasibility of the novel technologies developed in the programme. The focus was on i)
phenomena-based modelling and statistical experimental design of hot water extraction
of hemicelluloses from wood, ii) early-stage techno-economic modelling of future
biorefinery concepts based on the wood fractionation technologies and novel biorefinery
products developed in the programme, and iii) process modelling and simulation, and
quantitative economic and qualitative opportunity analysis of selected promising future
biorefinery concepts.
Two new models were developed for pressurized hot water extraction (PHWE). The
new models are more advanced and comprehensive than the previous PHWE models
presented in the literature, enabling more detailed analysis of the phenomena involved
and optimization of the process.
Several process concepts were designed and evaluated. Conceptual-level technoeconomic screening of some 100 concepts as well as more detailed modelling of five
process and product development ideas, including hot water extraction, ionic liquids
wood fractionation, black liquor hydroxy acids separation, bio-barriers and biocomposites, were conducted. New methods for process integration, market entry and
comprehensive risk assessment were also developed and successfully demonstrated
along with the evaluation of several selected concepts in detail. The work was done in
close collaboration with research and industry partners.
Keywords:
biorefinery concepts, modelling, physico-chemical modelling, techno-economic modelling
15
1. Background
2. Objective
Different knowledge and data are needed at
The overall objective of the modelling work was
different
stages.
to provide more knowledge and data on the
For example, initial concept analysis requires
technologies developed in the programme in
a systematic approach and modelling of
order to support decision making.
technology
development
overall production systems, but no detailed
data is needed on the process conditions or
The specific goals set for physico-chemical
phenomena involved in the different processing
modelling were: 1) develop chip and reactor scale
steps. In contrast, when scaling up a process
models for pressurized hot water extraction
step and designing its process and process
(PHWE), and 2) develop a comprehensive
equipment, understanding of the specific
model for PHWE chemistry (especially model
phenomena involved in that step in the process
the evolution of the hemicelluloses’ molecular
is needed, whereas modelling of the overall
weight distribution).
production system is not necessarily required.
Therefore the problem statement and scope
The specific goals set for techno-economic
of modelling varies significantly during the
modelling were: 1) to create new biorefinery
technology development.
concepts and evaluate their sustainability, and
2) to develop modelling tools and apply them
Many modelling methods and tools related to
to support the technology development work.
the fields of research of the Future Biorefinery
Joint Research 2 programme have been
previously developed. For example, a number
3. Research Approach
of existing chemical process design methods
and simulation tools are applicable to the FuBio
JR2 context and these have been combined
3.1 Physico-chemical modelling of hot
water extraction
in earlier FIBIC programmes as a toolbox for
quantitative and qualitative concept evaluation
Chip and reactor scale modelling of PHWE
for
addition,
For the modelling of simplified PHWE chemistry
simulation tools for modelling pulping and
for chip and reactor model development,
bleaching physico-chemical phenomena have
experimental data from PHWE of coarse birch
also been developed. These state-of-the-art
(Betula pendula) sawdust in a batch reactor
tools required further modifications to meet the
was collected. A high liquid-to-wood ratio
targets of the current programme.
was selected to minimize limitations on the
aiding
decision
making.
In
solubility of the extracted wood components.
Various process and product ideas were
Experiments were conducted at different
studied and developed in FuBio JR2. To steer
temperatures and with different durations.
future research efforts and estimate the future
After each experiment the wood residue was
business potential of these pre-commercial
collected from the reactor and the yield of
stage R&D ideas, production concepts were
the components was measured. Based on
designed, screened and evaluated and tools
this data the appropriate stoichiometry and
for modelling the phenomena taking place in
kinetic parameters of the reactions leading
the studied wood fractionation processes were
to delignification and condensation of lignin
developed.
as well as carbohydrate degradation were
estimated. A model combining the reaction
16
kinetics with the diffusion in a wood particle
A high-order numerical method capable of
was constructed in Matlab. The differential
extremely accurate prediction of integral
equation associated with the model was solved
properties of the distribution is applied. Other
numerically using the finite difference method
parameters
and the PDE tools available in Matlab. The
parameters of the components included in
model enables a simulation of the reaction
the modelling of hot water extraction are then
product evolution at chip level during PHWE.
estimated and gathered from public sources.
related
to
physico-chemical
Comsol Multiphysics was chosen for simulating
the progress of PHWE at the reactor level, as
The aim was to collect as many as possible
the software includes tools for describing flow
models and parameters from the literature.
and heat transfer in porous media and enables
Some of the model parameters were regressed
equations for the reaction kinetics to be added.
using literature and experimental results of the
programme research.
Comprehensive modelling of PHWE chemistry
In order to be able to build the physico-
3.2 Techno-economic modelling
chemical model, understanding was needed
of which properties and chemical constituents
The overall techno-economic modelling approach
of wood are relevant to the modelling of hot
used in the programme is illustrated in Figure 1.
water extraction as well as how the chemical
constituents react and dissolve from wood into
To support R&D and to provide preliminary
the extract in hot water extraction conditions.
techno-economic performance information for
Both lignin and carbohydrate reactions are
industry regarding the processes and products
considered and, since several reactions are
developed in the programme, various process
catalysed by hydrogen ions, special attention is
concepts were created, designed, and evaluated
paid to accurate modelling of pH evolution.
in the screening phase. A method for this earlystage concept screening was developed. The
In the modelling, changes in the molecular
method exploits early-stage process design
weight
hemicellulose
methods to obtain comparable results for the
polymers are considered by describing chain
different overall production systems that are
lengths as discrete size categories where the
possible for a given concept. The method is
rate of change of number concentrations for
illustrated in Figure 2. Prices of all raw materials,
various polymer chain lengths is calculated.
chemicals, utilities, and the different factors
distribution
of
the
Figure 1. Overall techno-economic analysis approach.
17
Figure 2. Light techno-economic analysis method developed for concept screening.
used for fixed cost assessment were agreed,
recycling of the reaction media and catalysts. If
and the concepts were created together with
enough data was not available, short-cut models
the project partners. For capital cost estimation,
and assumptions were used. Preliminary variable
methods developed by Bridgewater and Zevnik
production costs were assessed for sensitivity
& Buchanan 1 were used.
analysis
purposes.
The
resulting
process
descriptions and balances were further used in
In screening, concepts were developed from
quantitative economic analysis and qualitative
R&D ideas by specifying targeted end products,
modelling of the cases.
feedstocks,
design
capacities,
process
integration opportunities and main process
Net Present Value (NPV) and Return on
parameters. Variable and fixed production
Investment (ROI) were the main quantitative
costs were calculated using parametric models
feasibility analysis instruments used to evaluate
and input-output material and energy balances.
the economic feasibility of the cases. An
enhanced probability simulation tool was used
Based on the results of the screening and the
in the analysis to forecast the probabilities
progress of the research, together with project
of achieving positive outcomes for NPV and
partners conceptual designs for five cases were
ROI. This method was chosen because the
developed. Process modelling was then conducted
probability of a given outcome can often be more
for these designs: block-flow diagrams were
informative than the actual figures themselves,
designed or further refined from those designed
especially at the early development stage.
in the screening phase, and mass and energy
balances were modelled using process simulation.
In the qualitative opportunity assessment
The simulation models were parameterized using
many variables were assessed. The variables
experimental research results, partners’ expertise
were divided into two categories: internal and
and literature. If pulp mill integration was part of
external. The variables were evaluated on a
the concept, the interface between the processes
scale from 2 (high) to low (0) opportunity. In
was defined and pulp mill impacts were simulated
addition, different weight factors were given
using a steady-state process simulation model of
to the variables, reflecting their relative
the entire system. A pulp mill model developed in
importance. External variables in the analysis
the EffFibre programme was used. The technical
mainly included market-related factors such as
analysis focused on the main process (production
market size and growth. Economic feasibility
and purification of the main product), and
was also a key external variable. Internal
variables, in turn, mainly included technical
18
1 e.g. Holland, F.A. & Wilkinson, J.K. Perry's Chemical Engineers'
variables such as technical feasibility, product
Handbook, section 9 (Process Economics), McGraw-Hill, 1999
quality feasibility and technical availability.
4. Results
level and reactor level, respectively. The Matlab
program calculates the time development of
4.1 Physico-chemical modelling of hot
water extraction
the 3D distribution over the wood chip of the
various reaction products of lignin, xylan and
glucan. It is possible to alter the size of the
Chip and reactor scale modelling of PHWE
chip, the cooking time and the temperature in
As an example reaction definition, Figure 3
the simulation. Likewise, the Comsol program
shows the reaction scheme for xylan. The data
simulates the product distributions in the
from the experimental treatments indicate that
reactor. The geometry and heating circulation
there are two sub-components of xylan (XN1
of the simulated reactor can be changed, as can
and XN2) with different reaction rate constants
the porosity and permeability of the chip bed.
for degradation into oligosaccharides (XOS).
The main results of the modelling of hot water
The temperature dependency of the reaction
extraction were increased knowledge of the
rates is assumed to follow the Arrhenius equation.
phenomena taking place in the system, and the
Table 1 shows the related pre-exponential
simulation tool that can be used in further hot
(frequency) factors and activation energies.
water extraction research.
A similar reaction scheme was developed
Comprehensive modelling of PHWE chemistry
for
In
that
The comprehensive PHWE chemistry modelling
degrades
into
work provides interesting insights into the phe-
hydroxymethylfurfural (HMF). A Matlab program
nomena taking place during PHWE. A schematic
and a Comsol multiphysics program, based
illustration of the various phenomena and reac-
on estimated reaction rates and values for
tions included in the model is shown in Figure 4.
case,
the
degradation
the
of
monosaccharide
glucan.
physical parameters describing diffusion in the
wood particle and flow in the porous medium,
Considering the onset of the PHWE reactions,
were constructed to simulate PHWE at chip
the uronic acids seem to be responsible for
Figure 3. Reaction pathways for xylan in PHWE. Notation: XN1 – fast-degrading xylan, XN2 – slowly
degrading xylan, XOS – xylo-oligosaccharides, X – xylose, F – furfural, DP1,DP2 – unspecified low molecular
weight degradation products, ki – reaction rate constant.
Table 1. Pre-exponential factors (A) and activation energies (Ea) for xylan reactions.
k1
A (min )
3.12 ∙ 10
Ea (kJ mol-1)
161.04
-1
k2
17
7.28 ∙ 10
179.54
k3
17
6.58 ∙ 10
127.94
k4
12
3.08 ∙ 10
129.91
k5
12
5.13 ∙ 1016
168.52
19
introducing hydrogen ions into the fibre-bound
bre wall, the uronic acids also dissolve. Dissolv-
liquid, which, when the temperature is raised,
ing uronic acids weaken the ion exchange phe-
begin catalysing various reactions such as
nomena, and metal ions are also able to move
deacetylation and hemicellulose degradation.
to the external liquid phase as they are no long-
Metal ions, naturally present in the fibre
er held in the fibre-bound liquid as counter ions
wall, neutralize part of the acidity. In order to
for the dissociated uronic acids. Besides acetic
accurately estimate the initial hydrogen ion
acid, uronic acids and metal ions seem to have
concentration in the fibre wall liquid, it is crucial
a significant influence on the evolution of pH in
to know the amounts of all chemical compounds
the external liquid phase.
influencing pH. According to our current
understanding, it seems that uronic acids and
Understanding the behaviour of pH during hot
metal ions are the most relevant compounds.
water extraction is essential because hydrogen
Although, based on our modelling results and
ions catalyse cleavage of the glycosidic bonds,
some evidence provided in the literature, the
thus shortening the hemicellulose polymers.
fibre-bound liquid is acidic, the water external
Besides predicting the evolution of pH, another
to the wood particles is close to neutral pH.
novelty of the model is its capability to predict
The ion exchange, i.e. the unevenness of the
the evolution of the hemicelluloses’ molecular
electrolyte composition, in these two liquid
weight distribution during hot water extraction.
phases (fibre-bound and external liquid phase)
Furthermore, monomer and other oligomer
was modelled using Donnan theory, which is
concentrations
widely used and acknowledged in the context
feature facilitates the optimization of hot water
of pulp bleaching and, for example, in studying
extraction performance with respect to various
semipermeable membranes.
end products. The amounts of dissolved lignin
are
also
reproduced.
This
and furfural, which are potentially problematic
As hemicelluloses start to dissolve from the fi-
for the process, are also predicted by the model.
Figure 4. Schematic of the phenomena included in the comprehensive hot water extraction model.
20
The chemistry model for PHWE can be
used together with the chip and continuous
4.2 Early-stage techno-economic modelling
of concepts based on research ideas
digester models developed in the EffFibre/VIC
project. Furthermore, a flow-through reactor
Over 100 ideas were evaluated using the method
model using a simplified chemistry model
illustrated in Figure 2 (see Table 2 for aspects
was also developed. In the chemistry model,
varied and combined). The concepts and overall
only the cleavage of the glycosidic bonds in
systems were defined based on discussions
hemicelluloses was considered. The chemistry
with researchers and industry representatives.
model also reproduces the molecular weight
distributions of the extracted hemicelluloses.
Based on the early-stage techno-economic
modelling of all of the process and overall system
The developed model enables a priori simulations
ideas, the most promising future biorefinery
of the effect of different buffers and additives on
concepts were selected by the industrial
pH evolution. Thus, screening work concerning
partners for further detailed modelling.
optimal
conditions,
such
as
particle
size,
additives, liquid-to-wood ratio, temperature and
duration, can be done with the simulation model.
4.3 Quantitative and qualitative
modelling of selected Future Biorefinery
concepts
From the academic point-of-view, this kind of
phenomena-based modelling enables testing
Five promising overall production systems based
of different theories in a quantitative manner
on the programme’s technology development
and reveals shortcomings in the present
ideas were identified and evaluated:
theories. For industry, the model can be used in
process optimization and development.
1) Hot water extraction of high molecular
Table 2. Evaluated concepts from FuBio JR2 process and product development.
Research topic
Examples of concepts
Pressurized hot water
extraction (PHWE)
PHWE at a sawmill, kraft pulp mill, TMP plant, or CTMP/soda plant.
Extraction of high or low molecular weight hemicelluloses.
Extraction of sawdust or chips.
Ionic liquids
Kraft pulp to acetate-grade dissolving pulp.
Wood to TMP-like pulp.
Wood to kraft-like pulp.
Composites
Internally, externally or unmodified (using internal plasticization, chemicals, enzymes).
Different lignin-fibre-plasticizer ratios.
Barriers
PHWE-xylan, modification of GGM, TOFA hybrid polymers, fatty acid cellulose esters, reactive milling, cellulose-polymer blends.
Hydroxy acids (HA)
HA separation technologies (separate & combined): a) Electrodialysis, b)
Ion-exchange, c) Chromatography, d) Acidification, e) Cooling crystallization.
Products: a) Hot glues, b) Chelating agents.
Future biorefineries
Combinations of the above-listed concepts integrated into the forest industry supply chain.
21
weight (MW) hemicellulose from sawdust, 2)
Two scenarios were evaluated, in which the
Separation of hydroxy acids from kraft black
extraction yield and extract dry content were
liquor, 3) Biocomposites, 4) Biobarriers, and 5)
varied (Table 3).
Future sawdust biorefinery based on hot water
extraction.
The mass and energy balances and the
preliminary dimensioning data for the equipment
Case 1 – Hot water extraction of high MW
were used in quantitative economic analysis, in
hemicellulose from sawdust
which it was clearly seen that the production
Figure 5 illustrates the process concept and
costs for the material were high, more than
the main process parameters and balances for
double the price of competing materials. One
extracting high molecular weight hemicelluloses
major reason for the high costs is the small
from spruce sawdust. The production scale was
design capacity which results in high fixed costs
defined based on sawdust availability in Finnish
(e.g. personnel and capital costs)
sawmills. The process conditions (temperature,
pressure, solid:liquid ratio, flux) and efficiencies
The process is considered to be relatively mature
(extraction yield, separation and purification
(suitable process equipment exists); however, the
efficiencies) were based on experimental
overall concept would require further refinement.
results. The balances were simulated using the
For example, the yield based on the experimental
Balas® process simulator.
work of the programme at the time of conducting
the study was very low. Moreover, the end product
(extract) is not pure high-MW hemicellulose and
might not be suitable for high-value applications
without further processing.
Figure 5. Block-flow diagram of Case 1: High MW hemicellulose extraction from sawdust.
Table 3. Scenario definition for high MW hemicellulose extraction.
Raw extract yield (= dissolved sawdust
Base case
Optimistic case
Unit
2
10
% on dry
1.1
5.0
fraction led to membrane)
Dry content of extract
22
sawdust
%
Case 2 – Separation of hydroxy acids from
The results of modelling the four scenarios
kraft black liquor
were used in quantitative and qualitative
From the 12 alternative hydroxy acid separation
evaluation of the case. The economics seem
process
systems
highly promising if acids production is targeted
(alternatives listed in Table 2), two were chosen
exclusively at glue production, compared to the
by the industrial partners for detailed analysis.
option of using part of the acids production as
In these two overall systems, the product
chelating agent. However, although the product
would be either a mixture of all hydroxy acids,
price is quite low, the product quality currently
or two mixtures, a high and a low molecular
remains somewhat uncertain.
concepts
and
overall
weight mixture targeted at hot glue or hot glue
and chelating agent applications, respectively.
As process technologies, all of the considered
The process concept included two alternatives,
process steps are mature in different contexts.
which utilized different technology for liberation
However, processing of kraft black liquor using
of acids from their salt form: ion exchange (IEX)
these
or electrodialysis (ED). The process concept is
graphic separation, ion exchange, electrodialysis)
illustrated in Figure 6.
has been done only at laboratory scale and
separation
technologies
(chromato-
therefore further technology development is
The main assumptions for the case evaluation
needed. Furthermore, impacts on the pulp mill
were:
chemical recovery cycle (Na/S balance) should
be minimized and products’ applicability further
• Pulp mill production capacity 700 000 adt/a
evaluated. Thus, the overall concept still needs
• Hydroxy acids production rate
development.
- 1/3rd of pulp mill black liquor processed
and 15% yield of HA -> production 35 000t/a
- Volatile (formic and acetic) acids yield 7%
of pulping raw material
• H2S handling and volatile acids recovery
excluded
Case 3 – Biocomposites
A total of 26 overall biocomposite production
systems were analysed using light technoeconomic analysis. Of these, two were selected
for
more
detailed
evaluation:
lignin-fibre
• Pulp mill integration
composite without (Figure 7 a) and with internal
- Evaluated using WinGems pulp mill model
lignin plasticization (Figure 7 b).
developed in the EffFibre programme
- Cooking variables (effective alkali and
The recipes were based on experimental results
sulfidity) kept constant by NaOH makeup
and optimization for targeted end product
and fly ash purge
properties (composite mechanical properties):
Figure 6. Block-flow diagram of Case 2: Hydroxy acids separation from kraft black liquor.
23
lignin content 36% and 41%, and fibre
Case 4 – Biobarriers
content 30% and 20% for the two concepts
Two alternative concepts were also selected
respectively; the remainder of the composite
for detailed analysis of biobarrier production
pellet was plasticizer. Internal plasticization
based on light techno-economic analysis
was assumed to be done using purchased
and technology development. The two very
acetic acid anhydride, and the excess acetic
different
acid that is recovered after plasticization was
production of hydroxypropylated xylan based
assumed to be sold.
and cellulose co-polymer based barriers in
concepts
considered
were
the
fast-food packaging. The process block flow
Process
equipment
for
the
composite
diagrams are illustrated in Figure 8.
production exists, and the composite properties
can be further developed/targeted and the
In the hydroxypropylated xylan (HPX) case,
most suitable applications found to develop the
xylan extraction from kraft pulp is included in
overall concept.
the concept to enable efficient alkali recycling.
Separation and purification process parameters
The process without internal plasticization is
were based on literature and partner input.
simpler and showed better feasibility, but as the
composite price range used in the analysis is
The cellulose co-polymer case was based on
wide, product quality will ultimately determine
the research partner’s definition and literature
the price. Therefore, if internal plasticization
process parameters.
enhances the properties, the economics can
absorb the cost of internal plasticization. Acetic
The cellulose co-polymer product consists
acid as a side-product also has a significant
mainly of inorganic compounds (sodium and
impact on the overall feasibility.
zinc) and its suitability for food packaging
a)
b)
Figure 7. Block-flow diagram of Case 3: Composite concepts: a) no modification of raw materials, b)
internal plasticization of lignin.
24
applications thus needs careful examination. On
Case 5 – Future sawdust biorefinery based on
the other hand, in the hydroxypropylated xylan
hot water extraction
case the impacts on kraft pulp properties should
The fifth case was constructed around several
be evaluated and possible further valorisation
project focus areas:
of the pulp after xylan extraction to dissolving
pulp considered instead of selling it as kraft pulp.
• Hot water extraction of hemicelluloses from
Therefore, in both cases, further technology and
sawdust to produce high and lower MW
concept development is needed.
fractions; use of the high MW fraction for
barrier production.
As the economic feasibility of both cases is
• Kraft cooking of the extraction residue to
dependent on coating layer costs, cost per
obtain black liquor and pulp; separation
area is more critical than cost per tonne. Figure
of lignin from the black liquor, e.g., for
9 shows how the probability of a positive ROI
composite production; use of the pulp as
changes as a function of layer cost (c/m2) with
fibre for composites, or oxygen delignified
different layer amounts.
and bleached as pulp.
a)
b)
Figure 8. Block-flow diagram of Case 4: Barrier concepts: a) hydroxypropylated xylan, b) cellulose polymer
blend.
25
Figure 9. Probability of a positive ROI in the studied barrier cases with different coating amounts as a
function of coating layer material costs (cent/m2). Cepe: cellulose co-polymer; HPX: hydroxypropylated
xylan. Reference material cost illustrated on x-axis: PE&PP – polyethylene & polypropylene, PET –
polyethylene terephthalate, PA – polyamide.
The concept is illustrated in Figure 10.
The concept was modelled using the Balas®
process simulator and the integration impacts
The main assumptions of the case were:
were simulated using the WinGems pulp mill
model developed in the EffFibre programme.
• 100 000 or 20 000bdt/a sawdust
The main integration impacts for 20 000bdt
• Process integrated into a kraft pulp mill
sawdust/a capacity would be:
(600 000 t/a)
• Washed pulp to oxygen delignification stage
of the kraft pulp mill
• Pulp from sawdust cooking increases pulp
production by 1.5%
Figure 10. Block-flow diagram of Case 5: FuBio concept with hypothetical production capacity.
26
• 1.5% higher fibre line capacity required
downstream from oxygen delignification
• 1.4% increased white liquor demand
Summary
The cost breakdown of the evaluated cases
varies somewhat, as illustrated in Figure 11.
• 2.2% increased evaporation requirement at
evaporation plant
The difference in cost distribution results partly
• Decreased net electricity production
from the selected modelling scope (e.g. whether
• Increased fly ash purge
the feedstock has a purchase cost or not), the
scale of production, and the processing type
Four products are generated: two streams of
(e.g. whether chemicals are needed or not).
extracted hemicellulose, sawdust-based pulp,
These results should not be used to compare
and lignin separated from the black liquor. The
economic feasibility between cases, as they
raw material for the process is sawdust. In
only indicate the relative cost distribution.
this case, the sawdust cost is essential to the
A preliminary cross-case comparison can,
economic feasibility of the case.
however, be made between cases 1 and 5 where
PHWE was considered to be one of the main
The overall system requires further development
technologies: with higher hemicellulose yield
and, due to its small design capacity, process
the share of fixed costs decreases (feedstock
simplifications may be needed, e.g., related
flow nearly the same in these cases) while, on
to lignin separation. The clearly improved
the other hand, the added lignin separation
extraction yields and better selectivity in
process requires chemicals.
purification compared to Case 1 obtained at the
laboratory scale indicate good potential, but the
final use of the other fractions requires further
development.
Figure 11. Operating cost breakdown of the analysed cases
27
Figure 12 shows the qualitative analysis results
based on the present economic evaluation
5. Exploitation and impact of
results
and assessment of other qualitative analysis
variables. Based on their total scores, the
The
studied cases were plotted (x-axis: sum of
knowledge developed focusing on hot water
internal variables; y-axis: sum of external
extraction phenomena, purification of the hot
variables)
with
the
level
of
modelling
methods
and
tools
and
opportunity
water extract, and the sustainability of the
increasing from left to right (x-axis) and
different process concepts and value chains
upwards (y-axis).
provides crucial new information for industry
decision
Comparing the cases, the level of opportunity
making
and
for
steering
future
research.
was found to be highest in external (marketrelated) terms for the separation of hydroxy
The thorough modelling of PHWE was based
acids
on combined knowledge of aqueous phase
from
black
liquor
and
for
lignin
composites. In these two cases, technical
thermodynamics,
challenges related to operation and product
kinetics, and mass transfer. The resulting
quality were, however, found. Technically, the
model can be used in optimization of PHWE
most promising cases were found to be two
conditions to produce either sugars or high
cases based on hemicellulose fractionation:
molecular
weight
ion
exchange,
hemicelluloses,
reaction
and
for
barrier films based on extraction of xylan from
bleached pulp, and hot water extraction of
hemicelluloses from sawdust and subsequent
sawdust cooking. However, these cases scored
relatively low in market-related terms.
Conclusions, risks and suggestions for each of
the five cases are listed in Table 4.
Fubio Opportunity Evaluation
High
Case 1 – Hot water extraction of high MW hemicellulose from sawdust
Case 2 – Separation of hydroxy acids from Kraft black liqour
External
Case 3 – Biocomposites
Case 4 – Biobarriers
Case 5 – Future sawdust biorefinery based on hot water extraction
Low
Low
Internal
High
Figure 12. Qualitative opportunity assessment of the studied Fubio JR2 cases.
28
Table 4. Summary of case evaluations.
Case Conclusion
Highest risks
Suggestions
1
• Technical and economic feasibility
• Target concepts where the cellulose/
• New concept that could generate
additional revenue for a sawmill.
• Very small production rates and poor
(ROI negative in all cases; labour and
lignin fraction has an end-use of
capital costs significant).
higher added value (compared to
economic potential.
energy use) and hot water extraction
is needed to achieve this.
• Step-wise extraction with multiple
end products could be another
interesting concept (poly-, oligo- and
mono-based).
2
• Target product markets are expected
to grow annually 4-6%
• Look for alternative ion-exchange
work has been carried out with
system cleaning (organic acid based,
soda black liquor, the separation
or circulation based) to replace the
concept could have >10% IRR with a
processes have not been piloted
high H2SO4 demand (and to remove
product value of 1000 €/bdt.
using black liquor long enough to get
high cost of chemicals and fly ash
• Electrodialysis-based production
• Both production routes and product
alternatives seem to have positive as
data, e.g., on fouling & cleaning.
• Product quality – application
well as negative environmental and
testing has not been carried out
social impacts based on preliminary
using obtained acid mixtures as
analyses.
3
• Technical feasibility – experimental
• Target market is ~2Mt/a with
of both composite types should be
prices are high on average.
tested in the application to verify
have very good economic return
melt and chelating agent).
feedstocks.
• Product quality – strength properties
expected growth of over 5% CAGR;
• Unmodified lignin case seems to
disposal).
• Conduct further product testing (hot
their performance.
• Technical aspect – relatively large
and internal plasticization case
share of the product is plasticizer,
has potential assuming the quality
which is potentially produced from
improvement obtained from
food-grade feedstock.
• Conduct further product testing in
target application.
• Investigate other possible
plasticizers and/or the possibility to
decrease its share in the composite.
plasticization is worth over 500 €/t.
4
• The target market is ~ 1Mt/a (Global)
• Product quality – Cellulose co-
• Study the compatibility of the barrier
and 0.4Mt/a (Europe), considering
polymer product consists mainly
in combinations of different barrier
large fast-food chains. Annual volume
of inorganic compounds (sodium
materials (oxygen, water vapour
growth expected to be about 5%.
and zinc) and the suitability in food
• Cellulose co-polymer case seems to
packaging application needs careful
have good economic return due to
very good properties with thin layer
and relatively simple process.
• Hydroxypropylated xylan case
inspection.
• Technical aspect – in
hydroxypropylated xylan case the
barriers).
• In hydroxypropylated xylan case,
integrated concept with added
value cellulose product should be
considered.
xylan extraction system integration
requires thinner layer thickness with
impacts on pulp mill process and
same properties to become more
cellulose product quality.
attractive.
5
• Combined system shows promising
economic performance compared to
• Many products and technologies
may be challenging.
Case 1 because of improved yield and
• Sawdust has other competing uses.
integration into pulp mill.
• Compatibility of the hot water
• Lignin separation system is very
extraction based high molecular
• Further analysis of the compatibility
of the products in the end
applications (barriers, animal feed,
lignin in composite).
• Evaluate which product combination
small compared to e.g. announced
weight hemicelluloses for barrier
generates most value from the
Lignoboost projects and requires
application.
feedstock.
significant investment.
29
obtaining information that could be difficult to
techniques
measure experimentally. The new models were
technologies, or the costs of modifying the
implemented on a digester modelling platform,
lignin for biocomposite production. The results
which can be used for simulation of industrial-
of the sustainability analysis on the other
scale continuous hot water extraction units.
hand highlighted the opportunities offered
Simulation of a hot water extraction and
by the selected concepts to different players
alkaline pulping sequence for the production
in the value chain. This new information
of dissolving pulp could be one possible case
on business potential can be exploited by
study. Furthermore, the models for hot water
companies using the concept and companies
extraction phenomena (incl. xylan degradation
developing enabling technologies for the value
kinetics, chain scission and diffusion in a chip,
chain. Moreover, the refined overall techno-
and digester flow) can supplement concept
economic analysis approach can be utilized for
modelling
evaluating other new technologies than those
of
processes
using
hot
water
extraction.
compared
to
more
mature
developed in FuBioJR2.
The light techno-economic analysis revealed
the potential of the technologies developed
6. Networking
in FuBio JR2. For example, the potential of
integrating the PHWE system into different
A
host processes, the preliminary economic
contributions in this context is presented in
performance of new hydroxy acids separation
Table 5.
summary
of
the
partners
and
their
Table 5. Partner organizations and their research roles.
Work package partners
Role of the participating organization
Aalto University
Physico-chemical modelling of hot water extraction and
implementation of the model into a process simulator, kinetic
modelling of hot water extraction at chip and reactor level
Andritz
Work Package Coordinator
GloCell
Quantitative analysis in the techno-economic modelling, market
entry evaluation method development
Kemira
Industrial tutor
Lappeenranta University of Technology
Multivariate analysis
Metsä Fibre
Industrial tutor
Pöyry Management Consulting
Techno-economic assessment through investment and
production costs and qualitative opportunity assessments
Stora Enso
Industrial tutor
University of Oulu
Social impact assessment
UPM-Kymmene
Industrial tutor
Valmet
Industrial tutor
VTT
WP leader. Early-stage techno-economic modelling and method
development, new biorefinery process integration method
development, process concept design and process modelling,
life cycle assessment
30
7. Publications and reports
Abdulwahab, M. Modelling of ionic liquids' ther-
Liu, Z., Ahmad, W., Kuitunen, S. and Alopaeus,
mal separation and recycling in biomass frac-
V. Modeling of mass transfer and degradation
tionation, M.Sc. Thesis, Aalto University, 2013.
of hemicelluloses in flow-through hot water extraction, Submitted to Industrial & Engineering
Borrega, M., Nieminen K. and Sixta, H. Deg-
Chemistry Research.
radation kinetics of the main carbohydrates
in birch wood during hot water extraction in a
Liu, Z., Suntio, V., Kuitunen, S., Roininen, J.
batch reactor at elevated temperatures, Biore-
and Alopaeus, V. Modeling of mass transfer
source Technology, 102, 2011, 10724-10732.
and reactions in anisotropic biomass particles
with reduced computational load, Industrial
Hytönen, E. and Leppävuori, J. Future Biore-
& Engineering Chemistry Research, 53, 2014,
finery (FuBio) research into process concepts –
4096 - 4103.
early stage process evaluation and screening,
Nordic Wood Biorefinery Conference NWBC
Visuri, J., Song, T., Kuitunen, S., and Alopaeus,
2014, Stockholm, Sweden, March 25-17, 2014.
V. Model for Degradation of Galactoglucomannan in Hot Water Extraction Conditions, Indus-
Kleen, M. Statistical modelling of pressurized
trial & Engineering Chemistry Research, 51,
hot water flow-through extraction process, VTT
2012, 10338-10344.
Research Report, VTT-R-2688-14, May 2014.
Kleen, M. Statistical modelling of pressurized
hot water batch extraction process, VTT Research Report, VTT-R-2637-14, May 2014.
Kleen, M., Pranovich, A. and Willför, S. Statistical modeling of pressurized hot water extraction process to produce hemicellulose with desired properties, 4th International Conference
on Biorefinery—towards Bioenergy (ICBB2013),
Xiamen, China, December 3-5, 2013.
Kuitunen, S. Phase and reaction equilibria in the modelling of hot water extraction,
pulping
and
bleaching
(http://urn.fi/
URN:ISBN:978-952-60-5618-0), Doctoral dissertation, Aalto University, 2014.
Kuitunen, S., Vuorinen, T. and Alopaeus, V.
The role of Donnan effect in kraft liquor impregnation and hot water extraction of wood, Holzforschung, 67, 2013, 511-521.
31
NEW SOLUTIONS
FOR BIOMASS
FRACTIONATION
BY PRESSURIZED HOT WATER
EXTRACTION, SUPERCRITICAL
WATER TREATMENT AND
DELIGNIFICATION
CONTACT PERSON – Work Package 1 leader Risto Korpinen, [email protected]
Aalto University: Fanny Bardot, Marc Borrega, Herbert Sixta, Lasse Tolonen, Yuying Zhang.
Andritz: Christian Järnefelt, Tiina Rauhala
Finnish Forest Research Institute: Olli Byman, Sanna Hautala, Hannu Ilvesniemi, Petri Kilpeläinen,
Veikko Kitunen, Kaisu Leppänen, Zhiqiang Li, Johanna Tanner, Teemu Tikkanen
Kemira: Marcus Lillandt, Anna-Maija Saariaho
Lappeenranta University of Technology: Mohammed Al-Manasrah, Mari Kallioinen, Elsi Koivula,
Mika Mänttäri, Minna Nevalainen, Tuomas Nevalainen, Liis Retsja
Metsä Fibre: Ismo Reilama
Stora Enso: Kalle Ekman
University of Helsinki: Maija Tenkanen
University of Jyväskylä: Raimo Álen, Jarkko Kuivanen, Joni Lehto, Mika Leppäaho
UPM-Kymmene: Ulf Hotanen, Mika Hyrylä
VTT Technical Research Centre of Finland: Anne Kallioinen, Marjatta Kleen, Hanna Kyllönen, Tiina Liitiä,
Marjo Määttänen, Tarja Tamminen
Åbo Akademi University: Ricardo Garcia de Castro Insua, Henrik Grénman, Jarl Hemming, Jens Krogell,
Zhiqiang Li, Andrey Pranovich, Jan-Erik Raitanen, Jussi Rissanen, Tapio Salmi, Annika Smeds,
Maunu Toivari, Stefan Willför, Chunlin Xu
32
ABSTRACT
Pressurized hot water extraction (PHWE) and subsequent delignification processes
were examined for their ability to separate hemicelluloses, lignin and cellulose from
wood biomass. In addition, the separation and purification of PHWE extracts and hightemperature hydrothermal treatment of microcrystalline cellulose were also studied.
PHW extraction parameters were successfully tailored to enable the extraction of relatively
large amounts of hemicellulose of relatively high molar mass from wood. If molar mass is
not considered a critical factor, nearly all hemicelluloses – constituting approximately up
to one third of wood biomass – were extractable. Additionally, the pH of the PHWE process
was monitored and adjusted as desired by the addition of dilute alkali.
The hemicellulose-rich extracts obtained by PHWE contain mixtures of hemicelluloses of
varying chain length. A variety of impurities, such as wood extractives and lignin-derived
compounds, are also present. In addition, the dry solids content of the extracts is usually
relatively low. It was possible to concentrate, purify and fractionate the extracts according
to molecular size by combining appropriate pre- and/or post-treatments with membrane
filtration, while maintaining sufficient filtration capacity.
Crystalline cellulose residues were successfully hydrolyzed and dissolved by rapid nearand supercritical water treatments to produce narrowly distributed, low-molar-mass
celluloses and cello-oligosaccharides.
The fibrous fraction after PHWE was further isolated as a cellulose-rich fraction by sulfurfree delignification processes. Hardwoods defibrated more readily than softwoods due to
differences in lignin structure. The cellulose-rich fraction can be further processed into
various products, such as regenerated cellulose.
Keywords:
analytical methods, cellulose, delignification, hemicelluloses, lignin, pressurized hot water extraction,
pulp, purification, separation, super critical water, wood biomass
33
1. Background
2. Objectives
The structural building blocks of wood –
I) Investigation of the use of pressurized hot
hemicelluloses, lignin and cellulose – account
water
for the vast majority of all woody biomass.
treatment for the fractionation of wood. II)
Pressurized hot water extraction (PHWE) offers
Concentration and purification of the obtained
an environmentally sound water-based means
hemicellulose- and lignin-containing fractions
of separating out these valuable components.
to enable their utilization in various applications.
The extracted hemicellulose and lignin fractions
III) Further delignification of the extracted
offer a source of valuable biochemicals and
residues to produce novel pulps. IV) Transfer
other bioproducts, thus contributing to reduced
of knowledge obtained from laboratory scale
reliance on petrochemicals, while the cellulose-
experiments to the pilot scale.
extraction
and
supercritical
water
rich fibre fraction can be used in composites or
further processed into new fibre products or
regenerated cellulose.
3. Research approach
In the PHWE process, wood is treated with
Spruce and birch wood were pressurized hot
water at elevated pressure and temperature,
water extracted using different reactor setups
up to 220 °C, to separate the hemicellulose-
(batch, flow-through and cascade). The reactor
rich fraction from the wood matrix. No organic
volumes varied from 33 ml to 300 l. An example
solvents or toxic chemicals are needed. The
of a batch mode setup, accelerated solvent
attained fibre fraction subsequent to PHWE is
extraction (ASE) system, used in the PHWE
further fractionated into lignin and cellulose
experiments can be seen in Figure 1. Different
by sulfur-free delignification processes and
extraction parameters were studied, such as
possible additives.
temperature, pressure, time and particle size.
Pressurized hot water treatment in near- and
The aim of the extractions was to produce as
supercritical
distinct
high-molar-mass hemicelluloses as possible
liquid and gas phases are absent, can be used
at high yield. The extracted residues were
to achieve rapid hydrolysis and dissolution
delignified using sulfur-free processes. The
of crystalline cellulose residue to produce
aim was to produce pulps suitable for the
low molar mass polymer without addition of
production of regenerated cellulose and other
cellulose solvent.
products. The hemicellulose-rich extracts were
conditions,
in
which
fractionated, concentrated and purified using
Isolation of hemicellulose, lignin and cellulose
membrane filtration and different purification
from each other by PHWE is, however, not
techniques.
complete and the obtained fractions thus
were hydrolyzed and dissolved by rapid near-
contain a variety of impurities. In addition,
and supercritical water treatments in order to
the fractionation processes are relatively
produce narrowly distributed, low molecular
water intensive. Therefore, purification and
weight celluloses and cello-oligosaccharides at
dewatering processes are needed to enable
high purity. Analytical methods needed in the
utilization
wood fractionation processes were mapped
of
applications.
34
these
fractions
in
various
Crystalline
cellulose
residues
and method comparisons were carried out.
4. Results
4.1 Key results of PHWE
Particle size and temperature had a significant
effect on the extraction of hemicelluloses, as
illustrated in Figures 2 and 3. Norway spruce
sapwood of different particle sizes (0.25–1.0
mm vs. 8–12 mm) was pressurized hot water
extracted using different extraction times
and temperatures. The smaller particle sizes
resulted in a considerably higher amount of total
dissolved solids in the extracts. Furthermore,
higher
extraction
temperature
resulted
in
higher hemicellulose yield, but the average
Figure 1. Accelerated solvent extractor ASE 350.
a)
molar mass of the hemicelluloses decreased. At
b)
Figure 2. Amount of dissolved wood substances in extract as a function of extraction temperature and time,
a) sawdust and b) blocks.
a)
b)
Figure 3. Average molar mass of ethanol precipitated hemicelluloses from extracts as a function of
extraction temperature and time, a) sawdust and b) blocks.
35
higher temperature and prolonged extraction
4.2 Up-scaling experiences of PHWE
time, more intense hydrolytic degradation
of
place.
Two pilot scale PHWE appliances were used to
Additionally, larger wood particles cause mass
carbohydrates
and
lignin
takes
demonstrate the extraction results obtained
transfer limitations, preventing molecules from
from laboratory experiments. Figure 5 shows
migrating out from the wood matrix.
the 300-litre reactor (flow-through mode)
and the 30-litre reactor (both batch and flow-
Monitoring and controlling pH is essential.
through modes). Due to the large size of
If the pH drops too low during extraction the
these reactors compared to laboratory scale
hemicellulose chains start to degrade and
reactors, they were also used to produce
lower molar mass is obtained. The pH values of
sufficient amounts of extracts and PHWE-
the extracts were typically measured at room
treated fibres for further processing.
temperature after removing the samples from
the reactor. This resulted in a delay in the data.
It was shown that the laboratory scale
To avoid this, high-temperature pH electrodes
extractions could be up-scaled by a factor of
were installed and tested. As Figure 4 shows,
300 and 6000. The results of birch wood flow-
the pH measured inside the reactor during
through pressurized hot water extraction at the
PHWE was approximately 0.5 units higher
laboratory scale and pilot scale using the same
than that measured at room temperature. A
extraction conditions and reactor dimensions
difference of 0.5 pH units corresponds to a 3.2
are shown in Table 1.
times lower H+ concentration. It can also be
seen that by adding dilute alkali and using high-
The
temperature pH electrodes it was possible to
hemicelluloses extracted from birch wood were
amounts
and
extraction
rates
of
adjust and maintain the pH at the desired level.
similar for both the laboratory and pilot scale,
as shown in Figure 6. In addition, the pH profile
of the extracts was identical.
Figure 4. In-line pH control during PHWE at 170 °C.
36
a)
b)
Figure 5. Pilot scale PHWE reactors, 300 l flow-through (a) and 30 l batch and flow-through (b).
Table 1. Laboratory- and pilot scale extraction conditions.
Laboratory scale (0.05 l)
Pilot scale (300 l)
Temperature
160 °C
160 °C
Diameter / length, ratio
34 mm / 59 mm, 0.6
590 mm / 1040 mm, 0.6
Flow rate
3.3 ml/min
20 l/min
Residence time
12 min
12 min
Extraction time
60 min
60 min
Based on the modelling work done in the
in batch mode. The obtained model values and
laboratory using a 100 ml reactor, pilot scale
the pilot scale results were comparable (Table 2)
extractions of spruce wood were carried out
although the pilot- and laboratory scale PHWE
using a 30-litre reactor (scale-up factor 300)
setups had slightly different configurations.
a)
c)
b)
d)
Figure 6. a) pH of the extracts, b) hemicellulose yield and average molar mass, c) cumulative yield of
hemicellulose, d) chemical composition of extracts after 60 min extraction. Error bars represent the
relative standard deviations of three parallel extractions.
37
Table 2. Comparison of values from a statistical model based on laboratory- and pilot scale results.
Model values
(100 ml)
155 °C, 25 min,
W:W 5
Pilot results
(30 l)
155 °C, 25 min,
W:W 5
Model values
(100 ml)
170 °C, 20 min,
W:W 10
Pilot results
(30 l)
170 °C, 20 min,
W:W 10
pH of extract
4.2
3.9
3.7
3.6
Extraction residue yield,
% of orig.
94.7
93.2
86.1
82.8
Total dissolved solids
(TDS), mg/g wood
67.0
56.5
138.0
161.4
17800
13936
9600
8346
23.8
27.2
67.2
90.5
Average Mw, Da
GGM content of extract,
mg/g wood
Spruce extractions using batch mode and
in the extract was 63 mg/g after PHWE and 118
30-litre reactor were performed either at 160
mg/g after PHWE, washing and compression,
°C for 40 min or at 170 °C for 60 min, both
representing an 87% increase in TDS. Furthermore,
with a water-to-wood (W:W) ratio of 5 or 10.
the molar masses of the different washing and
After PHWE and removal of the extract, the
compression fractions were maintained.
extracted residue was washed at 50 °C for 30
min using the same W:W as in the extraction.
The pilot scale PHWE experiments showed that it
The amount of dissolved material was doubled
was possible to obtain relatively high-molar-mass
by using a W:W ratio of 10 instead of 5 in the
hemicelluloses at relatively high yield by using:
milder extraction conditions, as seen in Figure
7. In the harsher conditions, about 70% more
• Moderate extraction temperature range
TDS was obtained when using a W:W ratio of
(155–165 °C)
10. Slightly lower molar mass hemicellulose was
• Relatively short extraction time (25–35 min)
obtained when a higher W:W ratio was used.
• High packing degree of wood in the reactor
• Moderate water-to-wood ratio (5–10:1)
The amount of dissolved material in the extract
• Washing and compression of the wood after
could be further increased by compressing the
wood material after the extraction and washing
extraction
• Secondary wall exposed wood by means of
stages, as seen in Figure 8. The dissolved material
mechanical treatment
a)
b)
Figure 7. Total dissolved solids (a) and average molar mass (b) of PHW extracts and wash water from
spruce wood.
38
a)
b)
Figure 8. Total dissolved solids (a) and average molar mass (b) of PHW extract, wash water and compression
water from spruce wood.
4.3 Near- and supercritical water treatment
shares of the reaction products depended on
the treatment time and temperature for the
Near- and supercritical water treatment rapidly
two different microcrystalline celluloses, as
hydrolyzed and dissolved the recalcitrant
seen in Figure 10.
crystalline cellulose and produced a mixture of
cellulose polymers of varying molar mass. The
Dissolution as a precipitating polymer was
used reactor setup can be seen in Figure 9.
promoted by increasing the temperature, in
particular to above 320 °C, providing that the
After the treatment, the dissolved products
treatment time was kept sufficiently short
slowly precipitated as low molar mass and highly
to prevent extensive depolymerization of
crystalline cellulose with a narrow molar mass
the dissolved products. It was observed that
distribution. The rest of the dissolved material
wood-derived
remained in solution as oligo- and monosugars
(MCCs)
and
microcrystalline
exhibited
a
higher
celluloses
velocity
of
degradation
dissolution than those derived from cotton,
products formed via concomitantly occurring
possibly due to the dimensional differences
dehydration and retro-aldol reactions. The
of the cellulose crystallites.
a
mixture
of
various
a)
b)
Figure 9. “MIKKI” reactor system for near- and supercritical water treatment of microcrystalline cellulose
using short reaction times below one second (a). The short treatment time is achieved by rapid heating
with preheated supercritical water and quenching with cold water (b).
39
100 %
100 %
80 %
80 %
40 %
40 %
20 %
0%
250
260
270
280
290
300
310
320
330
340
350
360
370
380
20 %
0%
60 %
Other
Water-soluble sugars
Precipitate
MCC from
Residue
prehydrolysis Kraft pulp
Temperature (°C)
a)
b)
MCC from
Cotton linter
250
260
270
280
290
300
310
320
330
340
350
360
370
380
60 %
Temperature (°C)
Figure 10. Mass balances of two microcrystalline celluloses prepared by acid hydrolysis from prehydrolysis
kraft pulp (a) and cotton linter (b). Microcrystalline celluloses were treated in sub- and supercritical water
with varying temperature. Treatment time 0.20 s and pressure 250 bar.
Supercritical water treatment has potential
and part of the lignin prior to pulping. The
for
intensity of PHWE was described by a modified
cello-oligosaccharide
production
with
the advantage that cellulose dissolution and
P-factor (here Log Pxs). Soda-AQ pulping
hydrolysis can be carried out in a single stage. Other
experiments were then conducted at 150 °C,
techniques require the use of a cellulose solvent to
with 22% NaOH and 1% AQ, based on initial
dissolve cellulose crystallites and heterogeneous
dry wood. The yield of main wood components
hydrolysis, e.g. by acid hydrolysis processes,
from birch wood after hot water extraction and
mainly produces only monosaccharides. Cello-
soda-AQ pulping are shown in Figure 12.
oligosaccharide production was demonstrated
by treating commercially available MCC powder
The cellulose content of the pulp remained
in supercritical water at 380 °C for reaction
unaffected up to a hot water extraction
times of 0.2, 0.4 and 0.6 s (Table 3 and Figure
intensity (Log Pxs) of about 4.5 (Figure 12 b),
11). Up to 42% yield of cello-oligosaccharides
but higher intensities led to extensive cleavage
was reached with the 0.4 s treatment.
of glycosidic bonds, thus facilitating the
occurrence of peeling reactions and resulting
4.4 Delignification of PHWE-treated fibres
in a cellulosic pulp with low yield. Nonetheless,
unbleached pulps with an acceptable yield (over
Pressurized hot water extractions of birch wood
30% based on initial dry wood), and containing
chips at temperatures between 180 °C and 220
over 90% cellulose, less than 5% xylan, and
°C were conducted to extract hemicelluloses
about 2–3% lignin, were produced.
Table 3. Yield of undissolved residue, precipitate, cello-oligosaccharides and monosaccharides after a
supercritical water treatment at 380 °C and 250 bar for 0.2–0.6 s.
40
Treatment time
(s)
Residue
(%)
Precipitate
(%)
DP2–9 Cellooligosaccharides
(%)
Monosaccharides
(%)
0.2
8
35
29
3.0
0.4
0
11
42
6.1
0.6
0
<1
30
9.1
a)
b)
Figure 11. (a): Oligomer concentrations in water solution after supercritical water treatment, analyzed by
HPAEC-PAD in aqueous solution (PA100 column). (b): Molar mass distributions of the solid precipitate fraction.
Analyzed by GPC-RI system (4 x PL-mixed A columns) after dissolution in anhydrous 90 g/L LiCl/DMAc.
a)
b)
Figure 12. Cumulative yields of main birch components in wood residue after hot water extraction (a) and in
the pulp after soda-AQ pulping (b), plotted as a function of hot water extraction intensity (Log Pxs).
Selected wood residues after the pressurized
similar to the viscosity of pulp produced from
hot water extractions were subjected to
untreated wood. At higher extraction intensities
SAQ pulping (0.1% AQ) with the addition of
the viscosity rapidly decreased, reaching a
carbohydrate
sodium
minimum slightly above 100 ml/g. The addition
borohydride (BH) and anthraquinone-2-sulfonic
of stabilizing agents against peeling had little
acid sodium salt (AQS). The addition of 1% AQS
effect on pulp viscosity.
stabilization
agents
had no clear effect on the yield of carbohydrates,
whereas the addition of 1% BH resulted in an
The soda-AQ cooks of untreated and PHWE-
average yield increase of about 3%, similar to
treated birch sawdust were conducted under
the yield obtained by increasing the AQ charge
varying conditions: i.e., alkali charge 18, 20, and
from 0.1 to 1%. The yield increase was mostly
22% on o.d. feedstock, AQ charge 0.1% on o.d.
due to stabilization of cellulose, although xylan
feedstock, cooking time 90, 120, and 150 min,
was also preserved to some extent. The intrinsic
temperature 170 °C, and liquor-to-feedstock
viscosity of unbleached pulps derived from low-
ratio 5 l/kg. Pulp yields of the soda-AQ-cooks
intensity autohydrolysis (log Pxs < 4.25) was
are presented in Table 4.
41
Table 4. Birch soda-AQ cooking yield.
Soda-AQ cooks of birch wood
18% NaOH
Time,
20% NaOH
22% NaOH
Ref
PHWE*
PHWE**
Ref
PHWE*
PHWE**
Ref
PHWE*
PHWE**
min
90
51.6
53.5
38.5
50.4
54.0
38.8
49.1
52.8
38.0
120
50.9
53.1
38.1
49.7
53.5
38.5
47.6
51.4
37.0
150
51.1
52.9
38.0
49.1
51.6
37.1
47.8
50.7
36.5
*Cooking yield (% of material charged into the reactors). **Total cooking yield (% of oven-dry feedstock
before pre-treatment).
Clearly higher yields were achieved with the
170 °C, and liquor-to-wood (L:W) ratio 5 l/
reference material (untreated birch sawdust)
kg. The cooking liquor was first bubbled
compared to the pressurized hot water extracted
with oxygen (for 5 minutes) and an oxygen
materials. On the other hand, the colour of the
atmosphere was then created in the reactors
pulp produced from PHW extracted feedstocks
by an oxygen flow. The oxygen-alkali cooking
was clearly lighter (visible difference). Clearly
yields for both feedstocks are presented in
lower kappa numbers were achieved with pulps
Table 6.
produced from the PHW extracted materials, as
seen in Table 5. As the table shows, the kappa
Again, clearly higher cooking yields were
numbers were very low, especially when pulping
achieved with the reference material (untreated
was conducted with pressurized hot water
sawdust) when compared to the pressurized
extracted feedstocks (T, “treated”).
hot water extracted materials. In general,
PHWE-treatment conducted before oxygen-
Cooking experiments were also conducted
alkali
using oxygen-enhanced alkali cooking with
especially with birch sawdust. However, only
cooking
facilitated
the
defibration,
untreated and PHW extracted birch and spruce
very slight improvement could be observed
sawdust. The same cooking equipment was
in the case of spruce. Overall, spruce sawdust
used for the oxygen-alkali cooks as for soda-
was very poorly defibrated during oxygen-
AQ cooks. The cooking conditions were: alkali
alkali cooking experiments. Pulp reject after
charge 19% on o.d. feedstock, cooking time
screening (material not passing a 0.2-µm sieve,
30, 60, 90, 120, and 150 minutes, temperature
% of cooking yield) is presented in Table 7.
Table 5. Kappa numbers of the birch soda-AQ pulp samples.
Time, min
18 % NaOH
20 % NaOH
22 % NaOH
90 (NT*)
14.9
11.8
10.2
90 (T*)
6.4
5.5
5.5
120 (NT)
13.3
11.1
9.8
120 (T)
5.8
5.4
5.5
150 (NT)
12.2
11.0
9.3
150 (T)
5.4
4.6
5.6
*NT= not treated (i.e., no PHWE), T= treated
42
Table 6. Spruce and birch oxygen-alkali cooking yields.
Oxygen-alkali cooks
Birch
Spruce
19% NaOH
19% NaOH
Time, min
Ref
PHWE*
PHWE**
Ref
PHWE*
PHWE**
30
59.5
59.7
42.9
67.9
74.4
56.2
60
56.8
54.7
39.3
63.5
70.3
53.1
90
55.4
52.4
37.9
60.3
66.2
50.0
120
54.1
52.3
37.6
58.3
63.8
47.7
150
51.2
50.0
36.0
57.4
61.3
46.3
*Cooking yield (% of material charged into the reactor). **Total cooking yield (% of oven-dry feedstock
before pre-treatment).
Table 7. Pulp reject (% of cooking yield) after oxygen-alkali cooking.
Time (min)
Birch (Ref)
Birch (PHWE)
Spruce (Ref)
Spruce (PHWE)
30
70.2
29.9
86.0
82.6
60
68.9
11.5
85.4
79.9
90
64.6
3.8
81.5
76.6
120
57.9
1.7
81.0
75.8
150
47.2
ND
80.7
73.4
4.5 Separation and purification of
hemicellulose-rich extracts
ultrafiltration (10 kDa) regenerated cellulose
membrane is used and filtration is performed
using a high shear rate filter. High volumes of
Hemicellulose-rich wood extracts after PHWE
water and small compounds can be removed
contain relatively large amounts of water
from the extract with a reasonable filtration
and impurities which need to be removed
before further utilization. Membrane filtration
is a convenient method for simultaneously
concentrating and fractionating the extract.
Pilot scale membrane filtration equipment
(Figure 13) was used to separate high-molarmass hemicelluloses from the PHWE extracts.
The
results
from
several
concentration
filtration experiments performed at the pilot
scale revealed that concentration of wood
extracts
to
produce
a
high-molar-mass
hemicellulose fraction can be done using
a relatively high filtration capacity (flux)
without any pre-treatment when a hydrophilic
Figure 13. Cross-rotational (CR)-350 ultrafiltration
equipment, membrane area 1 m2.
43
capacity (> 100 kg/(m2 h)) (Figure 14). The flux
2.5 bar (60 °C, circumferential velocity of rotors
gradually decreased as the feed concentration
8.6 m/s), indicating that the decrease in filtration
increased, which could be expected. However,
capacity occurring at the end of concentration
at a certain point the flux suddenly collapsed
filtration can be compensated by increased
(Figure 14). Changes in the feed composition
filtration pressure. Despite the significant flux
due to increasing concentration, i.e. increased
decline seen at the end of the concentrate
total solids content and average molar mass of
filtrations, the membranes were not significantly
compounds present in the feed, may have led
fouled and filtration capacity was easy to restore
to an increase in osmotic pressure difference
with simple alkaline cleaning.
across the membrane and increased viscosity.
In addition, the rheological properties of
Several pre-treatments for improving the
the feed may have changed as a result of
filtration capacity and increasing the purity
concentration. These combined factors may
of the resulting hemicellulose fractions were
have led to the considerable and rapid flux
investigated. For instance, a combination
reduction. It was found that the filtration
of pre-treatment, ultrafiltration and post-
capacity (flux) can be maintained at a good level
treatment was studied at laboratory scale
(about 95 kg/(m h)) if the pressure is increased
using a 40 cm2 RC70PP membrane with a 10
in line with the reduction in feed volume (i.e.
kDa cut-off. Spruce extract was first oxidized
increase in concentration) at least until the TDS
and then ultrafiltered and diafiltered at 60 °C
of the concentrated fraction is about 8% (Figure
and 2 bar. As Figure 15 shows, the combined
14). This was demonstrated in the experiments
purification and separation steps removed
in which spruce extract (TDS content 0.86%)
significant amounts of impurities from the
was fractionated in constant flux mode, where
extract, although some hemicellulose losses
the filtration pressure increased from 1.3 bar to
occurred in the process.
2
Constant pressure (2 bar)
200
Constant flux
Pressure at constant flux mode
Constant flux mode
TDS 3.79% at 4.8 h
Constant pressure mode
TDS 3.85% at 2.7 h
TDS(feed) 0.86%
3.0
180
2.5
Flux (60°C), kg/(m2h)
160
140
2.0
120
100
1.5
80
1.0
60
40
0.5
20
0
Pressure (constant flux mode), bar
0.0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Time, h
Figure 14. Filtration capacity in the treatment of spruce extract with the RC70PP membrane and
the CR-350 filter using constant pressure and constant flux filtration modes. Both experiments were
conducted at 60 °C with a rotor circumferential velocity of 8.6 m/s.
44
a)
b)
Figure 15. Chemical composition of original spruce extract before separation and purification (a) and
chemical composition of the concentrate after oxidative pre-treatment, ultrafiltration and diafiltration (b).
4.6 Analytical methods for compositional
and structural analyses
composition, the structural features of the
biomass fractions must also be examined in
order to evaluate the applicability and value of
In order to evaluate the efficiency of the
the material. The choice of analytical techniques
developed processes, the composition of the
depends on the sample matrix. In addition,
obtained fractions must be analysed. This
appropriate
is important for determining the purity and
applied. The most important analytical methods
mass balance of the fractions. In addition to
for the research challenges described above are
pre-treatments
must
also
be
Table 8. Analysis methods for solid wood and fibrous samples.
Solid wood and fibrous samples
Obtained information
Pre-treatment: grinding and sieving
Carbohydrate content and composition
- Acid methanolysis/GC
Hemicelluloses and uronic acids
- Acid hydrolysis (two-stage)-HPAEC/PAD
Cellulose and hemicelluloses
Extractives content and composition
- Extraction by ASE, Soxtec, Soxhlet with aceto- Total amount of (acetone soluble) extractives
ne, gravimetric detection
- Group analysis with short GC column
Quantitation of compound groups
- Analysis by GC-FID/GC-MSD
Identification of individual components
Lignin amount (after extraction)
- Acid hydrolysis, gravimetric analysis of residue
Total lignin as Klason lignin + acid soluble lignin
+ UV detection of the hydrolysate
Molar mass
- Dissolution (multi-step) in DMAc/LiCl - HPSEC
Molar mass distribution of cellulose (+hemicelluloses), calculated average values
ASE: Accelerated Solvent Extraction, FID: Flame Ionisation Detector, GC: Gas Chromatography, HPAEC:
High Performance Anion Exchange Chromatography, HPSEC: High Performance Size Exclusion
Chromatography, MSD: Mass Spectroscopic Detector, PAD: Pulse Amperometric Detector, UV: Ultraviolet.
45
listed in Tables 8, 9 and 10 for different sample
techniques, it was possible to follow the
matrices, including a brief description of the
formation
method and the information obtained. The
cellulose under supercritical water treatment
methods suggested for solid wood and fibrous
conditions (Tolonen et al. 2014). The other
samples are based on either standard methods
methods mentioned in Table 9 are based on
or literature.
literature.
Molar mass is one of the most crucial criteria
Lignin was partly extracted in the PHWE
for determining hemicellulose quality. Lignin is
treatments along with hemicelluloses as
always present in the hemicellulose fractions
an impurity. However, lignin is a valuable
either as such or linked to carbohydrates. This
component in itself with a range of potential
causes problems in molar mass analysis using
applications. The structure and properties
universal calibration with light scattering-
of lignin depend on its origin (raw material
based detection due to autofluorescence.
and process). The methods listed in Table 10
Because of the challenges related to this critical
provide useful information for evaluating the
measurement, a comparison between several
quality and properties of isolated lignins.
of
cello-oligosaccharides
from
methodologies was performed using hotwater extracted spruce galactoglucomannans
(GGM) and birch glucuronoxylans as substrates
(Xu et al. 2013). Four different size exclusion
5. Exploitation plan and impact of
results
chromatography (SEC) configurations used
by different partners were compared. Ethanol
The main objective was to generate a concept
precipitations were carried out on the birch
based on pressurized hot water extraction
and spruce extracts to explore the effect of
(PHWE)
lignin content on molar mass.
hemicelluloses at high yield from wood of
for
producing
high-molar-mass
varying particle size. Another goal was to
The difference in Mw values of the birch samples
utilize the remaining fibre fraction after PHWE
was found to be relatively larger than that of
for the production of new fibre products and
the spruce samples, presumably because
regenerated cellulose. Because no entirely
the birch extracts contained more lignin than
pure fractions can be separated from wood,
spruce. The difference in Mw values before
comprehensive studies of separation and
and after ethanol precipitation was similarly
purification technologies required for these
ascribed to differences in lignin content of the
processes were also carried out. Furthermore,
birch and spruce samples. In addition, the Mw
fundamental understanding of the factors
values determined by RI increased during the
affecting PHWE and subsequent delignification
precipitation–dissolution cycle, probably due
processes is needed for developing industrial-
to aggregation. It was therefore not possible to
scale processes. These general objectives
identify an optimal method for all sample types.
were met and the processes and knowledge
generated can be implemented, at least in
Another
analytical
to
part, in industry. As a result, increased use
and
of biomass instead of oil for materials and
quantitation of individual oligosaccharides,
products will have a positive impact on society
either in their native form or in altered form
and contribute towards a sustainable future.
hemicelluloses
is
challenge
the
related
identification
during processing. By combining several
chromatographic and mass spectroscopic
46
Table 9. Analysis methods for PHWE extracts and isolated hemicelluloses.
PHWE extracts and isolated hemicelluloses
Solids content, gravimetric
Total amount of dissolved material
Carbohydrate content and composition
- Freeze-drying-acid methanolysis/GC
Hemicelluloses and uronic acids
- Weak acid hydrolysis-HPAEC/PAD
Hemicelluloses
Lignin amount
- Acidic solutions: direct UV detection or freeze-drying
- acetyl bromide or Klason lignin
Content of dissolved lignin
Acetic acid / formic acid, degree of acetylation
- HPLC, CE or benzylation-GC/MS
Content of volatile acids
- Alkaline hydrolysis + analysis of acetic acid
Degree of acetylation
Furfural-type degradation products
- HPLC or CE
Content of furfural and hydroxymethylfurfural (HMF)
Other degradation products
- Silylation-GC/MS
(Hydroxy)acids
Molar mass distribution of dissolved hemi and lignin
- HPSEC-various detectors*
Molar mass distribution and calculated average values
Oligosaccharides
- HPAEC-PAD/MSQ**
Quantitative analysis of oligosaccharides if standards
available, otherwise tentative identification by MSQ
(as deacetylated analogues)
- MALDI-TOF-MS, AP-MALDI-MS/MS, ESI-MS/MS**
Identification including native acetylation
AP: Atmospheric Pressure, CE: Capillary Electrophoresis, ESI: Electron Spray Ionisation, HPLC: High
Performance Liquid Chromatography, MALDI: Matrix Assisted Laser Desorption Ionisation, MS: Mass
Spectrometry, MSQ: Quadrupole Mass Spectrometry, TOF: Time of Flight, other abbreviations as in Table
8. * For method comparison, see text above and ref. Xu et al. 2013. ** For application example and details,
see text above and ref. Tolonen et al. 2014.
Table 10. Analysis methods for isolated lignin.
Isolated lignin
Composition
- Ash content (metals) by incineration
Organic content
- Carbohydrate content: hydrolysis and HPAEC/PAD
Lignin-Carbohydrate Complexes (LCC)
Structure
- Derivatisation-31P NMR
Frequency of hydroxyl functionalities
- 1D and 2D NMR techniques
Substructures and inter-unit linkages
- Pyrolysis-GC/MS
Fingerprint, mainly for sample comparison
Molar mass
- HPSEC-UV in NaOH
Molar mass distribution
Elemental analysis (CHONS)
Elemental composition
Thermal properties
- Glass transition temperature by DSC, degradation
Transitions and degradation as a function of tempe-
by TGA
rature
CHONS: Carbon, Hydrogen, Oxygen, Nitrogen and Sulfur, DSC: Differential Scanning Calorimetry, NMR:
Nuclear Magnetic Resonance, TGA: Thermogravimetric Analysis, other abbreviations as in Tables 8 and 9.
47
6. Networking
The research was carried out jointly by Aalto University, the Finnish Forest Research Institute,
Lappeenranta University of Technology, University of Helsinki, University of Jyväskylä, VTT Technical
Research Centre of Finland, Åbo Akademi University and Finnish Bioeconomy Cluster companies.
Table 11 presents the research partners and their roles.
Aalto University
Pressurized hot water extraction, near- and
supercritical water treatment, delignification
Andritz
Industrial tutor
Finnish Forest Research Institute
Pressurized hot water extraction, purification,
delignification
Kemira
Lappeenranta University of Technology
Membrane filtration, separation, purification
Metsä Fibre
Industrial tutor
Stora Enso
Industrial tutor
University of Helsinki
Enzymatic hydrolysis, analytical methods
University of Jyväskylä
Delignification, characterization of black liquor
UPM-Kymmene
Industrial tutor
VTT
Pressurized hot water extraction, analytical
methods, enzymatic hydrolysis, modelling,
delignification, green liquor extraction
Åbo Akademi University
WP leader. Pressurized hot water extraction,
analytical methods, purification, reaction
kinetics, hydrolysis by heterogeneous
catalysis, chemical characterization,
delignification
48
Bardot, F. Cellulose stabilization during alkaline
Kilpeläinen, P., Kitunen, V., Pranovich, A., Il-
pulping for the production of high‐purity dis-
vesniemi, H. and Willför, S. Pressurized hot
solving‐grade pulp, Master’s thesis, Aalto Uni-
water flow-through extraction of birch saw-
versity, 2012.
dust with acetate pH buffer, BioRes., 8, 2013, 4,
5202–5218.
Borrega, M., Tolonen, L.K., Bardot, F., Testova,
L. and Sixta, H. Potential of hot water extrac-
Kilpeläinen, P., Hautala, S. Byman, O., Tan-
tion of birch wood to produce high‐purity dis-
ner, J., Korpinen, R., Lillandt, M., Pranovich,
solving pulp after alkaline pulping, Bioresource
A., Kitunen, V., Willför, S. and Ilvesniemi, H.
Technology, 135, 2012, 665–671, DOI: 10.1016/j.
Pressurized hot water flow-through extraction
biortech.2012.11.107.
system scale up from laboratory to pilot scale,
Green Chem., 2014, DOI: 10.1039/C4GC00274A.
Borrega, M., Niemelä, K. and Sixta, H. Effect
of hydrothermal treatment intensity on the for-
Koivula, E., Kallioinen, M., Sainio, T., Antón,
mation of degradation products from birch-
F.E., Luque, S. and Mänttäri, M. Enhanced
wood, Holzforschung, 67, 2013, 8, 871–879, DOI:
membrane filtration of wood hydrolysates for
10.1515/hf-2013-0019.
hemicelluloses recovery by pretreatment with
polymeric adsorbents, Biores. Tech., 143, 2013,
Borrega, M. and Sixta, H. Purification of cel-
275-281.
lulosic pulp by hot water extraction, Cellulose,
20, 2013, 2803–2812, DOI 10.1007/s10570-0130086-1.
Korpinen, R., Kallioinen, M., Hemming, J.,
Pranovich, A., Mänttäri, M. and Willför, S.
Comparative evaluation of various lignin deter-
Garcia de Castro Insua, R. Acid hydrolysis of
mination methods on hemicellulose-rich frac-
birch and spruce hemicelluloses by heteroge-
tions of spruce and birch obtained by pres-
neous catalysis, Master’s thesis, Åbo Akademi
surized
University, 2013.
subsequent ultrafiltration (UF), Holzforschung,
hot-water
extraction
(PHWE)
and
2014, DOI: 10.1515/hf-2013-0233.
Grénman, H., Eränen, K., Krogell, J., Willför, S.,
Salmi, T. and Murzin, D. Kinetics of Aqueous
Krogell,
Extraction of Hemicelluloses from Spruce in
Pranovich, A. and Willför, S. High-temperature
J.,
Eränen,
K.,
Granholm,
K.,
an Intensified Reactor System, Ind. Eng. Chem.
pH measuring during hot-water extraction of
Res., 50, 2011, 7, 3818–3828.
hemicelluloses from wood, Industrial Crops and
Products, 61, 2014, 9–15.
Kilpeläinen, P., Leppänen, K., Spetz, P., Kitunen, V., Ilvesniemi, H., Pranovich, A. and
Krogell,
Willför, S. Pressurised hot water extraction
Pranovich, A., Salmi, T., Murzin, D. and Willför,
J.,
Korotkova,
E.,
Eränen,
K.,
of acetylated xylan from birch sawdust, Nord.
S. Intensification of hemicellulose hot-water
Pulp Pap. Res. J., 27, 2012, 4, 680–688.
extraction from spruce wood in a batch extractor - Effects of wood particle size, Bioresource
Technology, 143, 2013, 212–220.
49
Kuivanen, J. Kuusen ja koivun jatkuvavirtauk-
Retsja, L. Puuperäisten biomassahydrolysaat-
sellinen paineistettu kuumavesiuutto, Master’s
tien likaamien membraanien pesu, Master’s the-
thesis, University of Jyväskylä, 2012.
sis, Lappeenranta University of Technology, 2013.
Lehto, J. and Alén, R. Purification of hardwood-
Rissanen, J., Grénman, H., Willför, S., Mur-
derived autohydrolysates, BioResources, 7,
zin, D. and Salmi, T. Spruce Hemicellulose for
2012, 1813–1823.
Chemicals Using Aqueous Extraction: Kinetics, Mass Transfer, and Modeling, Industrial &
Lehto, J., Alén, R. and Malkavaara, P. Multivar-
Engineering Chemistry Research, 53, 2014, 15,
iate correlation between analysis data on dis-
6341–6350.
solved organic material from Scots pine (Pinus
sylvestris) chips and their autohydrolysis pre-
Song, T. Extraction of polymeric galacto-glu-
treatment conditions, BioResources, 9, 2014,
comannans from spruce wood by pressurised
93–104.
hot water, Doctoral thesis, Åbo Akademi University, 2013.
Lehto, J., Alén, R., and Malkavaara, P. Multivariate correlation between analytical data for
Testova, L., Borrega, M., Tolonen, L.K., Pent-
various organics dissolved during autohydrol-
tilä, P.A., Serimaa, R., Larsson, P.T. and Sixta,
ysis of silver birch (Betula pendula) chips and
H. Dissolving-grade birch pulps produced un-
treatment conditions, BioResources, 9, 2014,
der various prehydrolysis intensities: quality,
4958–4970.
structure and applications, Cellulose, 2014, DOI
10.1007/s10570-014-0182-x.
Leppäaho, M. Kuumavesiuutetun kuusisahanpurun sooda-antrakinonikeitto, Master’s thesis,
Tikkanen, T. Paineistetulla kuumavesiuutolla
University of Jyväskylä, 2013.
tuotetun hemiselluloosarikkaan jakeen entsymaattinen puhdistaminen, Master’s thesis, Uni-
Li, Z. Optimisation of alkaline flow-through ex-
versity of Oulu, 2013.
traction of spruce wood for lignin recovery,
Master’s thesis, Åbo Akademi University, 2013.
Tolonen, L.K., Penttilä, P.A., Serimaa, R.,
Nevalainen, M. Ultrasuodatusmembraanin mo-
lution of cellulose crystallites in subcritical and
difiointi entsyymeillä suodatusominaisuuksien
supercritical water, Cellulose, 20, 2013, 6, 2731-
parantamiseksi, Master’s thesis, Lappeenranta
2744. doi:10.1007/s10570-013-0072-7.
Kruse, A. and Sixta, H. The swelling and disso-
University of Technology, 2013.
Tolonen, L.K., Juvonen, M., Mikkelson, A., NiePenttilä, P.A., Kilpeläinen, P., Tolonen, L., Su-
melä, K., Tenkanen, M. and Sixta, H. Super-
uronen, J.-P., Sixta, H., Willför, S. and Serimaa,
critical water treatment for cello-oligosaccha-
R. Effects of pressurized hot water extraction
ride production from microcrystalline cellulose,
on the nanoscale structure of birch sawdust,
Manuscript submitted to ChemSusChem 2014.
Cellulose, 20, 2013, 5, 2335–2347.
Xu, C., Korpinen, R., Hirsilä, P., Liitiä, T., Tuomainen, P., Tamminen, T., Willför, S. and Tenkanen, M. Effect of lignin on the molar mass
analysis of hot water extracted hemicelluloses,
FuBio Seminar, 27.8.2013, Helsinki, Finland.
50
IONIC LIQUIDS
FOR WOOD
FRACTIONATION
CONTACT PERSON – Work Package 2 leader Alistair W. T. King, [email protected]
Aalto University: Ville Alopaeus, Lauri Hauru, Michael Hummel, Yibo Ma, Alexandr Ostonen,
Annariikka Roselli, Erlin Sapei, Herbert Sixta, Petri Uusi-Kyyny
Andritz: Christian Järnefelt, Tiina Rauhala
Lappeenranta University of Technology: Mika Mänttäri, Olli Nakari, Arto Pihlajamäki
Metsä Fibre: Pirkko Liias
Stora Enso: Paula Rantamäki, Heidi Saxell
University of Helsinki: Jussi Helminen, Ashley Holding, Uula Hyväkkö, Tia Kakko, Ilkka Kilpeläinen,
Arno Parviainen
UPM-Kymmene: Ulf Hotanen, Mika Hyrylä
VTT Technical Research Centre of Finland: Anna Suurnäkki, Ronny Wahlström
Åbo Akademi University: Ikenna Anugwom, Valeri Eta, Jyri-Pekka Mikkola, Päivi Mäki-Arvela,
Pasi Virtanen
52
ABSTRACT
During FuBio 1, new concepts in wood processing with novel ionic liquids as potentially
environmentally benign reaction media were presented. These include a refinement in
our understanding about the effects that these unique solvators have on woody material
and examples of the new structures under development, which offer increased process
sustainability over the initial generations of ionic liquids.
Herein we present the updated results from these fractionation concepts, including
switchable ionic liquid (SIL, selective extraction of components) fractionation and ionic
liquid-aided fractionation (ILAF, homogeneous dissolution and selective precipitation of
components). One new concept is presented, called the IONCELL-P process, which is a
process for fractionation of kraft pulp into its higher-value pure components (cellulose
and hemicellulose). As ionic liquids must be recovered in all processes, we also present
the most up-to-date recyclable ionic liquid structures that have been developed during
the FuBio project (switchable: SIL; distillable: DIL; phase-separable: PSIL) and the methods
that are being used to assess ionic liquid purification (thermodynamics of distillation in
ionic liquids and membrane purification methods).
Overall, we have developed understanding that makes us highly competitive on the
international scale in the area of bioprocessing with ionic liquids.
Keywords:
fractionation, dissolution, biomass, distillable, switchable, sustainable, IONCELL
53
1. Background
1.1 Ionic Liquid Bioprocess Sustainability
ionic liquids (SILs), distillable ionic liquids (DILs)
and phase-separable ionic liquids (PSILs).
one
The results from fractionation of wood and
sustainable resource to replace fossil fuels.
subsequent recycling, using all classes of ILs
However, challenges exist in the incorporation
described above, are presented in this chapter.
Wood
is
regarded
as
the
number
of wood-based feedstocks and processes
into traditionally fossil-based value chains.
Therefore, new ‘tuneable’ methods offering
2. Objectives
more varied and improved selectivities for
the fractionation and processing of wood
The main application objectives of this work
biopolymers into materials, chemicals and
package were focussed on the development
energy are necessitated. The reported high
of processes that utilize ionic liquids, namely:
efficiency in the solvation of cellulose, as a
major wood component, by ionic liquids (ILs)
• Develop recyclable, cheap and low toxicity
has thus afforded new processing opportunities
ionic liquids that are capable of dissolving
whereby wood itself can be effectively solvated
cellulose, wood or extracting wood.
and processed accordingly. In addition, room
• Assess their potential for fractionation
temperature ionic liquids (RTILs), such as
of wood into its components of specified
1-ethyl-3-methylimidazolium acetate ([emim]
quality for novel processes or to fit into
[OAc], m.p. -45°C), offer so effective cellulose
solvation
capabilities
that
they
are
now
existing value chains.
• Assess the recyclability and purification
considered to be industrially viable media
of these ionic liquids before and after
for existing and novel cellulose processing
fractionation steps.
applications. An important example is in the
replacement of N-methylmorpholine-N-oxide
On the whole, the objectives called for the
hydrate (NMMO·H2O) in a ‘Lyocell’ process,
assessment of existing structures for their
circumventing
stability
efficiency in the fractionation of woody
issues. [emim][OAc] has been so successful in
material and for the development of new
cellulose solvation that BASF is now producing
ionic liquids. This was necessary due to the
it on a ton-scale. Publications are appearing,
poor stability and recyclability of existing
however, that highlight the instability of
structures. A general pre-requisite for new
[emim][OAc] in the presence of lignocellulosic
ionic liquids for the above application was
solutes, although this may be beneficial for
that they be effective at dissolving both lignin
homogeneous dissolution of wood as certain
and wood polysaccharides, such as cellulose
[emim][OAc]
or
hazardous
thermal
decomposition
products
are
hemicelluloses.
Determining
which
known to catalyse certain chemistries. In
biopolymers these ionic liquids dissolve or
regard to process sustainability, basic ILs such
extract from the substrate will dictate which
as [emim][OAc] are also known to have reduced
fractionation schemes can be applied.
thermal stabilities. This effectively prevents
the recovery of the IL on an industrial-scale by
distillation. As such, other methods of recycling
or more recyclable structures/systems were
sought during FuBio 1 & 2, e.g., switchable
54
Due to the infancy of ionic liquids research
• Develop structure property relationships
and the structural complexity of ionic liquids
in regard to the physical properties of the
in comparison to molecular solvents, this
ionic liquids (e.g. thermal stabilities) and the
work package demanded a more academic
observed effects and phenomena (mainly
approach. This was conducted alongside
biopolymer solubilities). This was achieved
assessment of ionic liquids for their efficacy
through a process of parameterization of
for the processing of lignocellulosics. Three
effective and non-effective ionic liquids.
main areas were focused on (Scheme 1).
Computational methods were also used
to predict physiochemical properties of
The research strategy outlined in Scheme 1 can
be summarized as follows:
structures.
• Through this understanding of effects,
parameters and the generation of new
• The starting point was the synthesis of
existing imidazolium-based ionic liquids
• Next was to further our understanding of
different effects and phenomena that occur
when lignocellulosics are contacted with
ionic liquids (e.g. dissolution capabilities,
structures, it was possible to develop
hypotheses about which structural features
would enable more advantageous effects
(e.g. lower viscosities or more recyclable
structures)
• New series of structures were synthesized
fractionation efficiency, fibrillation,
bringing an improved understanding of
chemical reaction).
physical properties and recycling issues, in
particular
• This was finalized by assessment of their
potential in fractionation processes
Scheme 1. Strategy for academic development of novel and effective ionic liquids.
55
4. Results
4.1 Switchable Ionic Liquid Fractionation
current kraft process, in which they are burnt
for energy recovery.
The main objective of the work was to develop a process to fractionate the main biomass
The SILs were synthesized by bubbling CO2 or
components to enable their utilization in the
SO2 through the liquid mixture with the ratio
production of materials, chemicals and fuels
of amidine/guanidine to hydroxyl-containing
for the future bioeconomy.
compound calculated based on the number of
hydroxyl groups in the alcohol or alkanol. Here
Several Switchable Ionic Liquids (SIL) were
a sample case is presented as an example
synthesized and characterized. The prepared
procedure. DBU-MEA-SO2-SIL was prepared
SILs were used in a novel process involving the
by passing SO2 through the mixture containing
fractionation of Nordic woody biomass by se-
1:1 molar amounts of 1,8-diazabicyclo-[5.4.0]-
lective dissolution. The process was discov-
undec-7-ene (DBU) and monoethanolamine
ered and extensively developed during the
(MEA). The weight increase with the SIL
FuBio programme, with the duration of frac-
corresponds to a molar ratio of 1:1:1 of all
tionation successfully reduced from five days
components. These results indicate that all
to just two hours. In addition, relatively high
OH groups of the MEA react upon formation
purity of the resulting fractions was achieved;
of the ionic liquid according to Scheme 2. This
for example, cellulose-rich material contain-
observation is supported by NMR and FTIR
ing 79 wt-% cellulose, 11 wt-% hemicelluloses
studies.
and 5 wt-% lignin was obtained from spruce
chips. All of the produced fractions were char-
In previous studies it has been demonstrated
acterized in detail using several methods.
that SILs are potential novel solvents for the
The SIL treatment enables the fractionation
fractionation of lignocellulosic material into
of biomass into relatively pure fractions un-
suitable fractions. However, the fractionation
der milder conditions than in current industri-
efficiency has not been comparable to those
al processes, thus consuming less energy. The
obtained with conventional ILs mainly due to
process could be utilized where the production
the low treatment temperature. Therefore,
of hemicelluloses and lignin together with cel-
the fractionation of lignocellulosic material
lulose fibres is targeted. Hemicelluloses and
was investigated based on new types of
lignin fractions could be processed further as
SILs. These were based on glycerol or alkanol
bio-based chemical and materials, thus adding
amine, CO2 or SO2 and an amidine (DBU).
value to these raw materials compared to the
The new SILs have one major advantage
Scheme 2. Proposed reaction scheme for the formation of DBU-MEA-SO2-SIL (adapted from Anugwom
et.al. 2014. ChemSusChem 7, 1170).
56
compared to previously presented SILs: their
filtration. The undissolved wood material
decomposition temperatures are significantly
was washed several times with isopropanol
higher,
at about 40°C until all the SIL was visually
thus
allowing
higher
treatment
temperatures, which leads to more efficient
removed.
fractionation. Wood was fractionated without
of wood, the undissolved residues as well
any
normal
as precipitated materials from the SIL were
pressure and at 100-120°C. However, the
analysed by various methods. Weight losses
treatment time was found to be too long
were recorded and the materials were analysed
and too cost-intensive to implement at an
in order to determine their composition. The
industrial scale. Furthermore, the use of large
latest results showed that the STHT method
amounts of SILs and the need for drying
can be used to remove almost all lignin and
of the wood raw material would also add to
the majority of hemicelluloses from wood
the process cost. However, addition of water
in just two hours. For example, DBU/MEA/
to the wood/SIL mixture or/and use of fresh
CO2-water treated spruce contained 79 wt-%
non-dried wood was found to be effective in
cellulose, and only 11 wt-% hemicelluloses and
reducing SIL consumption. The optimization
5 wt-% lignin. In addition, the resulting fibres
of conditions for the selective fractionation
are very light in colour (Figure 1).
mechanical
agitation
under
After
the
dissolution/extraction
of woody biomass was investigated via a
novel and economically feasible fractionation
Significant further improvements to the process
method using an alkanol amine (MEA) and
can be made. Firstly, the recovery of dissolved
an organic superbase (DBU) derived SIL with
hemicelluloses and lignin from the spent SIL
water. The Short Time High Temperature
should be improved. In addition, the process is still
(STHT) approach was used, where the wood
far from optimized, thus, substantially improved
was immersed in the SILs and water added
results could be achieved through optimization.
to achieve a 1:3:5 weight ratio. The mixture
Furthermore, the number of new SIL designs is
was kept at 160°C under normal atmospheric
considerable and remains so far unexplored.
pressure for 2 hours without stirring. While
Most importantly, SILs ‘triggered’ with acid gases
the mixture was still hot, the undissolved
other than those studied here could give rise to a
wood fraction was separated using vacuum
rich family of yet unknown potential.
Figure 1. Undissolved fluffy material recovered from A) birch and B) spruce after SIL treatment applying
the STHT method. The SIL applied was DBU-MEA-SO2 with water at 160°C for 2 h.
57
4.2 Recyclable Ionic Liquid Design
[P8881][OAc], which was demonstrated to be
phase-separable upon addition of water or
Throughout FuBio 1 & JR2, emphasis was placed
kosmotropic electrolyte solutions (e.g. sodium
on the development of recyclable systems
acetate solution), was also found to be an excellent
for biomass processing at the University of
solvent for cellulose as the DMSO electrolyte. Its
Helsinki. The motivation for this was that no
ability to form isotropic solutions was so strong
workable strategies were available for recycling
that it was possible to obtain 1H-13C heteronuclear
ionic liquids after a fractionation step. Typically,
single-quantum correlation (HSQC) NMR spectra
oligomeric
are
where the cellulose backbone was free from any
present that are very difficult to remove due
ionic liquid resonances (Figure 4). To the best of
to the non-volatility of traditional ionic liquids.
our knowledge, this was the first time that this
Therefore, we sought to introduce recyclability
has been achieved with high DP cellulose (MCC).
to the ionic liquid in the form of the classical
Moreover, we were able to assign the terminal
purification methods of distillation and phase
glycosidic C1 and anomeric C1 signals from the
materials
and
inorganics
separation (Figure 2). In this case the distillation
chain ends in the 1H NMR spectra (Figure 5).
of [TMGH][CO2Et] required 130°C and 5 mbar in
Cellulose regenerated from this solution mainly
a Kugelrohr. In the case of recycling by phase-
as the more thermodynamically stable cellulose
separation, dissolved cellulose and [P8881][OAc]
II crystalline polymorph, together with some
could be recovered by addition of pure water
residual cellulose I and amorphous cellulose
or kosmotropic salts. [P8881][OAc] could then be
(Figure 4). Therefore, these are highly suitable
reused in the dissolution of cellulose.
media for further biomass pre-treatments,
fractionations or chemical modification. This
After
continued
optimization
of
different
will be thoroughly investigated in the future.
distillable acid-base conjugate ionic liquids for
biomass processing, it was found that [DBNH]
[OAc] was a highly effective ionic liquid for
cellulose dissolution. This was a result of the
very low viscosity achieved by the combination
of
1,5-diazabicyclo(4.3.0)non-5-ene
(DBN,
superbase) and acetic acid (organoacid), which
was similar to that of the benchmark ionic
liquid [emim][OAc] (Figure 3). When combining
different bases with acetic and propionic acid,
a clear trend developed concerning cellulose
solubility. Combinations of these acids with the
superbase range proved effective at dissolving
cellulose, whereas their combination with
normal organic bases was ineffective. This
was rationalized by the fact that the basicity
of the unconjugated base is also a measure
of the ionic liquids’ cation acidity. It was
concluded that if the cations are too acidic
they stabilize the anion to such an extent that
solvation of cellulose, with significant enthalpy
of dissolution gain through cellulose hydrogen
bond breakage, is inhibited.
58
a)
b)
Figure 2. Distillation of the cellulose-dissolving [TMGH][CO2Et] (a) and the recycling strategy for phaseseparable ionic liquids, such as [P8881][OAc] (b), which dissolve cellulose as their DMSO electrolytes (Adapted
from King et al. 2011, Angew. Chem. Int. Ed. 50, 6301 and Holding et al. 2014. ChemSusChem 9, 1565).
59
a)
b)
c)
Figure 3. Viscosities vs. temp. of a range of acid-base conjugate ionic liquids (a), with [DBNH][OAc]
having the same viscosities as the benchmark [emim][OAc]. X-ray crystal structure of [DBNH][OAc] (b)
indicating strong hydrogen bonding between anion and cation. Proposed model for how cation acidity
influences the enthalpy gain for Gibbs free energy of dissolution (c). (Adapted from Parviainen et al. 2013
ChemSusChem 6, 2161).
a)
b)
Figure 4. (a) Solution-state HSQC NMR of MCC dissolved in [P8881][OAc]:d6-DMSO. (b) XRD of untreated
and regenerated MCC (adapted from Holding et al. 2014. ChemSusChem 9, 1565).
Figure 5. Assigned 1H NMR of MCC dissolved in [P8881][OAc]:d6-DMSO showing polymeric and terminal
C1 peaks.
60
4.3 Homogeneous Ionic Liquid-Aided
Fractionation
Without autohydrolysis, 7% of birch was insoluble. Thus, after autohydrolysis (P-factor
500) the purity of precipitate 1 increased sig-
The objectives of this task were to define ad-
nificantly (LIG/CH = 0.27 to 0.16) without loss
equate pretreatments to enhance IL frac-
of cellulose yield or molar mass.
tionation of wood components and to define
quantitative measures of IL’s wood polymer
The process was repeated with different
solvation capability. We employed a standard
particle sizes and P-factors. Compared to <125
process, explained in Figure 6, to investigate
µm Wiley meal, more insolubles were produced
the effects of pretreatments.
with commercial sawdust, but this could be
compensated by increasing the autohydrolysis
Comparing native and autohydrolyzed birch,
P-factor from 500 to 1500. In order to fragment
the latter produced better results (Figure 7).
the remaining lignin, ozonation was applied on
Figure 6. Standard fractionation scheme for optimization of processing conditions.
a)
b)
Figure 7. (a) ILAF of wood; (b) ILAF of autohydrolyzed wood.
61
autohydrolyzed wood. However, no increased
hemicellulose selective dissolution window,
selectivity in terms of molar mass or solubility
as illustrated in Figure 8. Maximum removal
was gained.
of xylan is at the border line between the
selective and unselective areas of the chart.
A final cellulose II pulp with a lignin content of
When the molar fraction of water exceeds a
13% was thus produced. On centrifugation, the
certain threshold value, hemicelluloses are no
pulp compacted into a form containing 96%
longer soluble in the system. This means that
water, which oven-dried to a black, hard sol-
the water can also be used to regenerate the
id. As is, the pulp could be blended with card-
dissolved material.
board pulp to potentially reduce porosity. With
further conventional delignification, dissolving
As a result of testing several ionic liquid systems
pulp could be produced.
and different sources of pulps for optimizing
IONCELL-P fractionation, it can be reported
4.4 IONCELL-P Process
that fractions separated in optimal conditions
(3h, at 60˚C, water content dependent on used
The objective of this research task was to define
ionic liquid system) have no molecular weight
the optimal conditions for the quantitative
degradation, have high recovery yields of
fractionation of paper grade pulps using the
fractionated polysaccharides, and maintain the
IONCELL-P(ulp) process in order to upgrade
cellulose I crystallinity of the cellulose fraction.
them to acetate grade or dissolving pulps. The
study was based on the differences in solubility
The
behaviour of cellulose and xylan in ionic liquid
concluded to be successful, since it has
systems. Different co-solvents mixed with the
been shown that high yields and high purity
ionic liquid alter the ionic liquid’s dissolution
polymeric components can be retrieved from
abilities to different levels. Water addition
the IONCELL-P fractionation processes, with
deteriorates
the
the
ionic
liquid’s
dissolution
pulp
extraction
cellulose
fractions
processes
having
can
be
promising
abilities. When a sufficient amount of water is
properties to enter the market for value-added
added, the solvent system enters a so-called
acetate grade pulps.
a)
b)
Figure 8. Selective hemicellulose dissolution window of [emim][OAc] as a function of ionic liquid, water
and pulp content as weight %. The selective dissolution window is highlighted dark blue (a). Molar mass
distributions (b): of the initial birch kraft pulp, the separated cellulose fraction (blue), the precipitated
hemicellulose fraction (red), and the calculated sum of the fractions (treatment, 15 wt % water, 60°C, 3
h; consistency, 10.5 wt %).
62
4.5 Cellulase Modification of Cellulose in
Ionic Liquid
DMP and [EMIM]AcO, two cellulose-dissolving
ILs, were very basic in aqueous solution and,
thus, the medium basicity appeared a plausible
Ionic liquids (ILs) dissolve cellulose. This
reason for the observed enzyme inactivity.
opens up new interesting opportunities for
Studies on enzymatic cellulose hydrolysis in
modifying
chemically
different basic solutions without IL, as well as
cellulose
physically,
cellulose
studies with alkaline cellulases, did not, however,
modifications in IL solutions have so far
support the theory of IL basicity being a major
not been studied significantly. The benefits
contributor to enzyme inactivation. On the other
of using enzyme catalysis include, e.g.,
hand, cellulase thermostability appeared to
mild reaction conditions leading to energy
correlate with higher hydrolytic performance in
savings and less product degradation, and
IL solutions. In the programme, novel cellulose-
highly specific reactions meaning fewer by-
dissolving and distillable ILs based on the TMG
products as compared to chemical reactions.
and DBN superbases were developed. The
With different enzymes it could be possible to
cellulase-compatibility of these ILs was tested,
catalyse oxidation, hydrolysis, acylation and
but thee ILs were found not to offer any increased
other cellulose modifications in ILs. In FuBio
cellulase activity compared to other IL types.
JR2 WP2, enzyme work was concentrated on
Analysis of saccharide content in IL solutions
studying the action of glycosyl hydrolases,
was found to be difficult when developing a
mainly endoglucanases, in cellulose hydrolysis
capillary electrophoresis method for the analysis
in aqueous ILs. By designing functional
of oligosaccharides tolerating the presence of IL.
and
enzymatically.
Enzymatic
combinations of glycosyl hydrolases and ILs,
new concepts can be considered for tailoring
Radiolabeled
pulp properties (e.g. controlling DP and
study their cellulose-binding capability in
cellulases
were
used
to
removing hemicelluloses) and for the total
IL solutions (Figure 9). The binding studies
hydrolysis of plant cell wall polysaccharides to
were done pairwise with intact cellulases
monosaccharides in the production of biofuels
and their core domains, i.e. cellulases lacking
and biochemicals.
a carbohydrate-binding module (CBM). The
results clearly show the cellulose binding
Cellulases are severely inactivated by cellulose-
to be sensitive to IL presence. CBM binding
dissolving ILs. In this study, the reasons for
was found to be highly IL-sensitive, whereas
cellulase inactivation were studied in detail. At the
cellulose binding through the active site tunnel
beginning of the study, it was noticed that [DMIM]
in cellobiohydrolases was much less affected
Figure 9. Binding isotherms for Trichoderma reesei endoglucanase Cel5A (A), cellobiohydrolase Cel7A (B)
and the core domain of Cel7A (C) in five different ionic liquid media.
63
by ILs. Endoglucanases were found to be very
glycerol switchable ionic liquid (SIL) systems.
dependent on their CBM for cellulose-binding,
In addition to the experimental work, thermal
which translated into a high IL sensitivity.
separation processes for ionic liquid (IL)
recycling in biomass fractionation processes
Although cellulases were generally inactivated
using ionic liquids as fractionating agents
in IL solutions, the IL [DMIM]DMP was found to
were modelled.
be stabilizing for cellulases during prolonged
incubation
were
The Knudsen effusion apparatus is depicted
found to reduce the DP of partially dissolved
periods.
Endoglucanases
in Figure 10. Initial tests were carried out.
microcrystalline cellulose in 90% [DMIM]
The apparatus is effective for measuring
DMP, representing a new cellulase activity on
compounds with very low vapour pressures
dissolved, non-derivatized cellulose.
(e.g. aprotic ionic liquids).
4.6 Thermodynamics and Modelling of
Ionic Liquid Distillation
The measurement results indicate that DILs can
be distilled at pressures below 45 mbar without
significant decomposition. Distillation at lower
The work done consisted of Knudsen effusion
pressures and temperatures decreased the
apparatus
pressure
decomposition of DILs. In addition, pure DBN
[DBNH]
was regenerated, possibly from hydrolysis
[CO2Et] and [DBNH][OAc] distillable ionic liquids
products of DBN, which may have an important
(DILs), distillation experiments of [DBNH]
role in improving process feasibility. In the
[OAc] + water mixture and phase equilibrium
distillation experiments, the DIL was purified
measurements and modelling of CO2 + DBU +
to 90 m-% purity, without further optimization.
construction,
measurements
of
vapour
[TMGH][CO2Et],
The structure of CO2 + DBU + glycerol SILs was
highly dependent on the DBU:glycerol ratio. SIL
systems were stable in the 30-80°C temperature
range. Addition of water into the system caused
formation of competing CO2 + DBU + H2O SIL.
Figure 10. Schematic of the Knudsen effusion apparatus: a) wide range gauge; b) turbo pump Edwards
STPA 1303C; c) scroll pump XD510; d) gate valve; e) cold finger for liquid nitrogen; f) ball valve; g)
air admittance valve; h) gas admittance valve; i) vacuum chamber; j) aluminium blocks (ovens); k)
temperature panel Nokeval; l) PID temperature controllers; m) computer.
64
For modelling the recovery processes of
were examined. Membrane filtration of these
ILs, three promising ILs having water as
ILs is challenging, mainly due to their high
the
[emim]
viscosity. This can be overcome either by using
[OAc]; 2) a distillable ionic liquid formed from
low-viscosity co-solvents, such as molecular
1,1,3,3-tetramethylguanidine
solvents
antisolvent
were
chosen:
and
1)
propanoic
(methanol,
ethanol,
isopropanol,
acid; 3) a switchable ionic liquid formed from
etc.), or by performing filtrations at elevated
1,8-diazabicyclo[5.4.0]undec-7-ene and butanol.
temperatures. As very high temperatures
The modelling of the chemical systems relied
cannot be used with polymeric membranes,
on various estimation methods for modelling
ceramic
physical property, VLE and energy variables. The
However, ceramic membranes offer restricted
simulated pressure levels and the presence of
cut-off options at the nanofiltration scale. After
reactions in the chemical systems indicate short-
identifying suitable membranes and proving
path distillation in the technical implementation
their usability with the ILs, the final step
of the recovery processes of ILs.
involved trials with real residue solutions of the
membranes
were
also
tested.
ILs. The NF270 nanofiltration membrane and
4.7 Membrane Purification of Ionic
Liquids
TiO2 ceramic nanofiltration membranes were
tested with real residues and the results were
very positive: good retentions for sugar-like
The focus of this study was on the recovery
organics were gained with these membranes for
and recycling of Ionic Liquids (ILs) by pressure-
both ILs in the studied conditions (see Figure 11
driven membrane separation processes. ILs
below for [emim][DMP] residue). The separation
were used for processing whole wood. First,
processes can also be optimized for better
the filterability and tolerance of selected
performance through optimal combinations of
membranes towards [emim][DMP] (IL) and
parameters such as temperature, cross-flow
DBU-MEA-SO2 (Switchable Ionic Liquid, SIL)
velocity and pressure.
a)
b)
Figure 11. a) Flux of [emim][DMP]-Isopropanol (1:4) solution through the ceramic Inopor®ultra TiO2
membrane (mean pore size 5 nm, cut-off 8500 g/mol) showing the retention of saccharides at different
times during the test. Batch 2 L, Δp 3 bar, temperature 30°C, cross-flow velocity 0.8 m/s, filtration area
1040 cm2 and VRF = 2.0. b) The filter unit for high-pressure cross-flow filtrations showing the module for
polymeric flat sheet membranes. Inset: module with ceramic membrane.
65
5. Exploitation plan and impact
of results
Our academic understanding of the area
due to their relative novelty. Therefore, much
has developed to a very high level, and is
effort has been targeted at understanding
reflected in the quality of the publications
these enigmatic structures and the phenomena
produced.
have
that they present. To achieve future success in
been presented, with both SIL fractionation
this area, work should be focused on selected
and the IONCELL-P process representing
target processes and sufficient resources
highly promising methods of wood and pulp
for continued research should be continued
fractionation (respectively). Three new classes
as new unique effects and phenomena are
of recyclable ionic liquids, switchable (SILs),
constantly
distillable (DILs) and phase-separable (PSILs),
media that are not present or achievable with
are being developed, which should be placed
molecular solvents.
Several
new
processes
being
discovered
with
these
in their appropriate applications in future
work. All three are known to dissolve cellulose.
Switchable ionic liquid (SIL) fractionation
SILs are best understood in regard to wood
and the IONCELL-P process offer interesting
fractionation to produce high-purity cellulose
avenues
through extraction of lignin and hemicellulose.
fractionation clearly needs further work to
DILs and PSILs are known superb solvents for
demonstrate full recyclability of the system,
cellulose, although their ability to fractionate
as this was only partly touched upon during
wood is less studied. Cellulase enzyme activity
the
is reduced in ionic liquids but not destroyed.
pulp quality will also likely emerge as a
Mechanistic understanding of this process
result of this development. The IONCELL-P
is being developed and further studies are
process, as the simplest process studied,
planned. Methodologies and equipment for
is
studying and modelling the thermodynamics of
techno-economic studies would be useful
ionic liquid recycling are also being developed,
to refine these processes further. To reduce
as are those for membrane purification of the
research costs and enable up-scaling, future
used ionic liquid. For those membranes that
programmes should establish protocols for
are stable in ionic liquids, unoptimized cross-
the recycling and reuse of ionic liquids under
flow nanofiltration of the used ionic liquid
study. Investment in equipment judiciously
demonstrated reasonable fluxes and good
located
saccharide retention. Important progress by
would facilitate this and the development of
international standards has been made in
competence in this area.
for
project.
already
in
future
development.
Improvements
quite
the
mature.
in
More
appropriate
SIL
recovered
detailed
departments
the area of the processing of lignocellulosics
using ionic liquids, and the potential of this
area of research is clear. Further academic
understanding and process optimization are
clearly needed to prove the use of ionic liquids
for wood fractionation.
In contrast to our understanding of molecular
solvents, the area of ionic liquids is a highly
demanding area with more complex chemistry
66
6. Networking
different
work. These included Tom Welton and Jason
partners and international research groups
Hallet from Imperial College, Seema Singh from
was encouraged during the project. Two
the Joint Bioenergy Institute, Roberto Rinaldi
international symposia were organized on the
from the Max Planck Institute for Coal Research,
topic of the work package. One was held in May
Joern Viell from AVT-Aachen and Martin Lawoko
2012 at Haikko Manor, Porvoo, and one in August
from the Wallenberg Wood Science Centre.
Close
collaboration
between
the
2013 at the University of Helsinki. Respected
international researchers in the area of ionic
Table 1 shows both the partners and their role
liquids and biomass processing presented their
in the work package.
Table 1: Work package partners and their roles
Role of the participating organisation
Aalto University
(FPT) IONCELL-P Process, Homogeneous IL-aided
• Forest Products Technology (FPT)
fractionation,
• Biotechnology and Chemical
(BCT) Thermodynamics and Modelling of Ionic Liquid
Technology (BCT)
Distillation
Andritz
Industrial tutor
Lappeenranta University of
Membrane Purification of Ionic Liquids
Technology
Metsä Fibre
Stora Enso
Industrial tutor
WP leader. Recyclable Ionic Liquid Design
UPM-Kymmene
Industrial tutor
VTT
Cellulase Modification of Cellulose in Ionic Liquids
Switchable Ionic Liquid Fractionation
67
7. Publications
Anugwom, I., Eta V., Mäki-Arvela, P., Virtanen,
Ebner, G., Vejdovszky, P., Wahlström, R., Su-
P., Hedenström, M., Hummel, M., Sixta, H. and
urnäkki, A., Schrems, M., Kosma, P., Rosenau,
Mikkola, J.-P. 2014. Switchable Ionic Liquids as
T. and Potthast, A. 2014. The effect of 1-ethyl-
Delignification Solvents for Lignocellulosic Ma-
3-methylimidazolium acetate on the enzymat-
terials. ChemSusChem 7, 1170-1176.
ic degradation of cellulose. Journal of Molecular Catalysis B: Enzymatic 99, 121-129.
Anugwom, I., Eta, V., Mäki-Arvela, P., Virtanen, P., Hedenström, M., Ma, Y., Hummel,
Eta, V., Anugwom, I., Virtanen, P., Eränen, K.,
M., Sixta, H. and Mikkola, J.-P. 2014. Towards
Mäki-Arvela, P. and Mikkola, J.-P. 2014. Loop
optimal selective fractionation for Nordic
vs. batch reactor setups in the fractionation
woody biomass using Novel Amine–Organ-
of birch chips using switchable ionic liquids.
ic Superbase derived Switchable Ionic Liquid
Chemical Engineering Science 238, 242-248.
(SIL). Manuscript Submitted.
Eta, V., Anugwom, I., Virtanen, P., Mäki-Arvela,
Anugwom, I., Eta, V., Mäki-Arvela, P., Vir-
P. and Mikkola, J.-P. 2014. Enhanced mass trans-
tanen, P., Lahtinen, M. and Mikkola, J.-P. 2014.
fer upon switchable ionic liquid mediated wood
The composition and crystallinity of birch
fractionation. Industrial Crops & Products 55,
chips (Betula pendula) upon 'DBU-DEA-CO2-
109-115.
SIL' alkanol amine - organic super base - derived Switchable Ionic Liquid (SIL) treatment.
Froschauer, C., Hummel, M., Iakovlev, M., Ro-
Green Processing & Synthesis 3, 147-154.
selli, A., Schottenberger, H. and Sixta, H. 2013.
Separation of Hemicellulose and Cellulose from
Anugwom, I., Mäki-Arvela, P., Virtanen, P.,
Wood Pulp by Means of Ionic Liquid/Cosolvent
Damlin, P., Sjöholm, R. and Mikkola, J.-P. 2011.
Systems. Biomacromolecules 14, 1741-1750.
Switchable Ionic liquids (SILs) based on glycerol and acid gases. RSC Advances 1, 452-457.
García, V., Valkama, H., Sliz, R., King, A. W.
T., Myllylä, R., Kilpeläinen, I. and Keiski, R. L.
Anugwom,
I.,
Mäki-Arvela,
P.,
Virtanen,
2013. Pervaporation recovery of [amim]Cl dur-
P., Willför, S., Sjöholm, R. and Mikkola, J.-
ing wood dissolution; effect of [amim]Cl prop-
P. 2011. Treating birch wood with a switchable
erties on the membrane performance. Journal
1,8-diazabicyclo[5.4.0]-undec-7-ene-glycerol car-
of Membrane Science 444, 9-15.
bonate ionic liquid. Holzforschung 66, 809-815.
Hauru, L. K. J., Hummel, M., King, A. W. T.,
Anugwom, I., Mäki-Arvela, P., Virtanen, P.,
Kilpeläinen, I. and Sixta, H. 2012. New insights
Willför, S., Sjöholm, R. and Mikkola, J.-P. 2012.
into the requirements for dissolution of cellu-
Selective extraction of hemicellulose from
lose into ionic liquids. Biomacromolecules 13,
spruce with Switchable Ionic liquids. Carbohy-
2896−2905.
drate Polymers 87, 2005-2011.
68
Hauru, L. K. J., Ma, Y., Hummel, M., Alekhi-
King, A. W. T., Parviainen, A., Karhunen, P.,
na, M., King, A. W. T., Kilpeläinen, I. A., Pent-
Matikainen, J., Hauru, L. K. J., Sixta, H. and
tilä, P. A., Serimaa, R. and Sixta, H. 2013. En-
Kilpeläinen, I. 2012. Relative and inherent nu-
hancement of ionic liquid-aided fractionation
cleophilicity/basicity/diffusivity of imidazoli-
of birchwood. Part 1: Autohydrolysis pretreat-
um-based ionic liquids – the implications for
ment. RSC Advances 16365-16373.
lignocellulose processing applications. RSC
Advances 2, 8020-8026.
Holding, A. J., Heikkilä, M., Kilpeläinen, I. and
King, A. W. T. 2014. Phase-separable ionic liq-
King, A. W. T., Xie, H., Fiskari, J. and Kilpeläin-
uids and electrolytes for biomass processing.
en, I. Reduction of biomass recalcitrance via bi-
ChemSusChem 9, 1565-1577.
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Biofuels, World Scientific Publishing, Ed. Arthur
Hummel, M., Froschauer, C., Laus, G., Röder,
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T., Kopacka, H., Hauru, L. K. J., Weber, H. K.,
Sixta H. and Schottenberger H. 2011. Dimethyl
Kyllönen, L., Parviainen, A., Deb, S., Lawoko,
phosphorothioate and phosphoroselenoate
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ionic liquids as solvent media for cellulosic ma-
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Green Chemistry 15, 2374-2378.
Hyväkkö, U., King, A. W. T. and Kilpeläinen, I.
Leskinen, T., King, A. W. T. and Argyropou-
2014. Extraction of wheat straw with aqueous
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tetra-n-butylphosphonium hydroxide. BioRe-
terials with ionic liquids; Production of biofuels
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and chemicals with ionic liquids, Springer Book
Series - Biofuels and Biorefineries, Ed. Zhen
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Vaher, M., Kaljurand, M. and Koel, M. 2014.
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Leskinen, T., King, A. W. T., Kilpeläinen, I. and
media obtained from lignocellulosic biomass:
Argyropoulos, D. S. 2013. Fractionation of lig-
Comparison of capillary electrophoresis and
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Ostonen, A., Sapei, E., Uusi-Kyyny, P., Kle-
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2012. Partial Enzymatic Hydrolysis of Micro-
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diazabicyclo-[5.4.0]-undec-7-ene
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2, 4472-4480.
Parviainen, A., King, A. W. T., Mutikainen, I.,
Wahlström, R., Rovio, S. and Suurnäkki, A.
Hummel, M., Selg, C., Hauru, L. K. J., Sixta, H.
2013. Analysis of Mono- and Oligo-saccharides
and Kilpeläinen, I. 2013. Predicting cellulose
in Ionic Liquid Containing Matrices. Carbohy-
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Rauhala, T., King, A. W. T., Zuckerstatter, G.,
Suuronen, S. and Sixta, H. 2011. Effect of autohydrolysis on the lignin structure and the kinetics of delignification of birch wood, Nordic
Pulp & Paper Research Journal 26, 386-391.
Roselli, A., Hummel, M., Monshizadeh, A.,
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extraction method for upgrading eucalyptus
kraft pulp to high purity dissolving pulp. Submitted to Cellulose.
Stépán, A. M., King, A. W. T., Kakko, T., Toriz,
G., Kilpeläinen, I. and Gatenholm, P. 2013. Fast
and highly efficient acetylation of xylans in
ionic liquid systems. Cellulose 20, 2813-2824.
Wahlström, R., King, A. W. T., Parviainen, A.,
Kruus, K. and Suurnäkki, A. 2013. Cellulose
hydrolysis with thermo- and alkali-tolerant
cellulases in cellulose-dissolving superbase
ionic liquids. RSC Advances 3, 20001-20009.
Wahlström, R., Rahikainen, J., Kruus, K. and
Suurnäkki, A. 2014. Cellulose hydrolysis and
binding with Trichoderma reesei Cel5A and
Cel7A and their core domains in ionic liquid solutions, Biotechnology & Bioengineering 111,
726-733.
70
HYDROXY ACIDS
(AND OTHER ACIDS)
FROM BLACK LIQUOR
ADVANCED SEPARATION TECHNOLOGIES
POLYMERIZATION OF HYDROXY ACIDS
BIOTECHNICAL PRODUCTION OF GLYCOLIC ACID
CONTACT PERSON – Work Package 6 leader Jarmo Ropponen, [email protected]
Hycail: Svante Wahlbeck
Kemira: Jukka Hietala
Metsä Fibre: Ismo Reilama
Lappeenranta University of Technology: Sanna Hellstén, Mari Kallioinen, Jussi Lahti,
Mika Mänttäri, Tuomo Sainio
University of Helsinki: Sari Rautiainen, Timo Repo
University of Jyväskylä: Raimo Álen, Pauli Moilanen
UPM-Kymmene: Päivi Varvemaa
VTT Technical Research Centre of Finland: Thomas Gädda, Sakari Kaijaluoto,
Katariina Kemppainen, Outi Koivistoinen, Klaus Niemelä, Minni Pirttimaa, Peter Richard
72
ABSTRACT
The purpose of this study was to develop technologies and competences to recover
hydroxy acids from black liquor and produce glycolic acid biotechnically from sugars.
A novel multistep separation process for recovering hydroxy acids from black liquor,
combining membrane filtration, chromatographic separation and electrodialysis, was
developed. Further polymerization of the hydroxy acids was also conducted to evaluate
their properties as value-added products. The results suggest that in the demonstrated
process the neutralization of black liquor is not required, and that the purity of the end
product is suitable for polymerization. In addition, the study demonstrates for the first time
the conversion of purified hydroxy acid mixtures obtained from black liquor to polymeric
material. Furthermore, production of 17 g/l of glycolic acid was achieved by fermentation
of the engineered Kluyveromyces lactis strain. Development of bioreactor cultures and
the selection of a suitable yeast host led to improvements in production levels that
demonstrate technical feasibility. The results identify black liquor as an untapped source
of hydroxy acids which can be further developed into value-added products.
Keywords:
hydroxy acids, separation, polymerization, biotechnical production
73
1. Background
chromatography,
membrane
and
processes
steps.
a
combination
with
of
precipitation-
Globally, more than 140 million tonnes of wood
crystallization
kraft pulp and 20 million tonnes of non-wood
was made in each of these areas, resulting
kraft and soda pulps are produced each year.
in a number of potential process concepts
Only a fraction of the dissolved organic matter
for further optimization and development.
originating from this production – including
In order to achieve reasonable amounts of
tall oil (1.4 million tonnes), turpentine (200 000
hydroxy acids to enable practical application
tonnes) and kraft and soda lignin (100 000
evaluations, efforts were focused on developing
tonnes) – is currently isolated as pulping by-
a multistep separation and purification process
products for chemical or material applications.
encompassing
The spent cooking liquor from kraft pulping, or
purification methods.
all
of
Significant
the
progress
abovementioned
‘black liquor’, consists mainly of lignin and wood
extractives, but also contains salts of hydroxy
carboxylic acids, which are formed from wood
2. Objectives
carbohydrates in alkaline conditions during
pulping. All black liquors contain varying
The main objective was to design a novel
amounts of glycolic, lactic, 2-hydroxybutanoic,
value chain based on hydroxy acids separated
2,5-di-hydroxypentanoic, xyloisosaccharinic,
from black liquor or biotechnically produced
and glucoisosaccharinic acids as the main
from sugars. These hydroxy acids would
hydroxy acids, in addition to numerous minor
be converted into novel biopolymers and
ones. The formation of hydroxy acids may
developed and tested for the technologies
account for up to 10–15% of wood raw material
needed to enable such a value chain in reality.
consumption in pulping. Their isolation as new
The specific aims were to develop:
pulping by-products has not been realized
at the mill scale to date due to a number of
technical challenges as well as limited markets
for many compounds. The annual production
of these hydroxy acids in kraft pulping is
approximately 6 million tonnes in Europe
• Concept for the separation of organic acids
from black liquor
• Fermentation-based technology for the
production of glycolic acid
• Potential applications for these organic acids
alone, representing a vast underutilized raw
material source. Hydroxy acids are building
block chemicals which could be widely utilized
3. Research approaches
in the synthesis of a range of chemicals and
polymeric materials as replacements for
As there were no existing feasible separation
fossil-derived materials. Potential spearhead
processes for the recovery and purification
applications include biodegradable plastics,
of hydroxy carboxylic acids from black liquor
packaging films, adhesives and cosmetics.
to serve as a starting point, the research
approach in process development was strongly
74
Most previous studies addressing the isolation
experimental in nature. It was concluded early
of hydroxy acids from black liquors deal
on that a multistage separation process will be
with isolation in small volumes for analytical
needed due to the complexity of the feedstock
purposes. In the FuBio programme, three
and the high purity requirements of the final
approaches for larger-scale isolation of hydroxy
product. The majority of process development
acids
was conducted using authentic soda black
were
investigated:
electrodialysis,
liquor instead of kraft black liquor mainly for
4. Results
safety reasons. The selection of ultrafiltration
modules
and
membranes,
however,
was
carried out with kraft black liquor. Experiments
with synthetic solutions were also carried out
4.1 Separation process for recovery and
purification of organic acids from black
liquor
to investigate the most relevant separation
mechanisms in more detail.
A process sequence consisting of ultrafiltration,
size-exclusion chromatography, ion exchange,
Both hardwood (HW) and softwood (SW) soda
adsorption, and evaporation was successfully
black liquors were used. The main differences
implemented at laboratory scale (Figure 1) to
in the acid compositions of HW and SW
recover and purify a mixture of hydroxy acids
soda black liquors are the larger amount of
from black liquor. The purpose of the ultrafiltration
glucoisosaccharinic acid (GISA) in SW black liquor
stage was to remove the majority of lignin and
and the higher concentrations of 2-hydroxy
thus facilitate the subsequent chromatographic
butanoic acid and acetic acid in HW black liquor.
step, in which the carboxylic acids and NaOH
were separated from each other. The acids
These hydroxy acids offer many potential
were liberated using an ion exchange resin and
applications, e.g., as polymer precursors. As
concentrated by evaporation. Evaporation also
the separated hydroxy acids were obtained in
effectively eliminated volatile acids from the
acid form, polymerisations were carried out
hydroxy acid fraction. Finally, residual lignin was
using condensation polymerisation to obtain
removed by adsorption. Mixtures of hydroxy acids
polymeric materials. In addition, ring-opening
were obtained in high purity both from softwood
polymerisations were used to polymerize
and hardwood soda black liquors. An example of
glycolide produced from glycolic acid and
concentrations of individual acids and lignin after
benchmarked against commercial glycolide-
each process step is displayed in Figure 2.
based
polyglycolic
acid.
Moreover,
the
development of glycolic acid production based
on yeast fermentation was continued from the
first phase of the programme.
Figure 1. Separation process for recovering hydroxy carboxylic acids, volatile acids, and NaOH from black
liquor.
75
Figure 2. Typical average compositions of the hydroxy acid containing streams after each process step.
Removal of lignin and recovery of hydroxy acid
that the permeate of UP010 requires excessive
salts from soda black liquor
washing of the chromatographic column, and
Based on preliminary experiments, UP010 and
therefore the 1 kDa NP010 is recommended for
NP010 membranes with cut-off values of 10 kDa
ultrafiltration.
and 1 kDa, respectively, were chosen for more
detailed studies. Filtration experiments were
The concentrations of acids in the ultrafiltration
carried out with a rectangular cross-flow module
permeates are shown in Table 1. It was found
at a constant permeate flux of 70 kg/(m2h) and 40
that the hydroxy acids were well recovered in
kg/(m2h) until the pressure needed for constant
the permeate. For instance, more than 90%
flux increased to a predefined upper limiting value
of the isosaccharinic acids (softwood soda
(10 bar with UP010, 20 bar with NP010). With both
cooking liquor) were in the permeate stream (1
membranes, lower pressures were needed for
kDa, NP010 membrane) at a volume reduction
constant flux with softwood soda cooking liquor
of about 80%. Generally, acids retention was
than with hardwood cooking liquor.
very low or even negative. Due to the analytical
uncertainties,
In the filtration of hardwood soda black liquor,
small
differences
in
acid
concentrations are not meaningful.
lignin concentration decreased from 79.5 g/L
to 16.2 g/L when NP010 membrane was used
A significant purification of acids was achieved.
and to 32.6 g/L when using UP010 membrane.
For instance, the purity (based on total organic
The dry solids content decreased from 14.1
matter) of isosaccharinic acids increased from
wt-% to 9.0 wt-% using NP010 and to 10.4
20% to 40% when the softwood soda cooking
wt-% using UP010. For the softwood soda
liquor was filtered (1 kDa membrane). Purity
black liquor, the amount of lignin decreased
increase was caused by removal of lignin and
from 72 g/L to 14.6 g/L using NP010 membrane
probably also hemicelluloses. Only about 10%
and to 22.5 g/L using UP010. The amount of
of inorganic compounds (NaOH) were retained
dry solids decreased from 14.0 wt-% to 10.8
by the membrane.
wt-% with NP010 and 10.3 wt-% with UP010.
Subsequent chromatographic tests confirmed
76
Table 1. Concentrations of carboxylic acids based on CE analysis in the feed and in the ultrafiltration
permeates of NP010 and UP010 membranes in ultrafiltration of hardwood (HW) and softwood (SW) soda
black liquors.
XISA,
g/L
GISA,
g/L
2,5DHPA
g/L
2-OHLactic
butanoic acid,
acid,
g/L
g/L
HW Feed
3.2
7.3
1.1
4.0
NP010
2.8
6.8
0.9
4.4
UP010
4.5
6.0
0.8
SW Feed
3.7
15.7
1.3
NP010
4.4
18.3
UP010
4.9
18.7
Glycolic
acid,
g/L
Oxalic
acid,
g/L
Acetic
acid,
g/L
Formic
acid,
g/L
Total,
g/L
2.8
1.2
0.5
13.7
5.4
39.2
1.8
1.2
0.3
13.6
4.7
36.6
4.0
2.5
1.4
0.5
16.0
6.0
41.7
1.3
4.2
1.9
0.5
4.4
5.4
38.4
1.1
1.3
0.0
1.7
0.7
1.6
5.9
35.1
1.3
1.4
4.8
1.9
0.7
5.2
5.9
44.6
Chromatographic separation of hydroxy acids
overlaid on a photograph of the sample bottles
and sodium hydroxide
in Figure 3. NaOH elutes between approximately
The key step in the multistep separation
0.8 and 1.0 bed volume (fractions 7 and 8),
process developed here is chromatographic
whereas the hydroxy acids elute between 0.5
separation of hydroxy acids from the inorganic
and 0.8 bed volume (fractions 3 to 6).
compounds in black liquor. As no method
was available to conduct such a separation in
Some fractionation of the acids by size-
alkaline conditions, considerable efforts were
exclusion occurred in the Sephadex column,
invested in finding a suitable chromatographic
although this was not the main objective of
separation material for this purpose.
this separation step. Isosaccharinic acids elute
rapidly due to their large molecular size, and
After testing six different types of separation
therefore the largest concentrations were
media and several ionic forms of various ion
observed in fractions 3 and 4 obtained from
exchange resins, Sephadex G–10 size-exclusion
hardwood soda black liquor. Interestingly,
gel was found to be suitable for separating
dicarboxylic acids were also enriched in
hydroxy acids in the form of sodium salts from
fractions 3 and 4. Smaller 2-hydroxy butanoic
sodium hydroxide. A typical chromatogram, i.e.
acid was accumulated in fractions 5 and 6.
concentration history at the column outlet, from
GC/MS analysis also revealed the presence of
the separation of hardwood soda black liquor is
polar aromatic acids in fraction 6. Highest acid
Figure 3. Chromatographic separation of hydroxy acids and sodium hydroxide from ultrafiltration permeate
(NP010) of hardwood soda black liquor using Sephadex G–10.
77
concentrations were found in fractions 4 and
of hydroxy acids present. Injection volumes
5, while the concentration of acids in fraction
up to 24% were found to provide satisfactory
6 was very low. The total recovery yield of
purity of the hydroxy acids with respect to
hydroxy acids was 95% with the fractionation
sodium hydroxide. However, the concentration
scheme chosen. Similar results were also
of lignin in the hydroxy acid fraction increases
obtained for softwood soda black liquors.
with increasing injection volume.
It was further found that the recovery of
A series of 44 separation runs with hardwood
hydroxy acids from soda black liquor is possible
soda black liquor were conducted in the
also when the feed is concentrated to 25
Sephadex G–10 column to determine whether
wt-% dry solids. This is attractive, as a higher
the material is fouled by lignin. No shifts in
feed concentration markedly increases the
the retention times or concentration profiles
productivity of the process. Moreover, good
of the hydroxy acids and sodium hydroxide
separation was achieved with injection volumes
were observed in the conductivity and RI-
significantly larger than 8% of bed volume
signals, indicating that fouling does not affect
(Figure 4). This is because the elution of sodium
the separation of hydroxy acids and NaOH.
hydroxide slows down with increasing amount
On the other hand, the amount of lignin in the
Figure 4. Effect of injection volume on the separation of hydroxy acids from hardwood soda black liquor
using Sephadex G–10.
78
hydroxy acid fraction doubled during the 44
the pulp mill, this stream must be treated
consecutive cycles. This does not necessarily
separately, e.g. by electrodialysis.
pose major problems, as the residual lignin
can be effectively removed in the subsequent
Removal of residual lignin by adsorption
process steps.
Most of the lignin was precipitated from the
hydroxy acid fraction in the ion-exchange
The
the
stage. For example, from the hardwood
manufacturer for Sephadex G–10 is 2 to 13.
pH
range
recommended
by
soda black liquor the average lignin content
Therefore, its long-term stability in highly
decreased from approximately 3 g/L to less
alkaline conditions and elevated temperature
than 1 g/L. Removal of residual lignin was done
was investigated. Moisture retention capacity
by adsorption on a neutral hydrophobic polymer
is often used as a measure of effective cross-
resin (XAD–16). After adsorption treatment, the
link density in polymer gels. The changes in
lignin contents of the hardwood and softwood
the moisture retention capacity of Sephadex
soda black liquors were approximately 0.2 g/L
G–10 during 4 weeks exposure to 1 M NaOH at
and 0.1 g/L.
60 oC were below the experimental accuracy,
which suggests that its cross-link density was
No significant losses of hydroxy acids were
not significantly reduced. Nevertheless, two
observed during adsorptive lignin removal. The
unidentified compounds were observed in
yield of acids in the lignin removal step was
HPLC analyses of liquid phase samples after
96%. XAD–16 was thus concluded to be quite
aging of Sephadex G–10 in 1 M NaOH.
selective towards lignin over hydroxy acids.
Liberation of acids by ion exchange
Concentration by evaporation
Ion exchange with strong acid cation exchange
The hydroxy acid fractions were concentrated
resins was found to be suitable for liberation
by evaporation at reduced pressure after
of the acids (i.e. replacement of Na+ with H+).
the adsorption treatment step. The relative
The fractions obtained in the chromatographic
amount of volatile acids was reduced by
separation step were fed through an ion
40–70%. The final purity of hydroxy acids
exchange column packed with CS11GC resin in
was 38–91%. If higher purity is required
H+ form. The pH of the solutions collected at the
the product can be purified, for example by
column outlet after ion exchange ranged from 1.6
crystallization or chromatographic separation.
to 2.9. The conversion of sodium salts to acid form
The concentrations of the main components in
was 95–100% for all fractions. No loss of acids
the final products are presented in Table 2. In
due to adsorption to the stationary phase was
addition, GC/MS analysis revealed the presence
observed. The acid composition was unchanged,
of some glycerol and sugars (not shown).
with the exception that GISA is converted to its
lactone form due to the decrease in pH.
The final concentration could also be performed
using membrane filtration, provided that the
An aspect that deserves attention when
membrane can withstand acidic conditions
applying ion exchange for liberation of the
(initial pH 2, final pH approximately 1). Using
acids is the formation of sodium salts during
a suitable membrane, small volatile acids
regeneration of the resin. For example, if
could be separated in the concentration step.
sulphuric acid is used for regeneration, a
Concentration by membrane filtration is most
sodium sulphate stream is produced. To avoid
probably not feasible before liberation of the
disturbing the sodium–sulphur balance of
acids due to high lignin solubility at alkaline pH.
79
Further results on recovery and purification of
Recovery and liberation of carboxylic acids
hydroxy acids
by electrodialysis. Electrodialysis (ED) was
Further findings regarding the recovery and
investigated as an alternative method for
purification of hydroxy acids from black liquor
recovery and purification of hydroxy acids from
are described briefly below.
black liquor. It was noted that electrodialysis
membranes were chemically not very durable
Recommended ultrafiltration module. In order
against black liquor at any concentration,
to select an appropriate type of membrane
even when the solution pH was decreased
module for further studies, low shear rate (DSS)
by carbonation. This was mainly due to the
and high shear rate (CR, VSEP) membrane
precipitation of lignin (and partly extractives)
filtration modules were tested. 10 wt-% kraft
on the membrane surface, which rapidly led to
black liquor (UPM Kaukas mill) was successfully
permanent losses in ion exchange efficiency of
concentrated to about 90% volume reduction
the membrane. In a typical case, the efficiency
with both low and high shear rate modules
for the first 4 hours was 0.25 kWh/mol and
using NP010 (1 kDa) membrane. The flux of the
during 4-9 hours 0.42 kWh/mol.
CR-filter was significantly higher than that of
the VSEP-filter or the DSS-filter. In the CR-filter,
Electrodialysis was also tested as an alternative
the average flux was over 130 kg/(m2h) up to
for ion exchange in liberation of the acids.
a volume reduction of 80%. When the volume
A fraction of hydroxy acids obtained by
reduction exceeded 75% the flux started to
ultrafiltration and chromatography was used as
decrease very rapidly from 100 kg/(m2h) to 5 kg/
the feed. The fraction used as feed contained
(m2h) at a volume reduction of 90%. It was thus
approximately 3.3 g/L of lignin.
concluded that the CR-filters with a rotating
blade near the membrane surface were the
In the first phase, the fraction was processed
best choice for ultrafiltration of black liquor.
by ED. After this experiment the membranes
Table 2. Concentrations of lignin and carboxylic acids in the concentrated product fractions recovered and
purified from hardwood (HW) and softwood (SW) soda black liquors.
Fraction
Mass
Lignin,
XISA,
GISA,
2,5-
2-OH-
Lactic
Glycolic
Oxalic
Acetic
Formic
reducti-
g/L
g/L
g/L
DHPA,
butanoic
acid,
acid,
acid,
acid,
acid,
g/L
acid,
g/L
g/L
g/L
g/L
g/L
on,
wt-%
g/L
HW black
liquor
3
85
1.21
6.2
7.4
0.00
0.00
0.4
1.0
3.0
2.5
0.0
4
89
1.41
46.2
22.9
0.00
10.2
7.9
9.7
1.5
23.3
3.9
5
85
2.13
5.0
2.2
0.00
16.3
4.9
3.5
0.0
20.9
10.6
6
92
1.92
0.00
0.00
0.00
4.1
0.6
0.3
0.5
2.8
2.8
92
1.03
5.2
45.8
0.00
0.00
1.7
2.9
3.8
3.6
0.7
SW black
liquor
1
80
2
96
4
53.4
148
4.38
7.9
34.1
24.0
0.0
13.0
9.2
3
89
2.49
8.4
2.0
2.20
5.6
8.5
5.0
0.0
7.0
15.2
were kept in the initial fraction and, after two
of pH on the retention of acid compounds was
weeks, the same membranes were used again
investigated by increasing the pH of the feed
for ED. The same procedure was repeated
liquor stepwise from pH 2.3 to 12 with NaOH.
after six weeks. As can be seen from Table 3,
efficiency clearly dropped already after 2 weeks
It was found that pH had a marked effect
from 0.23 kWh/mol to 0.29 kWh/mol. After six
on permeate flux and retention, and thus
weeks, the efficiency was 0.28 kWh/mol. This
on hydroxy acid separation. Higher pH can
efficiency deterioration was probably due to
either increase retention, as with sulphate and
the conditions used in the durability tests, i.e.,
xyloisosaccharinic acid XISA, or decrease it, as
when bipolar membranes were soaked in the
with formic acid (Figure 5). Nanofiltration can
hydroxy acid fraction also its anionic side was
thus be used to fractionate organic acids into
influenced, which would not be the case under
two fractions that are rich in different hydroxy
normal operating conditions.
(or volatile) acids. Acetic and formic acids
permeated the NF membrane especially at high
Membranes were visually estimated after 2 and
pH, and isosaccharinic acids and sulphate ions
6 weeks of soaking and no visual changes were
were concentrated in the retentate stream.
observed. After ED runs a thin layer of lignin
Nanofiltration at pH 2.3 led to a concentrated
was precipitated on the surface of the bipolar
stream with an acids content of about 80% of
membrane’s cationic side. This layer could be
total organic matter. Furthermore, GISA purity
rinsed off with water. The results indicate that
in the concentrate was almost 40% based on
at least 90% of initial lignin is removable from
total organic matter.
the black liquor by ED treatment.
Fractionation
of
hydroxy
acids
by
4.2 Polymeric materials from fractionated
black liquor
nanofiltration. The use of nanofiltration to
separate carboxylic acids from each other was
Fractionated black liquor samples for the
demonstrated using Desal-5 DK membranes.
polymerization
A kraft black liquor that was pre-treated by
partners in the project. One fraction (HW1) from
cooling crystallization and acid precipitation to
hardwood black liquor and three fractions (SW1,
remove lignin was used as the feed. The effect
SW2, and SW3) from softwood black liquor
were
obtained
from
the
Table 3. Results obtained from the Lappeenranta fraction (as such and after the ED experiments with
varying treatment time).
Parameter
Fresh
2 weeks
6 weeks
Hydroxy acids (g/L)
19.6
20.1
20.1
Efficiency after 1 h
0.23
0.29
0.28
2.37
2.23
2.07
Lignin (at 280 nm; alkali so- 0.36
0.26
0.24
1.09
1.11
0.19
0.01
(kWh/mol)
pH after ED
luble) (g/L)
Lignin (at 205 nm; acid so- 1.36
luble) (g/L)
Residual sodium (g/L)
0.30
81
Figure 5. Effect of pH on the retention of various organic acids during nanofiltration with Desal-5 DK
membrane (70 °C, 25 bar).
were used. The fractions were purified by the
a catalyst. Temperature of the reaction was
abovementioned combination of ultrafiltration
increased gradually from 130 °C to 160 °C while
and
Two
maintaining a pressure of 500 mbar. Pressure
samples of black liquor were purified by
was then gradually decreased to 30 mbar. Once
electrodialysis (ED). The black liquors originated
the target pressure was achieved, the reaction
from soda-AQ pulping. The compositions of the
was allowed to continue for 24 h. Polymeric
various fractions were calculated from results
materials were successfully obtained from all of
obtained by capillary electrophoresis (Table 4).
the fractions by condensation polymerization.
size-exclusion
chromatography.
The distillate obtained from the dilute hydroxy
The dilute aqueous fractions of black liquor were
acid mixtures was analysed to determine how
polymerized by condensation polymerization.
the polymerization proceeds. The distillates
A predetermined reaction volume was placed
analysed were shown to contain in all cases
into a suitable round-bottomed flask equipped
formic and acetic acid. Glycolic, lactic and
with a Teflon® covered magnetic stirring bar
2-hydroxybutyric acids were also detected in
and a distillation head. Sn(Oct)2 (0.1 wt-%
some cases.
based on analysed acid content) was used as
Table 4. Compositions [g/L] and molar ratios (χ) of black liquor fractions analysed by capillary
electrophoresis.
82
OA
FA
AA
GA
LA
2HBA
2,5-DHPA
XISA
g/L
g/L
g/L
g/L
g/L
g/L
g/L
g/L
g/L
(χOA)
(χFA)
(χAA)
(χGA)
(χLA)
(χ2HBA)
(χDHPA)
(χXISA)
(χGISA)
HW1
1.5 (1.0)
3.9 (5.2)
23.3 (23.9)
9.7 (7.8)
7.9 (5.4)
10.2 (6.1)
SW1
3.8 (2.8)
0.7 (1.0)
3.6 (4.0)
2.9 (2.5)
1.7 (1.2)
GISA
46.2 (18.9)
22.9 (8.5)
5.2 (2.3)
45.8 (18.4)
148.1 (27.8)
SW2
9.2 (6.2)
13.0 (6.8)
24.0 (9.8)
34.1 (11.8)
7.9 (2.4)
4.4 (1.0)
53.4 (11.1)
SW3
15.2 (27.7)
7.0 (9.8)
5.0 (5.5)
8.5 (7.9)
5.6 (4.5)
2.20 (1.4)
8.4 (4.7)
2.0 (1.0)
SODAAQ1
0.4 (3.2)
0.9 (6.1)
0.3 (1.8)
0.5 (2.2)
0.2 (1.0)
1.2 (3.5)
3.0 (6.7)
SODAAQ2
2.0 (14.8)
1.9 (10.5)
0.9 (4.1)
1.1 (4.3)
0.6 (1.8)
1.6 (1.0)
5.0 (10.1)
0.4 (1.0)
All products had the physical appearance of
Glycolide production and ring-opening
solid materials or highly viscous fluids. This is
polymerization of glycolide
taken as primary evidence for the formation
In addition, a method for glycolide production
of polymers. Similarly, the thermal properties
by polycondensation of glycolic acid using
of the samples suggest that polymers were
a catalyst under reduced pressure suitable
obtained. The Tgs varied between -1 and 49
for large-scale production was successfully
°C, depending on the sample. The reason for
developed. The production of glycolide using
this variance is not understood and further
the chosen distillation method produced a yield
experiments should be done with larger
of only 20% glycolide from the polycondensate
amounts of polymer formed. The properties
of glycolic acid. Using a catalyst, glycolide
of
reaction
formation reached 100 g/kg polycondensate/
volumes, yields, theoretical yields calculated,
hour. However, the simultaneous formation
thermal properties and molecular weights are
of insoluble residue was a main concern for
presented in Table 5.
the development of an industrial continuous
the
characterized
products,
production process based on the studied
The obtained polymer yields were generally
method. The purity of the produced glycolide was
higher than the calculated yield based on
comparable to commercial polymerization grade
the amount of acids. This indicates that the
glycolide. Collecting the distillate of glycolide in a
condensation is incomplete and there is still
nonpolar solvent and re-crystallization yields a
unreacted
result
purity of 99%, which is suitable for production of
was expected as the OH/COOH ratios are not
high molecular weight polymers. Polymerization
even. The polymers obtained were found to
of high molecular weight polyglycolic acid
be relatively poorly soluble in most common
(PGA) was demonstrated using ring-opening
organic solvents. The polymers were insoluble in
polymerization in the melt (0.1 wt-% SnOct,
chlorinated solvents, hydrocarbons and alcohols.
250°C, 4h). The glycolide samples along with
The solubilities varied from poor to good when
a commercial reference were polymerized
dissolved into polar aprotic solvents such as
successfully (Table 6). The polymers obtained
DMSO and THF. The solubility of the materials
showed some differences in structural analysis
depended on the material composition, although
(Figure 6). The additional peaks seen with the
thorough analysis of this was not possible due to
polymers prepared from glycolide samples 53
the limited amounts of material available.
and 102 are due to the polymer end groups. The
material
remaining.
This
minor peaks observed at ~69 ppm and ~66 ppm
are due to residual glycolide.
Table 5. Reaction volumes, obtained and theoretical yields, obtained and theoretical glass transition
temperatures and obtained molecular weights of the polymers obtained from black liquor fractions.
Volume
Acid
Yield
Yield
Tg
Tg,calc.
Mn,theor
Mn
Mw
[mL]
content
[g]
[%]
[°C]
[°C]
[g/mol]
[g/mol]
[g/mol]
[g/L]
HW1
10
125.5
1
96
-1
11
770
734
1010
SW1
20
63.6
1.38
128
27
6
1740
1030
1420
SW2
2
294.0
0.56
112
6
8
620
540
750
SW3
20
53.8
0.82
88
49
57
3560
1600
2400
SODAAQ1
200
6.5
1.27
117
42
8
670
1330
1900
SODAAQ2
200
13.6
1.72
78
32
9
1010
1030
1410
83
Table 6. Results from glycolide polymerizations.
Glycolide
PURAC
Yield
99%
GPC
Tg
Mw/Mn
(°C)
(°C)
5,890 / 3,400
38
217
Tm
Hycail 1
98%
25,700 / 13,400
43
210, 221
Hycail 53
99%
22,100 / 11,500
44
209, 222
Hycail 102
99%
36,600 / 17,400
44
221
4.3 Glycolic acid by fermentation
cycle and directs the metabolic flux towards
the cycle, thus allowing the yeast to produce
acid
glycolic acid (Figure 7). Development of
was demonstrated using host organisms
bioreactor cultures and the selection of a
Saccharomyces cerevisiae, Aspergillus niger,
suitable yeast host led to improved production
and Kluyveromyces lactis. Glycolic acid was
levels that demonstrate technical feasibility.
produced in the glyoxylate cycle of the cell.
Production of glycolic acid was shown to be
Expression of the glyoxylate reductase gene
possible also at low pH, which is an advantage
and deletion of the malate synthase gene are
for the purification process and a clear benefit
the minimum requirements for glycolic acid
when compared to Escherichia coli, which has
production.
also been reported to be used as a host for
Biotechnical
production
of
glycolic
glycolic acid production. At low pH there is
Yeast codon optimized glyoxylate reductase
less need for neutralization and the separation
gene, GLYR1, from the plant Arabidopsis
process is thus easier because less gypsum is
thaliana was introduced to the production
formed and the glycolic acid is in acid form.
host. Overexpression of this gene combined
Low pH also decreases the risk of bioreactor
with other modifications boosts the glyoxylate
contamination.
Figure 6. 13C NMR comparison showing only minute differences in polymer structures.
84
Figure 7. Modified glyoxylate
cycle in S. cerevisiae.
Overexpressed genes are
presented in green, deleted
genes in red.
The best result (17.2 g/l) in the production of
After five days, about 3 g l-1 of glycolic acid was
glycolic acid was achieved by fermentation
produced in flask cultivations. The modified
of
strain
the
engineered
Kluyveromyces
lactis
strain. The benefit of K. lactis compared to
was
grown
on
unbuffered
media
containing 20 g l-1 xylose and 20 g l-1 ethanol
S. cerevisiae is that it is a Crabtree negative
and fed daily with additional 10 g l-1 ethanol.
yeast which favours respiratory metabolism,
Further work is needed to increase the
meaning that the organism does not catabolize
production rate and also to bypass the ethanol
sugars to ethanol as efficiently as S. cerevisiae.
step, as it has been shown that only ethanol
is converted to glycolic acid, whereas xylose
The first step in constructing the glycolic acid
and other sugar substrates are either used
production strain in K. lactis was to delete
solely for cell growth or are first converted to
malate synthase in order to prevent the
ethanol before converting to glycolic acid. The
conversion of glyoxylate to malate. In addition,
result shows that K. lactis is a promising host
the cytosolic isocitrate dehydrogenase was
for glycolic acid production as it is producing
deleted and, finally, the S. cerevisiae codon-
more glycolic acid with fewer modifications
optimized glyoxylate reductase, GLYR1, was
than S. cerevisiae strains.
overexpressed from a multicopy plasmid.
85
Kluyveromyces lactis bioreactor cultivations
K. lactis strain H3986 was grown in a Biostat
results
CT-DCU bioreactor at pH 5.0, at 30°C, 1 volume
air [volume culture]-1 min-1 (vvm) and 500 rpm
The work focuses on separation of hydroxy acids
agitation. Xylose (20 g l-1) and ethanol (20 g l-1)
from black liquor and their further upgrading,
were provided as carbon source at the beginning
e.g. as hot melts or reactive monomers. From
of the fermentation. Xylose and ethanol were
the industry point of view, if the separation
fed to the bioreactor as separate feeds based
concept proves economically feasible, hydroxy
on their consumption. The fermentation was
acid based products recovered from black
monitored for 12 days (Figure 8).
liquor would offer opportunities for pulp
and papermaking companies to utilize this
Extracellular metabolites in cell-free spent
side-stream as a valuable raw material for
culture medium were analysed by capillary
environmentally friendly products.
electrophoresis. H3986 produced extracellularly
17.2 g glycolic acid l-1 after 9 days at pH 5.0 (Table
7). The yield of glycolic acid on xylose-ethanol
media was approximately 0.13 g glycolic acid [g
ethanol + xylose]-1. Acetate was also produced
towards the end of fermentation, but as the
Table 7. Glycolic acid production by strain H3986 at
pH 5.0 in a bioreactor.
glycolic acid level was already close to maximum
at this stage, it would have been possible to stop
the fermentation before acetate accumulation,
thus facilitating the separation process.
Glycolic acid production (g l-1)
Day 0 Day 2 Day 4 Day 6 Day 8 Day 9
0
9.9
13.8
14.8
16.1
17.2
Figure 8. Xylose, ethanol and oxygen consumption and glycolic acid, acetate and CO2 production.
86
6. Networking
The research was carried out jointly by research organisations and Finnish bioeconomy cluster
companies. Table 8 below presents the research partners and their roles.
Hycail
Preparation of glycolide from glycolic acid
Kemira
Industrial tutor
Fractionation and purification of hydroxyl acids from black liquor by
Technology
membrane filtration and chromatographic separation
Metsä Fibre
Industrial tutor
Expertise in oxidation of sugars to hydroxy acids
Developing the separation of hydroxy acids from black liquor by
electrodialysis
UPM-Kymmene
VTT
WP leader. Development of a chromatographic separation method
for hydroxy acids from black liquor and analysis. Polymerization and
copolymerization of hydroxy acids. Development of an enzymatic route to
glycolic acid from sugars.
Hellstén, S. Recovery of biomass-derived val-
Koivistoinen, O.M., Kuivanen, J., Barth D., Turk-
uable compounds using chromatographic and
ia H., Pitkänen, J-P., Penttilä, M. and Richard,
membrane separations, Doctoral dissertation,
P. Glycolic acid production in the engineered
Lappeenranta University of Technology, 2013.
yeasts Saccharomyces cerevisiae and Kluyveromyces lactis, Microb Cell Fact 12, 2013, 16 pp.
Hellstén, S., Heinonen, J. and Sainio, T. Size-exclusion chromatographic separation of hydroxy
Koivistoinen, O., Kuivanen, J., Penttilä, M. and
acids and sodium hydroxide in spent pulping
Richard, P. Eukaryotic cell and method for pro-
liquor, Sep. Purif. Technol., 118, 2013, 234–241.
ducing glycolic acid, WO13050659A1.
Hellstén, S., Lahti, J., Heinonen, J., Kallioinen,
Pirttimaa, M., Rovio, S., Harlin, A., Ropponen,
M., Mänttäri, M. and Sainio, T. Purification pro-
J. and Gädda, T. Polymers derived from isolat-
cess for recovering hydroxy acids from soda
ed hydroxy acids obtained from hardwood and
black liquor, Chem. Eng. Res. Des., 91, 2013,
softwood black liquor, submitted.
2765-2774.
Koivistoinen, O. Catabolism of biomass-derived sugars in fungi and metabolic engineering
as a tool for organic acid production, Doctoral
dissertation, University of Helsinki, 2013.
87
BIOLOGICAL EFFECTS OF
WOOD-BASED EXTRACTS
AND COMPOUNDS
IN MODELS OF HUMAN
DISEASE
CONTACT PERSON - Work Package 5 leader Niina Saarinen-Aaltonen, [email protected]
Stora Enso: Jukka Kahelin
University of Helsinki: Raisa Haavikko, Vânia Moreira, Jari Yli-Kauhaluoma
University of Tampere: Heikki Eräsalo, Mirka Laavola, Tiina Leppänen, Eeva Moilanen
University of Turku: Sari Mäkelä,Lauri Polari, Niina Saarinen-Aaltonen, Emrah Yatkin
UPM-Kymmene: Mika Hyrylä, Suvi Pietarinen
VTT Technical Research Centre of Finland: Kirsi Bromann, Tiina Nakari-Setälä, Mervi Toivari
Åbo Akademi University: Annika Smeds, Stefan Willför
88
ABSTRACT
The project aimed at building a Finnish knowledge platform on the health-promoting
potential of wood-derived compounds. The focus was on obesity-associated disorders,
inflammatory diseases – especially (osteo)arthritis and allergy, and cancer, i.e. diseases
that are common and increasingly prevalent in Finland and other Western countries.
The work demonstrated through various cell-based assays in vitro and in animal
models in vivo that pine knot extract and its components have anticarcinogenic and
immunomodulatory / anti-inflammatory properties and alleviate obesity-associated
disorders. Mechanisms of action relevant to several diseases in the focus areas were
identified, along with signalling mechanisms relevant to specific diseases.
The results contribute greatly to our general understanding of the effects of wood-derived
compounds on human health. A unique, interdisciplinary research environment was created,
providing an innovative knowledge platform enabling identification of novel applications
for wood-derived compounds. The focus of the research on bioactive compounds derived
from raw material sources available for large-scale production is also unique and increases
Finnish competence for further exploitation of innovations in this field. The work paves the
way for the development of high-value products from unexploited raw material sources as
an integral part of the Finnish forest industry renewal process.
Keywords:
pine knot extract, stilbenoids, obesity, adipose tissue, aromatase, breast cancer,
prostate cancer, inflammation, arthritis, cartilage, allergy
89
1. Background
2. Objectives
Nature is a rich source of bioactive compounds
The project was designed to contribute to
with therapeutic potential. It is estimated that
building a globally competitive and unique
about half of all drugs used in current medical
Finnish knowledge platform on wood-derived
treatment originate from plants and other
compounds and their potential use as health-
natural sources. Nordic wood, especially conifer
promoting agents.
knotwood, is a rich source of compounds with
health-promoting potential, such as polyphenols.
The main objective was to identify and
Some of these compounds are similar to those
biologically
found in other sources, such as edible plants.
wood knot and bark components with the
However, unlike in many other plants, the majority
aim of providing preclinical proof-of-concept
of polyphenolic compounds in wood are present
level evidence in at least one of the focus
in unconjugated form. In addition, polyphenol-
areas: obesity-associated health problems,
rich knot material is available in large quantities
cancer,
as a side product of current industrial processes.
relation to (osteo)arthritis and allergy. Each
Therefore, isolation of polyphenols from knot-
line of research began by recognizing relevant
enriched wood material in high quantities for
target(s) and continued by identifying effective
further exploitation is feasible.
extract(s) and/or compound(s) and further
characterize
and
health-promoting
inflammation,
especially
in
documenting the efficacy and preliminary
In this project, wood materials that are not
safety of the selected materials in cell-based
important for pulp production were investigated.
assays and/or animal experiments (in vivo
The research focused on health problems that
disease models) in comparison with previously
are common and continuously increasing in
known control compounds.
Finnish and other Western populations: obesity,
inflammatory diseases, especially osteoarthritis
and allergy, and cancer. Obesity is a risk factor
for
development
of
metabolic
syndrome,
which is associated with type 2 diabetes and
Initially, the project involved three main raw
cardiovascular disease. In Finland, 60% of men
materials: pine knot extract, spruce knot extract,
and 50% of women are overweight or obese and
and birch bark extract, and purified compounds
15% of men and 5% of women have metabolic
of these, respectively. Based on the findings
syndrome. It has been estimated that half a
during the project, the work was further focused
million Finns have symptomatic osteoarthritis
on pine knot extract and its compounds.
and about 30% of Finns suffer from various
forms of allergic diseases. In addition, the
3.1 Obesity-associated health problems
incidence of certain cancers, in particular
90
prostate cancer and breast cancer, is increasing
The work was focused on obesity-induced
in Western countries. By 2020, prostate cancer
endocrine disturbances caused by dysregulation
will constitute almost 50% of diagnosed cancer
of aromatase (CYP19A1) gene expression in white
cases in men. Breast cancer is now, and will
adipose tissue. Aromatase enzyme catalyzes
continue to be, responsible for more than 40%
the final step in oestrogen biosynthesis, i.e.
of cancer cases in women. Clearly, there is an
conversion
urgent need for novel preventive means and
and
treatment options against these diseases.
and oestradiol). White adipose tissue is an
of
androgens
testosterone)
to
(androstenedione
estrogens
(oestrone
important site for extragonadal aromatization 3.3 Immunomodulatory / antiand oestrogen production in man. To investigate inflammatory properties of pine knot
pine knot extract effects in vivo, a humanized extract and its compounds
transgenic hAro-Luc reporter mouse was utilized.
These mice express the full-length promoter To screen the anti-inflammatory potential of the
region of the human aromatase gene, and can pine knot extract and its known constituents,
be used to study, for example, obesity-related a widely used animal model in pharmacology
factors that regulate aromatase expression in research,
i.e.
carrageenan-induced
paw
vivo. Obesity was induced by high-fat diet (HFD). inflammation, was used. The advantage of
Effect of pine knot extract on weight gain and this model is that the effects can be compared
body composition (adiposity) was determined to large background data on the activity of
and serum biomarkers of metabolic disturbance various anti-inflammatory compounds and
were measured. Obesity-induced adipose tissue series of other natural products. Also, the
inflammation was assessed using histological early inclusion of in vivo disease models in
parameters in the tissue and by measuring the evaluation of the biological activity of
adipose tissue proinflammatory cytokine levels. the extract and compounds of interest also
Adipose tissue cultures and bone marrow stromal gave a preliminary understanding of the
cell cultures were established as novel tools bioavailability of the investigated materials.
to investigate factors that regulate aromatase Furthermore, additional in vivo disease models
expression in fat tissue.
were developed.
3.2 Effects on prostate cancer
Cell-based
assays
were
established
to
investigate the effects of the extract and
Anticarcinogenic
potential,
mechanism
of its
constituents
on
inflammatory
gene
action, and effective concentration range of expression in various inflammatory cells and
pine knot extract and its main polyphenols in chondrocytes. The cell culture conditions
and their metabolites were evaluated in in were adjusted to mimic the inflammatory
vitro assays by using human prostate and milieu in vivo and the cells were stimulated
breast cancer cells and in vivo by using accordingly. In addition to appropriate cell
human cancer cell derived tumours in mice. lines, also primary human cell cultures were
in vitro, the effects of pine knot extract and used
when
possible.
Inflammatory
gene
compounds derived therefrom were tested expression was measured using standard
for proliferation and apoptosis in androgen- procedures, e.g. quantitative real-time reverse
independent human prostate cancer cells.
transcriptase polymerase chain reaction (RTqPCR) to detect mRNA levels, and Western
The effective dose of pine knot extract in vivo blotting and enzyme-linked immunosorbent
was assessed in prostate cancer tumours grown assay (ELISA) to measure protein levels.
in mice. Growth of the tumours was followed Also, an array-based approach was used
and several biomarkers of tumour development where appropriate. Furthermore, the effects
and mechanisms of chemoprevention were on intracellular signalling mechanisms were
assessed using morphological and biochemical investigated using, inter alia, phosphoprotein
analyses. Statistical multivariate analyses were and reporter gene assays.
applied to combine essential tumour growth
markers and to identify effective dosing of pine
knot extract.
91
4. Results
Obesity
induces
chronic
low-grade
inflammation in adipose tissue, which causes
4.1 Pine knot extract attenuates obesityinduced metabolic disturbances and
aromatase expression in adipose tissue
numerous functional changes that promote
the
development
of
obesity-associated
diseases. Formation of crown-like structures
(CLS), i.e. necrotic adipocytes surrounded by
A mouse model of diet-induced obesity
macrophages, and increased levels of tissue
allowed us to study simultaneously multiple
proinflammatory cytokines are typical for
aspects of obesity-associated disorders in
obesity-related adipose tissue inflammation
vivo. The effects of two dietary doses of a pine
and dysfunction. The higher dose of dietary
knot extract were investigated: “low dose”
pine knot extract decreased the number of CLS
and “high dose”, which resulted in 32.5 mg/
in visceral and subcutaneous white adipose
kg and 162.5 mg/kg body weight exposures,
tissues (Figure 1) and reduced the tissue level of
respectively. The “low dose” corresponds
proinflammatory cytokines. In summary, these
roughly to 1g daily intake of phenolics in a 70
data indicate that dietary pine knot extract
kg human, i.e. an intake achievable through
can attenuate obesity-induced adipose tissue
diet, while the “high dose” corresponds
inflammation in vivo.
roughly to a 2g daily intake of pinosylvins in
a 70 kg human. As expected, high-fat diet
Functional changes induced by obesity include
(HFD) increased body weight and body fat
induction of aromatase expression in adipose
content in male mice compared to low-fat
tissue, which, in turn is one of the key events
diet (LFD). Administration of pine knot extract
leading
for 8 weeks in HFD diet was well tolerated.
disturbances.
Neither dose of pine knot extract significantly
necessary for the production of oestrogen
affected body weight gain or fat content.
from androgens. Downregulation of oestrogen
However, a higher dose of pine knot extract
biosynthesis in adipose tissue has an impact, for
administered in the HFD diet decreased
example, on the prevention of obesity-related
serum leptin, resistin, insulin, and fasting
hypoandrogenemia in obese men and on the
blood glucose levels, which are hallmarks of
development of oestrogen-responsive breast
metabolic disturbances in humans.
cancer in postmenopausal obese women.
to
obesity-associated
Aromatase
is
an
endocrine
enzyme
Figure 1. Density of crown-like structures (CLS) in visceral (A) and subcutaneous fat (B). LFD, low-fat diet;
HFD, high-fat diet, HFD-PKE pine knot extract containing high-fat diet.
92
In humans, expression of aromatase is highly
aromatase gene reporter expression was
regulated through untranslated first exons that
modulated by pine knot extract in MSCs. In
are differently utilized in different tissues. In
addition, other more indirect effects of pine
rodents, the regulatory region of the aromatase
knot extract seen in the in vivo setting may, at
gene is much less complex and, unlike in
least in part, account for the downregulation
humans, the expression level in adipose tissue
of Luc expression in subcutaneous fat. In
is very low. Therefore, we used a humanized
summary, these data suggest that pine knot
transgenic hARO-Luc reporter mouse. These
extract affects oestrogen biosynthesis in male
mice express the full-length regulatory region
adipose tissue by modulating aromatase gene
of the human aromatase gene attached to a
expression and may thus have potential to
luciferase (Luc) reporter gene.
attenuate excessive oestrogen production in
white adipose tissue of obese men.
In hAro-Luc mice, we showed that HFDinduced
adiposity
was
associated
with
upregulation of Luc expression in adipose
tissue. In line with this, adipose tissue Luc
4.2 Pine knot extract shows
anticarcinogenic efficacy in prostate
cancer
activity correlated positively with adipose
tissue
levels.
In this project, we showed that pine knot extract
Importantly, we demonstrated that dietary
pro-inflammatory
cytokine
and its stilbenoids (monomethyl pinosylvin
pine extract down-regulates the expression of
and pinosylvin), and lignans (matairesinol and
human aromatase gene in subcutaneous fat of
nortrachelogenin) have antiproliferative and
obese HFD-fed male mice (Figure 2).
proapoptotic efficacy at ≥40 μM concentration
in vitro (Figures 3 and 4). We also showed that
In
human
adipose
is
pine extract (≥ 10 mg/L) and its stilbenoids
mainly expressed in mesenchymal stromal
enhance TRAIL-induced apoptosis already at
cells
(MSCs).
≥10 μM concentration in vitro (Figure 4B).
MSC
cells
We
from
tissue,
isolated
hARO-Luc
aromatase
and
cultured
mouse
bone
marrow. As expected, Luc expression in
Four
MSCs
B1,
was
stimulated
by
glucocorticoids
main
compounds
pinosylvin,
of
pine
monomethyl
extract
pinosylvin,
and proinflammatory cytokines through the
matairesinol,
aromatase gene promoter I.4. Interestingly,
identified to account for the observed pine
and
nortrachelogenin,
were
knot extract effects. These compounds, when
combined in the same ratio as present in the
extract, resulted in similar responses in the
cell proliferation and apoptosis assays as the
extract and, when tested as single compounds,
were effective at ≥ 10μM concentrations
(Figures 3C and 4). These data indicate that
concentrations of ≥ 10 mg/L of pine extract
or ≥ 40μM single pine extract compounds
are required for inhibition of proliferation and
induction of apoptosis in human prostate
Figure 2. Aromatase reporter expression in male
subcutaneous white adipose tissue. LFD, lowfat diet; HFD, high-fat diet; HFD-PKE pine knot
extract containing high-fat diet.
cancer cells in vitro.
93
Figure 3. Pine knot extract and its polyphenols inhibit proliferation of PC-3M-luc2 human prostate
cancer cells. PKE, pine knot extract; LS, lignan-stilbenoid mixture containing pinosylvin (PS),
monomethyl pinosylvin (MEPS), matairesinol (MR), and nortrachelogenin (NTG). Ab, abietic acid; RV,
resveratrol. Figure published in PlosOne 2014, 9(4):e93764.
Figure 4. Pine knot extract and its compounds induce apoptosis in PC-3M-luc2 human prostate cancer
cells (A) and sensitize these cells to TRAIL-induced apoptosis (B). PKE, pine knot extract; LS, lignanstilbenoid mixture containing pinosylvin (PS), monomethyl pinosylvin (MEPS), matairesinol (MR), and
nortrachelogenin (NTG). Ab, abietic acid; RV, resveratrol. Figure published in PlosOne 2014, 9(4):e93764.
Two in vivo studies investigating the effects
(i.e. tumour volume, vascularization, and cell
of pine knot extract on advanced androgen-
proliferation) (Figure 5).
independent prostate cancer in vivo were
completed. Two doses of the extract were
Urine and serum analyses of “high dose” pine knot
investigated: “low dose” resulting in 32 mg/kg/
extract fed mice revealed significant absorption
body weight exposure and “high dose” resulting
and metabolism of the extract compounds.
in 162.5 mg/kg/body weight exposure. Three-
In serum, high micromolar concentrations of
week peroral exposure to high-dose pine knot
nortrachelogenin, and monomethyl pinosylvin
extract B1 (52 mg of lignans and stilbenoids
along with resveratrol were measured. Resin
per kg body weight) showed anti-tumorigenic
acids that are present in the pine knot extract
efficacy, demonstrated by multivariate analysis
were not detected in urine or serum samples.
combining essential markers of tumour growth
94
Figure 5. Relation between tumour vascularization, tumour cell proliferation and tumour volume. The
hyperplane indicates that two of the groups (vehicle in black and high dose in green) were linearly
separable when the three factors were considered together. Figure published in PlosOne 9(4): e93764.
In summary, these data demonstrate that
if aberrantly activated or regulated, prolonged
orally-administered pine knot extract is well
or inappropriately focused (e.g. against host
tolerated and inhibits the growth of prostate
tissues, as in autoimmune diseases, or against
cancer tumours. The in vitro results indicate
normally harmless allergens, as in allergic
that pine knot extract derived lignans and
diseases) the inflammatory response has
stilbenoids and their metabolites account
considerable potential to cause harm and
for the anticarcinogenic effect. The main
may lead to the development of inflammatory
polyphenol in pine knot extract, monomethyl
diseases, such as allergy, asthma or arthritis.
pinosylvin,
Despite recent successes in the development
was
identified
as
a
novel
bioavailable stilbenoid with anticarcinogenic
of
potential against prostate cancer. In addition,
drugs, there are still considerable unmet needs
especially
biological
ingestion of pine knot extract increased
in the treatment of inflammatory diseases. In
serum resveratrol concentrations markedly,
fact, for most inflammatory diseases, current
indicating that the extract is a novel and cost-
drugs can only offer symptoms relief and no
effective source of resveratrol, monomethyl
curative or disease-modifying treatments are
pinosylvin and other potentially beneficial
available. In the present research programme,
lignans and stilbenoids.
we
investigated
the
anti-inflammatory
anti-inflammatory
/
immunomodulatory properties of pine knot
4.3 Pine knot extract and its stilbenoid
constituents have anti-inflammatory
properties in vivo
extract and its constituents, especially in
relation to disease mechanisms of (osteo)
arthritis and allergic inflammation. Examples
of the results are presented below.
Inflammation is a protective response in the
human body that aims to eliminate microbes
To determine whether pine knot extract
and other offending agents as well as cancer
has
cells and injured or necrotic tissue. However,
we utilized a widely-used animal model in
anti-inflammatory
potential
in
vivo,
95
pharmacology research, i.e. carrageenaninduced paw inflammation, in the mouse.
Interestingly, the standard pine knot extract
when given as a single oral dose of 100 mg/kg
4.4. Pine knot extract and its
stilbenoid constituents down-regulate
inflammatory gene expression in
inflammatory cells and in chondrocytes
significantly attenuated carrageenan-induced
inflammation, as shown in Figure 6A.
In order to understand the anti-inflammatory
properties of the pine knot extract and its
Following this finding, we investigated whether
stilbenoid constituents at the cellular level and
the stilbenoid constituents of the extract
their effects on the mediators of inflammation,
might be responsible for the anti-inflammatory
we investigated their effects on various cells
bioactivity discovered in the pine knot extract.
participating in different types of inflammation.
The extract is known to contain two principal
Selected effects of the pine knot extract and
stilbenoids, i.e. pinosylvin and monomethyl
its stilbenoids pinosylvin and monomethyl
pinosylvin. These compounds had a clear
pinosylvin on macrophages and chondrocytes in
anti-inflammatory effect in the carrageenan-
cell culture conditions mimicking inflammatory
induced paw inflammation model in the mouse,
milieu are presented below.
as can be seen in Figure 6B. Furthermore,
they were more potent than resveratrol, an
Macrophages
earlier known natural stilbenoid, which was
Macrophages are key inflammatory cells
used as a control compound. The efficacy of
that are differentiated in tissues from blood
the two pine stilbenoids was comparable to
monocytes.
that of the standard anti-inflammatory drug
functions in the first line of defence against
dexamethasone, although the pine stilbenoids
microbes and in the development of specific
were needed in higher doses to obtain the
lymphocyte-mediated immune response as
efficacy
well as in the regulation of inflammatory and
of
the
dexamethasone.
anti-inflammatory
steroid
Macrophages
have
various
repair mechanisms through the production of
a variety of inflammatory mediators.
Figure 6. Anti-inflammatory properties of pine knot extract and its stilbenoid constituents pinosylvin
and monomethyl pinosylvin in carrageenan-induced paw inflammation in the mouse. In (A) the pine
knot extract (100mg/kg) was dosed orally and in (B) pinosylvin (100 mg/kg) and monomethyl pinosylvin
(100 mg/kg) as well as control compounds resveratrol (100 mg/kg) and dexamethasone (2 mg/kg)
were given intraperitoneally 2h prior to the inflammation was induced by injecting carrageenan into
the paw. Results are expressed as mean ± SEM, n=6.
96
In the present study, we investigated the effects
manner. Interestingly, expression of these
of pine knot extract and its stilbenoids on
inflammatory
inflammatory gene expression in macrophages
by pinosylvin and monomethyl pinosylvin
activated through the TLR4 pathway by
(stilbenoids present in the extract) as well as
adding bacterial endotoxin lipopolysaccharide
by resveratrol, which was used as a control
(LPS) into the culture. As seen in Table 1 below,
stilbenoid.
genes
was
also
inhibited
pine knot extract inhibited the production
of inflammatory factors interleukin 6 (IL-6),
Chondrocytes
monocyte chemotactic protein 1 (MCP-1) and
Osteoarthritis (OA) is the most common
inducible nitric oxide synthase (iNOS) and its
joint disease worldwide. The disease affects
product nitric oxide (NO) in a dose-dependent
the entire joint causing disability and pain.
Table 1. The effects of pine knot extract and its components pinosylvin and monomethyl pinosylvin
as well as the control stilbenoid resveratrol on nitric oxide (NO), interleukin 6 (IL-6) and monocyte
chemotactic protein 1 (MCP-1) production and inducible nitric oxide synthase (iNOS) expression in
activated macrophages. The results are expressed as mean ± SEM; * indicates p<0.05 and ** = p<0.01.
97
The primary cause of OA remains unknown.
pine knot extract inhibited the production
Degradation of the cartilage matrix is the
of the three MMP enzymes typical of OA
most important feature of OA pathology. The
pathogenesis (i.e. MMP-1, MMP-3 and MMP-
degradation is caused by an imbalance between
13) in a dose-dependent manner. The effect
catabolic and anabolic mediators in the joint,
could be due to the stilbenoids present in the
and by the inflammatory mediators produced
extract, because pinosylvin and monomethyl
by the cells in the cartilage and synovial
pinosylvin, as well as the control compound
membrane. Matrix metalloprotease enzymes,
resveratrol, also had an inhibitory effect on the
especially MMP-1, MMP-3 and MMP-13, are
synthesis of MMP enzymes.
produced by chondrocytes in the OA cartilage
and play a significant role in cartilage matrix
degradation. (Figure 7) Compounds capable
of inhibiting the synthesis of MMP enzymes
are being intensively sought and investigated
4.5 Pine knot extract and its stilbenoid
constituents attenuate the activity
of two major inflammatory signalling
pathways
as potential future drugs to alleviate cartilage
degradation associated with OA.
The cell culture studies were extended in
order to further understand the mechanisms
In the present study, we investigated the
of action of the pine knot extract and its
effects of pine knot extract and its stilbenoid
stilbenoid constituents in inflammatory cells.
constituents on the production of various
Nuclear factor-kB (NF-kB) is an important
catabolic, anabolic and inflammatory factors in
inflammatory
human chondrocytes by using a chondrocyte
known to be activated by various inflammatory
cell line and primary human chondrocytes
stimuli. Once activated and translocated to
isolated from human cartilage tissue from OA
the nucleus, NF-kB is able to augment the
patients removed during joint replacement
transcription of various inflammatory genes,
operations. As can be seen in Table 2, the
including many of those found to be regulated
transcription
factor
that
is
by the pine knot extract and its constituents.
Inhibitors of NF-kB are under development
for the treatment of arthritis and asthma, and
other inflammatory diseases.
To investigate the effects of the pine knot
extract and its stilbenoid compounds on NF-kB
activation and NF-kB dependent transcription,
we generated two different types of reporter
gene containing cell lines. The cells were
transfected with a reporter gene construct,
in which the luciferase gene (which is not
normally expressed in human cells) was linked
to an NF-kB dependent promoter, as shown in
Figure 8A. In those cells, the promoter activity
could be enhanced by inflammatory factors
which are known to activate NF-kB (e.g. LPS,
Figure 7. Pathological changes and mechanisms
in osteoarthritis.
98
IL-1 or TNF), and this in turn could be measured
as increased luciferase mRNA levels or as
Table 2. Effects of pine knot extract and its components pinosylvin and monomethyl pinosylvin as well
as the control stilbenoid resveratrol on the production of matrix metalloprotease enzymes MMP-1, MMP3 and MMP-13 in a human chondrocyte cell line activated with the inflammatory cytokine interleukin 1.
The results are expressed as mean ± SEM; ** indicates p<0.01.
Figure 8. Effects of pine knot extract and its components pinosylvin and monomethyl pinosylvin on
NF-kB mediated transcription. Figure A is a schematic presentation of the cell model generated and
used in the studies. Figure B shows the effects of the pine knot extract and its stilbenoid constituents
pinosylvin and monomethyl pinosylvin as well as the effects of the control stilbenoid resveratrol and an
earlier known NF-kB inhibitor MG132 on NF-kB mediated transcription, which was measured as luciferase
activity in the model described in A. The results are expressed as mean + SEM; ** indicates p<0.01.
99
increased luciferase enzyme activity in the
and anti-inflammatory factor HO-1 in a dose-
cells.
dependent manner. Interestingly, pinosylvin
and monomethyl pinosylvin also enhanced
Figure 8B shows an example of the results of
cellular HO-1 levels, at least when used at
the studies in which the effects of the pine knot
100 μM concentrations, while the effects of
extract and its stilbenoid constituents on NF-
resveratrol were minor. The increased HO-1
kB mediated transcription were investigated.
expression may contribute to or mediate
The pine knot extract significantly inhibited
the inhibitory effect on NF-kB mediated
NF-kB mediated transcription, and the effect
transcription caused by the pine knot extract
was shared by pinosylvin and mono-methyl
and its stilbenoid constituents.
pinosylvin as well as by resveratrol, which was
used as a control stilbenoid.
PI3K/Akt is another major intracellular signalling
pathway involved in inflammation and cancer.
Heme oxygenase 1 (HO-1) is a factor known to
PI3K (phosphoinositide 3 kinase) activation
play a role in cellular defence against oxidative
leads to phosphorylation of Akt, which regulates
stress and to have anti-inflammatory and
the activation of many inflammatory genes.
cytoprotective properties. Those effects are,
Therefore, we were curious to investigate whether
at least partly, mediated through inhibition
the pine knot extract and its bioactive stilbenoid
of NF-kB activation. Therefore, we aimed to
constituents have an effect on the PI3K/Akt
investigate whether the pine knot extract and
pathway in activated inflammatory cells.
its stilbenoid compounds, which were able to
inhibit NF-kB mediated transcription, could
As expected, inflammatory stimuli, such as LPS,
also augment the expression of HO-1.
activated the PI3K/Akt pathway in macrophages,
measured as Akt phosphorylation. The pine
As shown in Figure 9A, the pine knot extract
knot extract inhibited Akt phosphorylation in
enhanced the expression of the cytoprotective
those conditions, and the effect was shared by
Figure 9. Effects of (A) pine knot extract and (B) its components pinosylvin and monomethyl pinosylvin
as well as the control stilbenoid resveratrol on heme oxygenase 1 (HO-1) expression in macrophages
activated with the inflammatory stimulus LPS. Hemin was used as an earlier recognized positive control
compound to enhance HO-1 expression. The results are expressed as mean + SEM; *indicates p<0.05,
** = p<0.01 and *** = p<0.001.
100
the pine stilbenoids pinosylvin and monomethyl
diseases targeted by the research (obesity,
pinosylvin as well as by resveratrol, which was
osteoarthritis, allergy, and cancer) are major
used as a control stilbenoid. An example of
public health problems of increasing incidence,
the results is shown in Figure 10. These results
the impact of which at the individual and
suggest that stilbenoids are responsible for the
societal level is growing substantially along
inhibitory effect of the pine knot extract on the
with their cost to the health care system. Thus,
PI3K/Akt pathway. Furthermore, the studies
there is a clear need for new preventive means
of NF-kB and the PI3K/Akt pathway strongly
and treatment options for these diseases. In
suggest that those mechanisms may explain,
the present project, several health targets
at least partly, the anti-inflammatory properties
and product applications were identified for
of the pine knot extract and its bioactive
further development.
stilbenoids on inflammatory gene expression
and inflammatory responses in vivo.
Finnish wood resources hold vast potential for
the development of novel and innovative high-
of results
value products. This project identified wood
components that are not yet exploited but have
potential to be utilized for the development of
health-promoting high-value products, such as
This project contributes to building a globally
functional foods, nutraceuticals, natural drugs
competitive and unique Finnish knowledge
or pharmaceuticals. The focus was on wood
platform on wood components and their
extracts rich in bioactive components and
potential use as health-promoting agents. The
with broad exploitation potential. This opens
opportunities for the development of new
value chains and business concepts from raw
material supply to further product development
and commercialization, thus helping drive the
renewal of the forest industry.
Figure 10. Effects of pine knot extract and its
components pinosylvin and monomethyl pinosylvin
as well as the control stilbenoid resveratrol
on the PI3K/Akt pathway, measured as Akt
phosphorylation. LY294002 was used as a control
compound known to inhibit PI3K. The results are
expressed as mean + SEM; **indicates p<0.01.
101
6. Networking
The research was carried out in cooperation by the partners, see Table 3. the work package
partners and their roles.
Table 3. Research partner organizations and their research roles.
Work package partner
Stora Enso
Industrial tutor
Chemical modification of wood-derived
compounds.
University of Tampere
Investigation of bioactivity of wood-derived
extracts and compounds in inflammation with
special reference to (osteo)arthritis and allergy
University of Turku
WP leader. Investigation of bioactivity of woodderived extracts and compounds in obesity and
cancer
UPM-Kymmene
Industrial tutor
VTT
Biotechnological modification of wood-derived
compounds.
Composition analysis of wood extracts and their
metabolites.
102
Bromann,
K.,
Toivari,
M.,
Viljanen,
K.,
Vuoristo, A., Ruohonen, L. and Nakari-Setälä,
T. Identification and characterization of a novel
diterpene gene cluster in Aspergillus nidulans.
Plos One, 2012, 7(4):e35450.
Eräsalo, H., Laavola, M., Hämälainen, M.,
Leppänen, T., Nieminen, R. and Moilanen, E.
PI3K inhibitors LY294002 and IC87114 reduce
inflammation in carrageenan-induced paw
edema and down-regulate inflammatory gene
expression in activated macrophages. Basic
and Clinical Pharmacology and Toxicology,
2014 in press.
Laavola, M., Nieminen, R., Leppänen, T.,
Eckerman, C., Holmbom, B. and Moilanen,
E. Pinosylvin and monomethyl pinosylvin,
constituents of extract from knots of Pinus
sylvestris,
reduce
inflammatory
gene
expression and inflammatory response in vivo.
Submitted for publication.
Polari,
L.,
Ojansivu,
P.,
Mäkelä,
S.,
Eckerman, C., Holmbom, B. and Salminen, S.
Galactoglucomannan extracted from spruce
(Picea abies) as a carbohydrate source for
probiotic bacteria. Journal of Agricultural and
Food Chemistry, 2012, 60(44):11037-43.
Qiu, Yaqi. Dietary factors affecting human
aromatase gene reporter expression in normal
tissues and cancer; Focus on mammary gland
and breast cancer. Master’s thesis. Åbo
Akademi University, Dept. of Biosciences. 2013.
Yatkin, E., Polari, L., Laajala, TD., Smeds, A.,
Eckerman, C., Holmbom, B., Saarinen, NM.,
Aittokallio, T. and Mäkelä, S. Novel lignan and
stilbenoid mixture shows anticarcinogenic
efficacy in preclinical PC-3M-luc2 prostate
cancer model. PlosOne 2014, 9(4):e93764.
103
THERMOPLASTIC LIGNIN
AND REINFORCING
CELLULOSE FIBER
COMPOSITES
FOR ADVANCED
BIOCOMPOSITE
APPLICATIONS
CONTACT PERSON – Work Package 3 leader Antti Ojala, [email protected]
Metsä Fibre: Pirkko Liias
Novoplastik: Johannes Heiskanen, Pietari Heiskanen, Merja Lehto
Stora Enso: Kalle Ekman, Janne Pynnönen
University of Helsinki: Juha Fiskari, Ilkka Kilpeläinen, Maarit Lahtinen
University of Jyväskylä: Markku Kataja, Arttu Miettinen
UPM-Kymmene: Mika Hyrylä, Eeva Jernström
VTT Technical Research Centre of Finland: Stina Grönqvist, Karita Kinnunen-Raudaskoski,
Jani Lehmonen, Kalle Nättinen, Lisa Wikström
104
ABSTRACT
The processability and thermomechanical performance of thermoplastic lignin
composites were studied. The aim was to develop processes and materials to enable the
production of composites with high lignin (>50% of the matrix) and wood-based material
content. Processing of the composites was carried out using twin-screw extrusion and
injection moulding techniques. The focus was on softwood kraft lignin, but also lignins
from alkali and hot water extractions were evaluated. To reduce the high glass transition
temperature of kraft lignin and to enhance the ductility of the composites, both external
as well as internal plasticization routes were employed. Thermomechanical (TMP) and
bleached (Fusellu) softwood pulps were used to improve the processability and mechanical
performance of the composites. Materials reinforced with Fusellu demonstrated
slightly higher mechanical performance than the TMP-reinforced composites. The
best performance was obtained using a mixture of acetylated starch (Ac-starch) and
triethyl citrate (TEC) as the external plasticizer and Fusellu reinforcements. Acetylation,
hydroxypropylation and palmitic acid grafting methods were used to internally plasticize
kraft lignin. Of the internally plasticized materials, composites with the Ac-starch-TEC
plasticized acetylated lignin (Acet-L) matrix and Fusellu reinforcement gave the best
mechanical properties. The fabricated composites had a tensile strength of 35 MPa and
modulus of 6.6 GPa. The overall content of the wood-based materials was 70%. The
structure of the composites was characterized using X-ray computed microtomography
(X-µCT). The focus of the study was on fibre dispersion and breakage. The fibre dispersion
in the thermoplastic lignin matrices was observed to be good. However, the processing
conditions had a significant detrimental impact on fibre length.
Keywords:
thermoplastic lignin, injection moulding, thermomechanical pulp, bleached pulp,
X-ray microtomography
105
1. Background
2. Objectives
Modern biorefineries (e.g. pulping mills and
The aim of the research was to develop
bioethanol plants) using lignocellulosic feedstocks
technologies and competences enabling the
produce as a by-product large amounts of lignin,
production of novel biocomposite materials
which is currently almost exclusively burned
in which wood-derived lignin and cellulose
for energy. For example, it is estimated that
fibre are the main constituents. For best
the annual global production of lignin in kraft
performance, both the fibre and lignin fractions
pulp mills exceeds 50 million tonnes. Lignin is
were modified. Modification of the lignin fraction
therefore a vastly underutilized resource.
included internal and external plasticization for
improved ductility and processability. Chemical
Global annual plastics production currently
modifications of the fibres were targeted at
stands at around 250 million tonnes, of which
enhancing bonding with the matrix lignin and
thermoplastic materials account for 65%. By
the subsequent reinforcement effect.
far the largest thermoplastic segments are
petroleum-based PE, PP and PVC at 33%,
The target application sectors were construction
21% and 17%, respectively. The share of non-
and furniture.
petroleum based materials remains highly
marginal (<1% of all produced thermoplastics).
Furthermore, current renewable materials are
almost exclusively based on starch, and thus
compete directly with global food production.
The main task was to evaluate the potential
There is therefore a clear demand for low-
of lignin as a thermoplastic matrix material in
cost non-food based plastics from renewable
wood pulp reinforced composites. The focus
feedstock. One of the most promising candidates
was on the processability of lignin and the
is thermoplastic lignin – the world’s second most
mechanical performance of the composites.
abundant polymer after cellulose.
Softwood
kraft
lignin
(LignoBoost™)
was
used as the main component, in addition
Initial trials on kraft lignin were carried out in
to which hot water extracted and alkali
the FuBio programme (2009-2011), in which the
lignins and commercial lignins were also
thermoplastic properties and processability of
tested. The reinforcing wood fibres were
lignin were briefly evaluated. Based on these
chemically bleached softwood pulp (Fusellu)
promising results, it was decided to dedicate a
and thermomechanical softwood pulp (TMP)
separate work package to thermoplastic lignin
supplied by Metsä Fibre and UPM, respectively.
composites under the FuBio Joint Research 2
Additionally, PHWE extracted and ionic liquid
programme launched in 2011.
extracted fibres supplied by Metla were
evaluated in the composites.
The research was divided into the following
four tasks:
• Development of lignin modifications
(“internal plasticization”) with the goal of
reducing glass transition temperature (Tg )
and brittleness.
106
4. Results
• Chemical and enzymatic modification of
fibres with the goal of enhanced fibre and
4.1 Structural and thermal
characterization of lignins
matrix lignin interaction.
• Manufacturing of the composites. Two
simultaneous routes were employed: i)
selection and development of the actual
The main lignin source was softwood kraft
processes and equipment needed for
lignin LignoBoost (LB, purity 96.7%) supplied by
manufacturing lignin-fibre composite
Metso. Table 1 shows the chemical composition
compounds and ii) iterative development
of LB determined by the 31P NMR method. The
of the lignin-fibre composite compounds at
total amount of hydroxyl groups (mmol/g)
laboratory and pilot scale.
was 5.28, of which 3.39 were phenolic and the
rest were aliphatic, condensed or carboxylic
• Structural characterization of the
composites using X-ray computed
acid. Additionally, the molecular weight (Mw)
microtomography (X-µCT)
distribution for LB as well as for alkali lignin
(AL) and pressurized hot water extracted lignin
Figure 1 shows the key processing steps
(PHWE) were determined using GPC methods.
involved
thermoplastic
The results of the GPC analyses are presented
lignin composites. In the first step, the
in Table 2. LB has the highest Mw at 4450 Da.
extracted lignin was plasticized to improve its
AL and PHWE have Mws of 2800 and 1700 Da,
processability (i.e. to reduce the glass transition
respectively, clearly lower than that of LB.
in
producing
the
temperature, Tg ). Two different approaches,
internal and external plasticization, were
Thermal properties of the lignin samples were
used. In the second step, plasticized lignin
analysed using differential scanning calorimetry
was processed with wood pulp to produce
(DSC). Figure 2 and Table 3 present the results
wood fibre reinforced thermoplastic lignin
of the DSC scans. All lignin samples show two
composites. Finally, the composite parts were
glass transition points (Tg) at 60-70 °C (Tg1) and
produced by injection moulding.
at 100-180 °C (Tg2). LB has the highest Tg2 at 152.5
Figure 1. Schematic presentation of the processing of lignin composites.
Table 1. Amount of different hydroxyl group species (mmol/g) in lignin samples as detected by NMR .
Lignin
Aliphatic
OH
Carboxylic
acid
Condensed
S
G
Ca
Phenolic
OH
Total
OH
LB
1.60
0.29
1.46
0.00
1.89
0.05
3.39
5.28
107
Table 2. Molar mass distributions of the LB, AL and PHWE samples.
Sample
Mn (Daltons)
Mw (Daltons)
Polydispersity
LB
2289
4450
1.94
AL
1800
2800
1.51
PHWE
1200
1700
1.36
Figure 2. Second heating cycle scans for the AL (red), PHWE (green) and LB (blue) samples. The heating
ramp was 10 °C/min from -50 °C to 200 °C.
Table 3. Results of the thermal analyses for the LB, AL and PHWE lignins as well as for the internally
plasticized PL, HPL and Ace-L lignins.
Lignin
108
Description
Tg1 / °C
Tg2 / °C
Tdeg10% / °C
LB
Softwood kraft lignin
68.5
152.5
328.5
PHWE
Hardwood PHWE lignin
71.8
120.8
282.0
AL
Softwood alkali lignin
61.0
102.4
282.5
PL
Palmitic acid modified
LB lignin
n/d
n/d
245.1
HPL
Hydroxypropylated
LB lignin
63.0
112.4
300.9
Acet-L
Acetylated LB lignin
46.0
101.4
272.6
°C, whereas AL and PHWE have Tg2 at 102.4 and
Together with external plasticization, inter-
120.8 °C, respectively. Note that the Tg2 of the
nally plasticized lignins were evaluated as the
PHWE sample is substantially higher than that
matrix materials in the composites. The aim
for AL, although the Mw of PHWE is clearly lower.
of the internal plasticization was to reduce
the high Tg of the native kraft lignin (LB) and,
The thermal stabilities of the lignin samples
successively, to improve the ductility of the
were determined using thermogravimetric
composites. Palmitic acid grafted lignin (PL),
analysis (TGA). The results are presented in
hydroxypropylated lignin (HPL) and acetylat-
Table 3. LB has the highest thermal stability of
ed lignin (Acet-L) were selected as the main
the analysed samples. The point at which 10%
target modifications. The samples were syn-
of the sample weight is lost (Tdeg10) is observed
thesized using LB as the starting material.
at 329 °C. AL and PHWE are, in turn, less sta-
Based on the
ble with Tdeg10 at 283 and 282 °C, respectively.
of substitution (DS) of the aromatic and alkyl
Compared to the DSC analyses, it is clear that
hydroxyl groups for HPL, PL and Acet-L were
the degradation temperatures for the lignin
100, 88, and 97%, respectively.
31
P NMR analyses the degree
samples are significantly higher than the softening temperatures. The degradation tem-
The results of the TGA analyses for the modified
peratures are also significantly higher than the
lignins are presented in Table 3. Compared to
corresponding temperatures for the employed
native LB, the modified lignins have somewhat
wood pulps (approx. 220 °C). Hence, we can
reduced thermal stabilities. The Tdeg10 was
conclude that the lignins are suitable for melt
observed for the PL, HPL and Acet-L samples
processing with the wood pulps.
at 245, 301 and 273 °C, respectively.
Figure 3. Second heating cycle scans for the HPL (green), PL (red) and Acet-L (blue) samples. The heating
ramp was 10 °C/min.
109
The main purpose of the internal plasticization
Based on the preliminary laboratory scale
was to reduce the softening temperatures of
results, the most interesting materials and their
lignin and hence improve the ductility of the
combinations were further evaluated using a
composites. Figure 3 presents the results of
continuous pilot scale process. Figure 5 shows
the DSC scans for the modified lignins. The
the main processing steps in the manufacture
PL sample gives a complex graph with endo-
of thermoplastic lignin composites at the pilot
thermic peaks at 0.4 °C and 47.3 °C and a very
scale. Compacting was used to reduce the large
weak endothermic decline at 78.7 °C. It is un-
volume of the pulps prior to compounding.
clear whether some of these peaks are related
The
to Tg . In the HPL and Acet-L scans, the clear
approximately 15mm x 4mm in size, after which
fibres
were
compacted
into
pellets
endothermic declines at 112 and 101 °C, respec-
the fibre pellets, lignin, plasticizers and possible
tively, are attributed to Tg2 . Furthermore, the
additives were thermally mixed to form uniform
two weak endothermic declines at 63 (HPL)
compounds. The compounds were prepared
and 46 (Acet-L) °C are attributed to Tg1 .
by using a twin-screw extruder (ZE25 x 48D,
Berstorff GmbH). Finally, the compounds were
4.2 Processing of lignin composites
injection moulded as test specimens using an
Engel (ES 200/50 HL) and mechanically tested
Thermoplastic lignin composites were processed
using an Instron tensile tester.
at two different size scales. Preliminary testing of
the new materials and the material combination
The charpy method was used to measure the
was carried out at the laboratory scale. Lignin,
impact strengths for the un-notched samples.
additives and fibres were thermally mixed in
a Brabender Plasticorder batch mixer with a
4.3 Thermoplastic lignin composites
sample size of 44 g. The test specimens (see
Figure 4) were then injection moulded using a
Various external plasticizers for LB were
MiniJet (ThermoHaake) and mechanically tested
tested
using a tensile tester (Instron).
Based on the preliminary trials, polyethylene
in
laboratory
scale
experiments.
a)
b)
Figure 4. Lignin composite in a Brabender batch mixer (a). Two tensile test specimens prepared at
laboratory and pilot scale (b).
Figure 5. Processing steps in the pilot scale manufacture of lignin composites.
110
glycol (PEG) was observed to give the best
water soluble, which significantly reduces
processability and tensile properties. Samples
the weather resistance of the composites.
with TMP and Fusellu reinforcements were
Therefore, a new plasticizer for lignin based
produced. The TMP-reinforced composites had
on a mixture of starch acetate (Ac-starch) and
somewhat higher mechanical performance
triethyl citrate (TEC) was developed. Previous
than that of Fusellu. To further evaluate
studies with flax fibre reinforced Ac-starch-
the processability of kraft lignin, externally
TEC composites have shown that the mixture
plasticized composites based on LB, PEG and
has excellent compatibility with cellulosic
TMP reinforcements were fabricated at the
fibres. In addition, Ac-starch and TEC can be
pilot scale. To determine optimal LB lignin/
obtained from renewable sources, and they
TMP/PEG ratios, a series of composites with
are scarcely soluble in water. Preliminary
different compositions were fabricated. The
evaluation
best performing composites had a composition
ratio was performed at the laboratory scale
(by weight) of 49% LB lignin, 30% TMP and
followed by more comprehensive pilot scale
21% PEG. These composites had a tensile
trials. The optimal Ac-starch/TEC ratio was
strength of 28.8 MPa, Young’s modulus of 5.1
found to be approximately 60/40 (by weight).
of
the
optimal
Ac-starch/TEC
GPa and impact strength of 4.6 kJ /m . Further
2
increases in TMP content did not improve
After the preliminary evaluations, the effect
the tensile properties. Additionally, higher
of lignin content was studied at the pilot
PEG contents (relative to lignin) resulted in
scale (Figure 6). In all prepared samples, the
improved impact strength but also significant
Ac-starch/TEC ratio was 60/40 and the TMP
reductions in tensile strength and stiffness.
fibre content was 20%. Tensile strength of
the composites was found to decrease with
PEG has two major drawbacks as a plasticizer:
increasing lignin content. The composites with
1) it is of non-renewable origin and 2) it is highly
32% lignin demonstrated a tensile strength
Figure 6. Effect of lignin content on the mechanical properties of Ac-starch-TEC plasticized composites.
The Ac-starch/TEC ratio was 60/40 and the TMP content was 20% in all cases. The best PEG-plasticized
composites (49% LB lignin/30% TMP/21% PEG) are shown as a reference.
111
of 26.6 MPa, whereas increasing the lignin
of the initial dry weight. Furthermore, the
content to 49% decreased the strength to
FTIR analysis revealed that the dissolved solid
19.6 MPa. In turn, stiffness of the composites
was almost exclusively PEG. Thus, the large
improved
content.
water uptake (weight increase) of the PEG-
Compared to the PEG-plasticized composites,
plasticized composites can be explained by
the tensile strength of the Ac-starch-TEC
the dissolution of the highly water soluble PEG
plasticized composites were comparable.
component and the successive formation of a
with
increasing
lignin
hollow structure that readily absorbs water. In
Water absorption
turn, the dissolved solid from the Ac-starch-
To study weather stability, a series of water
TEC plasticized samples was only 0.3% of the
absorption trials was performed for the
initial dry weight.
injection moulded PEG (49% LB/21% PEG/30%
TMP)
and
Ac-starch-TEC
Ac-starch-TEC/27.5%
(45%
TMP)
LB/27.5%
Effect of lignin type on performance
plasticized
The properties of AL and PHWE lignins
composites. The composites were immersed
supplied by Metla and a commercial alkali
in water and the weight changes were
lignin (GV) from GreenValue in composites
monitored over a period of two weeks. Figure
were evaluated. GV is extracted from plant
7 presents the results of the trials. During the
feedstock by an aqueous sodium hydroxide
first week, the weight of the PEG-plasticized
method.
composites increased rapidly until levelling
reinforcement and PEG plasticization of AL
off at 41% after 1.5 weeks. In turn, Ac-starch-
and GV were fabricated at laboratory scale.
TEC plasticized composites demonstrated
Figure 8 presents the results of the tensile
very slow water uptake with a weight increase
tests. Compared to the composites with
of only 6% after two weeks. To evaluate the
the LB matrix, the samples with GV and AL
dissolved material, the used water bath
show reduced tensile strengths and modulus,
solutions were collected and evaporated. The
whereas the strains at break are significantly
residual solids were weighted and analysed
increased. The notably high ductility of the AL
with FTIR. The amount of dissolved material
composites is attributed to the low Tg2 of the
from the PEG-plasticized samples was 7.5%
material.
Identical
samples
with
TMP
Figure 7. Results of the water absorption tests for PEG (diamonds) and Ac-starch-TEC (circles) plasticized
composites.
112
Figure 8. Tensile properties of the PEG and Ac-starch-TEC plasticized composites with different lignin
matrices.
Moreover, composites with Ac-starch-TEC
corresponding AL composites. The viscosity
plasticization were fabricated at laboratory
of the LB composites was so high that the
scale using AL and PHWE lignins as the matrix
composites could not be injection moulded.
materials. Compared to PEG plasticization,
Ac-starch-TEC
plasticized
AL
composites
Following
the
promising
laboratory
scale
show higher tensile strength and modulus,
tests, AL and PHWE lignins were also tested
whereas the strain at break is lower. In
at the pilot scale. Figure 9 shows the results
turn, the Ac-starch-TEC plasticized PHWE
for the Ac-starch-TEC plasticized composites.
composites
tensile
The properties are highly similar between the
strength and modulus with respect to the
samples. The only exception is observed in
have
notably
higher
Figure 9. Mechanical properties of composites based on the LB, AL and PHWE matrices. In all cases,
the composition was 41% lignin/39% Ac-starch-TEC/20% TMP. The composites were fabricated at
the pilot scale.
113
impact strength, which was 2.1 and 2.3 kJ/m2 for
plasticizers such as PEG is a significant
the AL, PHWE composites, respectively, and 1.6
limitation on the wider utilization of the
kJ/m2 for the composites with the LB matrix.
material. One possibility for improving the
stability is to reduce the content of free PEG.
Composites based on acetylated lignin
However, a simple reduction of PEG content in
In addition to external plasticization, internally
the composites leads to significantly weaker
modified (i.e. internally plasticized) lignins
tensile properties, such as lower ductility
were also tested in composites. The selected
and increased brittleness. To circumvent this
modification
acetylation,
problem and to optimize the compatibility
hydroxypropylation and palmitic acid grafting.
between the fibres and the matrix, TMP was
The aim of internal plasticization was to
chemically cross-linked with PEG diepoxide
replace the external plasticizers or, at least,
[PEGDE, polyethylene glycol (200) diglycidyl
to significantly reduce the need for external
ether, Polysciences, Inc.] to produce PEG-
plasticizers. The composites based on palmitic
grafted TMP.
methods
were
acid grafted lignin (PL) were processable
However,
For the composite trials, several samples
processing of the composites based on the
with different degrees of cross-linking were
acetylated (Acet-L) and the hydroxypropylated
prepared. The results of tensile tests on
(HPL)
possible
two samples with a lower (6%) and a higher
without external plasticizers. Moreover, both
(20%) degree of cross-linking are shown in
modifications required the same amount of
Figure 10. The details of the compounded
Ac-starch-TEC plasticizer as the composites
samples are presented in Table 4. Based on
based on unmodified LB.
these results, the tensile strengths were
without
external
lignin
plasticizers.
matrices
was
not
significantly increased when the sample
In the preliminary laboratory scale tests, the
had a higher degree of cross-linking (20%).
best performance was obtained with Acet-L
Furthermore, a lower degree of cross-linking
composites.
therefore
(6%) had a positive effect. In comparison
selected for closer evaluation in pilot scale trials
with the reference sample, after PEG grafting
using Ac-starch-TEC as the external plasticizer.
the tensile strength improved by 45%.
Fusellu was employed as the reinforcing fibre
Simultaneously, the amount of free PEG could
as it gave generally better results in Ac-starch-
be reduced by 4 wt% without compromising
TEC plasticized systems compared to TMP.
ductility or stiffness, which improved by 23%.
This
material
was
The composites with the Acet-L matrix had
higher improved properties compared to the
unmodified LB composites. Composites with
36% Acet-L, 34% Ac-starch-TEC and 30%
4.4 Structural characterization
of the composites using X-ray
microtomography
Fusellu had the best mechanical properties,
and their recorded tensile strength (35 MPa)
The utilized processing techniques (twin-screw
was the highest of all the injection moulded
extrusion and injection moulding) expose
composites. In addition, their impact strength
the fibres to harsh conditions such as high
(3.8 kJ/m2) was the highest of all the Ac-starch-
temperatures and shear forces. The process is
TEC plasticized composites.
particularly harmful to cellulosic fibres, which
have been observed to undergo substantial
114
Composites based on chemically modified TMP
decomposition.
The low water stability of typical lignin
especially problematic as this is one of the key
Reduced
fibre
length
is
Figure 10. The effect of cross-linking with PEG diepoxide on strength properties of the compounded
material at laboratory scale. The amounts of different components and the degree of cross-linking are
shown in Table 4.
Table 4. Composition of the compounded samples cross-linked with PEG diepoxide (strength test
results are presented in Fig. 10).
Sample
Lignins
wt-%
Plasticiser
wt-%
Fibre
wt-%
FU88, Ref
LB
56
PEG
24
TMP
20
FU112
LB
56
PEG
22,8
TMP-g-PEG (6%)
21,2
FU113
LB
56
PEG
20
TMP-g-PEG (20%) 24
factors defining the mechanical performance
visible and some fibre agglomerates (white
of the reinforced composites. Particularly
lumps) can be seen indicating poor dispersion.
challenging is the low impact strength, which
limits the utilization of lignin composites in
Before
more demanding applications, such as in
geometrical structure of the samples can be
vehicles. Therefore, the effect of processing
made, the images must be pre-processed to
conditions on the reinforcing fibres in the
remove spurious noise. Different methods for
thermoplastic lignin composites was analysed
noise removal filtering were tested. The best
using
microtomography
of these appear to be simple Gaussian filtering
(X-µCT). Particularly, the focus was on fibre
and variance weighted mean filtering. In the
length and distribution in the matrix.
first method, the final value of a pixel is the
X-ray
computed
quantitative
assessments
of
the
weighted mean of the surrounding pixel values
The characterization study began with an
where the weight function is a Gaussian. In the
initial search of imaging parameters. This
second method, the mean around a pixel is
process, done using thermoplastic lignin
weighted using the inverse of local variance
composite materials, indicated that the image
around the pixel, thus reducing blurring of
contrast between fibre and matrix is sufficient
sharp edges. The method of choice depends
to enable the phases to be differentiated
on the quality of the original image and the
from each other. Figure 11 shows a composite
type of analysis carried out on the sample.
material sample consisting of a PEG-plasticized
LB matrix and 25% TMP. The fibres are clearly
The methods of analysis found to be most
115
a)
b)
c)
Figure 11. X-µCT images of a PEG-plasticized lignin/20% TMP sample processed at laboratory scale. Crosssection of the sample (a) shows fibres visible as brighter areas. Two 3D visualizations of the same sample
with different, b) low and c) high resolution. Large white areas in the middle image are fibre agglomerates.
useful for the materials include measurement
approximate diameter). All of the methods
of
yield the distribution of the measured value
fibre
length
using
a
granulometric
technique, measurement of fibre orientation
(e.g. fibre length distribution).
using the structure tensor method, and
measurement of fibre cross-sectional shape
The homogeneity of the fibre volume fraction
parameters using a novel technique where
in the PEG-plasticized LB matrix with 20%
local fibre orientation information is used to
TMP tensile test specimens was analysed
construct 2-dimensional slices of fibres in
(See Figure 12). Depending on the sampling
the direction of their orientation. The slices
position, the measured fibre volume fraction
can then be used to measure e.g. the cross-
was found to increase such that the volume
sectional area of fibres or shape descriptors
fraction is lowest close to the injection cavity
of the fibre cross-sections (e.g. circularity or
and highest at the other end of the specimen.
a)
b)
Figure 12. Volume fraction of fibres in different locations (a) in the thermoplastic lignin test specimen (b).
The injection direction was from “broken end” to “non-broken end”.
116
Following these results, further tomographic
To compare the present results with such
analyses were conducted on samples taken
measurements, the mean fibre lengths were
from the middle part of the specimen.
also determined for the L > 500 µm fractions. The
results indicate mean fibre lengths in the range
It was observed that the aspect ratio of the fibres
650 µm – 900 µm for the tensile test specimens
decreases significantly when the intact fibres
and 1500 µm and 960 µm for intact chemical
are processed as injection moulded specimens.
and mechanical pulps, respectively (see Figure
A good example of the results is given in Figure
14). It is thus evident that the pelletization,
13, where the aspect ratio distributions and the
compounding and injection moulding processes
corresponding means for pulp fibres, pelletized
significantly increase the fraction of fines,
fibres and the final injection moulded tensile test
possibly decreasing the mechanical properties
specimen are shown. The material in FUMO68
of the composite materials.
consisted of 20% Fusellu, 39% Ac-starch-TEC
and 41% lignin. The reduction in mean aspect
A
ratio is clearly visible both in the distributions
mechanisms of composite materials is whether
key
question
concerning
the
fracture
and in the means.
the reinforcement fibres are mainly broken at
the fracture surface, or whether some of them
The mean fibre length of the injection moulded
are pulled out of the matrix at fracture. The latter
specimens was in the range 150 µm–300 µm,
case would be indicative of inadequate bonding
and the mean aspect ratio in the range 10 – 20
between the matrix and the fibres. The fracture
µm (see Figures 14 and 15). The composition
surfaces of two material samples manufactured
of the composites is presented in Table 5. The
in this project, FUMO18 (20% TMP in PEG-
mean fibre length of the raw chemical (Fusellu)
plasticized LB matrix) and FUMO39 (20% TMP
and mechanical (TMP) pulp, measured with the
in Ac-starch-TEC plasticized LB matrix), were
X-µCT technique, was 1100 µm and 600 µm,
studied using X-µCT imaging. Based on visual
respectively. The decrease in fibre length due
inspection of the images, it appears that in both
to processing is thus very large.
of the studied samples only a minor proportion of
fibres were pulled out, with most remaining firmly
In some manual methods fibres less than 500 µm
attached to the matrix, see Figure 16. Hence,
in length (typically classified as “fines”) are not
we can conclude that the fibres have a strong
included in the mean fibre length determination.
positive reinforcing effect on the composites.
a)
b)
Figure 13. a) Length/diameter distributions estimated for FUMO68 b) Mean length/diameter
distributions for FUMO68. Mean values are calculated based on both major (d1) and minor (d2)
diameters of fibres, but the distributions are shown only for L/ d1.
117
Figure 14. Mean fibre length of the selected composites, raw fibres and pellets. Means are calculated
from full data (blue bars) and from the >500 µm length fraction (red bars).
Figure 15. Mean fibre aspect ratio of the selected composites, raw fibres and fibre pellets. The crosssection of the fibre has been approximated with an ellipse, where d1 refers to the length of the major axis
and d2 to the length of the minor axis of the ellipse.
Table 5. Composition of the composites. Fibre weight fraction was 20% in all cases.
Sample
Fibre type
Lignin wt-%
Acetylated
TEC wt-%
starch wt-%
118
FUMO39
TMP
40.8
23.2
16.0
FUMO68
Fusellu
40.8
23.2
16.0
a)
b)
Figure 16. Cross-sectional X-µCT slices of FUMO18 (a) and FUMO39 (b). Dark, medium grey and light
grey colours indicate air, matrix and fibres, respectively. Only a few pulled-out fibres and micro-cracks
extending in the bulk material are visible.
4.5 Demonstrators
Fusellu reinforcements). Two different moulds
were employed to produce the parts. The
The processability of the thermoplastic lignin
“spacer mould” is a commercial mould used
composites was demonstrated at VTT by
to manufacture complex, thin-walled parts
injection moulding parts using commercial
employed in concrete casting (a). The other
moulds provided by Rinotop (Figure 17). The
mould was a “ball mould” used for producing
demonstrator parts were prepared using
knobs for skipping ropes (b). The ball mould
the best material combinations (PEG as well
has thick walls setting special requirements
as Ac-starch-TEC plasticized LB matrix and
for the heat conductivity of the material.
a)
b)
Figure 17. Injection moulded demonstrator parts with wood-derived material contents up to 77%.
119
of results
In this project, novel thermoplastic lignin
potential is substantial, and furthermore, large
composites
pulp
quantities of lignin are commercially available
of
after the recent introduction of the LignoBoost
thermoplastic lignin was demonstrated using
technology. The results of this work serve as
typical processing equipment, such as twin-
a platform for further development of high-
screw extruders and injection moulders.
performance composite materials based on
The tensile properties of the lignin composites
thermoplastic lignin.
were
reinforced
developed.
The
with
wood
processability
are close to its main competitors: wood fibre
composites
with
petroleum-based
matrix
polymers. Therefore, the potential application
6. Networking
areas for the lignin composites are the same
as for the aforementioned polymers and
The research was carried out jointly by
reinforced composites. These areas include
research organizations and Finnish forest
the construction (e.g. decking, fencing, window
cluster companies. Table 6 presents the
frames), furniture (e.g. chairs, tables, cupboards)
partners and their role in the research.
and automotive (e.g. interior parts) industries.
Lignin
samples
and
related
mechanical
The most promising target applications with
performance data were exchanged between
the current material performance profile are
the
foreseen to be found in construction. At present,
(Canada) during the project.
project
partners
and
FPinnovations
the inadequate impact strength of the injection
moulded composites limits the utilization of
the material in more demanding applications,
such as in vehicles or furniture. However, the
Metsä Fibre
Industrial tutor. Supplier of bleached softwood pulp.
Novoplastik
Testing and evaluation of composite samples.
Stora Enso
Industrial tutor
Chemical activation and modification of fibres enabling
binding with matrix lignin in composite materials.
Characterization and analysis of composites by X-ray
computed microtomography.
UPM-Kymmene
Work Package Coordinator. Supplier of thermomechanical
softwood pulp.
VTT
WP leader. Processing and production of thermoplastic
lignin composites. Chemical modification of lignin and
enzymatic modification of fibres.
120
Lahtinen, M., Ojala, A., Wikström, L., Hietala,
S., Nättinen, K., Fiskari, J. and Kilpeläinen, I.
Injection-molded fiber-reinforced lignin composites from chemically modified thermomechanical pulp (TMP) fibers, in preparation.
Miettinen, A., Joffe, R., Madsen, B., Nättinen, K. and Kataja, M. Quantitative analysis of
length-diameter distribution and cross-sectional properties of fibers from three-dimensional tomographic images, Proceedings of
the 34th Risø International Symposium on Materials Science, 2013.
Miettinen, A., Ojala, A., Wikström, L., Joffe, R.,
Madsen, B., Nättinen, K. and Kataja, M. Nondestructive automatic determination of aspect
ratio and cross-sectional properties of fibres,
in preparation.
Myllymäki, T. Ligniinin rakenne ja kemiallinen
muokkaus, Master’s thesis, University of Helsinki, 2014.
Nättinen, K., Kouisni, L., Paleologou, M., Wikström, L. von Weymarn, N. and Browne, T.
Composites of kraft lignin, Poster presentation
together with FPInnovations in NWBC, Helsinki, 2012.
Ojala, A., Wikström, L., Lehmonen, J. and Nättinen, K. Foam-laid formed thermo-mouldable
nonwovens, Proceedings of Composites Australia and the CRC for Advanced Composite
Structures, Newcastle, Australia, 2014.
121
BIOREFINERY
PRODUCTS
INITIAL PROCESS PILOTING AND
MATERIAL PROTOTYPE PRODUCTION
IN THE CASE OF BARRIERS,
3D-MOULDABLE PACKAGING
AND FILTERS
CONTACT PERSON – Work Package 4 leader Jonas Hartman, [email protected]
Aalto University: Ramarao Abburi, Ilari Filpponen, Jiagi Guo, Karoliina Junka, Janne Laine,
Alexey Khakalo, Eve Saarikoski, Jukka Seppälä, Ola Sundman, Monika Österberg
Kemira: Mari Ojanen, Reetta Strengell, Tarja Turkki
Lappeenranta University of Technology: Kaj Backfolk, Henry Lindell, Daria Nevstrueva,
Arto Pihlajamäki, Sami-Seppo Ovaska, Esa Saukkonen, Panu Tanninen
Metsä Board: Pekka Suokas
Metsä Fibre: Pirkko Liias, Raili Koponen
Stora Enso: Mari Hiltunen, Outi Kylliäinen, Titta Lammi, Jari Räsänen
Tampere University of Technology: Hanna Christophliemk, Johanna Lahti
University of Helsinki: Juha Fiskari, Susanna Heikkinen, Pirkko Karhunen, Ilkka Kilpeläinen,
Sirkka-Liisa Maunu, Kirsi Mikkonen, Pirita Rämänen, Joonas Siirilä, Maija Tenkanen
University of Oulu: Aleksi Kolehmainen, Henrikki Liimatainen, Juho Sirviö, Miikka Visanko
UPM-Kymmene: Harri Kosonen, Leena Kunnas, Jutta Nuortila-Jokinen, Irmeli Sinisalo, Heli Viik
Valmet: Ismo Mäkinen, Pasi Nurminen, Ari Puurtinen, Peter Rosenberg, Timo Sutela
VTT Technical Research Centre of Finland: Martta Asikainen, Marie Gestranius, Antti Grönroos,
Minna Hakalahti, Ali Harlin, Pirjo Heikkilä, Juha Heikkinen, Jaakko Hiltunen, Juha Houni, Petri Jetsu,
Saila Jämsä, Timo Kaljunen, Kari Kammiovirta, Annaleena Kokko, Hanna Koskela, Vesa Kunnari,
Hanna Kyllönen, Christiane Laine, Marjo Määttänen, Heikki Pajari, Jaakko Pere, Pentti Pirkonen,
Pauliina Pitkänen, Hille Rautkoski, Elias Retulainen, Erkki Salo, Harri Setälä, Asko Sneck, Riku Talja,
Tekla Tammelin, Alexey Vishtal
Åbo Akademi University: Pedro Fardim, Jasmina Obradovic, Joanna Narewska, Victor Kisonen,
Stefan Willför
122
ABSTRACT
Demonstration and piloting under the title “Improving traditional fibre products” focused
on multilayer barrier packaging, 3D-mouldable packaging and new filter materials.
Different types of biobarriers were successfully prepared and coated as water dispersions
on precoated base board. The biopolymer-coated webs were also extrusion coated
and finally converted into tray form. Six different types of bio-based derivatives were
developed and tested during the project. The tested materials were modified GGM,
modified xylan, TOFA esters and TOFA alkyd acrylates, dialdehyde cellulose and DAC
alginates and cellulose-copolymer blends. Good grease barrier properties were obtained
in several barrier material groups. Additional studies on the effect of the base substrate
fibre composition revealed that the hemicellulose content of the base substrate affects
the convertability of the paperboard and indicated changes in the dispersion coating holdout and grease resistance of dispersion-coated paper.
In the case of 3D-mouldable packaging, the maximum extensibility obtained for the paper
was around 21% when the polymer dosage was 8%. In-plane compaction increased
extensibility up to 35% in the machine direction. Gelatin effectively improved the
extensibility and tensile strength of the paper and readily adsorbed on the fibres. In order
to enhance the effects, a combination of several chemicals is possible. The treatments are
compatible with current papermaking environments and can be used for the production
of food packaging materials. The convertability of the produced paper materials was
demonstrated in all main forming process types.
Several different new filter materials and manufacturing methods were tested. The results
obtained with some of the demo materials were very promising. Cellulose membrane cast
from ionic liquid was produced for industrial trials and for comparison with commercial
references. Retentions of the studied sample were similar or slightly lower than those
of the commercial references and in general the demo sample showed very stable but
somewhat lower flux in all tested effluents compared to the commercial membranes.
Dicarboxylic acid cellulose (DCC) nanofibre-coated membranes gave promising results.
The vacuum filtration method of producing the samples proved effective at the laboratory
scale, indicating that efficient production of larger membranes, for example by roll-to-roll
coating, could be achieved.
Initial process piloting and material prototype production gained wide interest from the
partner companies. Each of the three product groups had an engaged group of industrial
tutors whose input focused the research and contributed considerably to successfully
improving on conventional fibre products.
Keywords:
3D-forming, biobarrier, filter, forging, formability, membrane, moldability, multilayer barrier,
packaging
123
1. Background
renewable material that has certain advantages
over
plastic-based
materials.
However,
There is a fast-growing need to find replacements
fibre-based packaging materials cannot yet
for oil-based products. Increasing demand
compete with plastic packaging in terms of
for packaging creates opportunities for bio-
convertability or package design – fibre-based
based barrier materials that can be produced
packaging exists in rather simple geometrical
from industrial sidestreams, such as from
forms, whereas plastics can be formed into a
paper and board production. The replacement
vast variety of shapes. The main limiting factor
of oil-based products with products derived
for the production of advanced 3D shapes from
from natural sources has been the focus of
paperboard is its poor formability, i.e. its limited
intensive research in recent years. Due to their
ability to withstand certain types of plastic
renewability, biocompatibility, biodegradability,
deformation without damage.
wide availability and non-toxicity, natural biobased products offer a sustainable means
Formability is the ability of a material to be
of obtaining chemicals and materials and
formed
replacing non-renewable resources. One such
forming processes such as hot pressing, vacuum
important group of biorenewable products is
forming,
biopolymers, including polysaccharides, among
formability of fibres and paper is primarily limited
which cellulose, hemicellulose and starch have
by poor elongation, which is typically below 5%.
been extensively studied. Due to their positive
Formability determines the maximum depth
properties compared to oil-based materials,
of shapes and, to certain extent, the material
one of the most promising target applications
appearance. The forming process and process
of biopolymers is in environmentally friendly
variables (including moisture and temperature)
food packaging materials.
also play a central role in formability.
The focus of the FuBio Joint Research 2
Membranes
programme was on biomass fractionation and
materials
the development of current and new biorefinery
pass through whilst rejecting others. Natural
products. The work was based on the research
membranes
results of the first FuBio programme targeting
in
the main fractions of wood (e.g. cellulose,
although the use of artificial membranes has
hemicelluloses), in which several bio-based
become established in recent decades in a
polymers and polymer blends were developed
wide range of separation processes. The first
for a range of interesting applications. These
artificial membranes were made using the
include dialdehyde cellulose, which is a cellulose
cellulose-based
derivate produced by a regioselective oxidation
Today,
of cellulose using periodate as an oxidation agent,
cellulose acetate and nitrate, are widely used
modified hemicelluloses (galactoglucomannan
in microporous membranes for micro- (MF)
and xylan), tall oil including alkyd-acrylate
and ultra-filtration (UF) and haemodialysis.
hybrid polymers and tall-oil modified cellulose
In addition cellulose-based membranes can
as well cellulose-polyethylene copolymer blends
be used in gas separation as dense, non-
(CePE).
porous films. Cellulose membranes can be
into
complex
stamping
many
are
allowing
or
certain
an
material
The
barrier
compounds
important
membrane
cellulose-based
through
deep-drawing.
semipermeable
perform
biological
geometries
to
role
processes,
cellulose
nitrate.
materials,
mainly
either symmetric or asymmetric, and their
124
From the point of view of 3D-packaging,
physical strength can be improved with the
cellulose is a recyclable, biodegradable, and
use of support layers. Cellulosic materials are
intrinsically highly hydrophilic and therefore
2. Objectives
ideal for water-based membrane processes.
Although synthetic polymers have taken over
New types of bio-based materials were tested
some membrane applications, it is believed
in different packaging applications with the
that novel cellulose materials and advanced
aim of improving traditional fibre products. The
processing technologies will open up new
main objectives were:
possibilities for cellulose, thus reclaiming some
markets from synthetic polymers.
• To develop multi-layered board packaging
structures, including layers made of possible
The pulp and paper industry is a large consumer
sidestreams such as xylan, GGM, TOFA or
of water, the quality of which varies widely, for
dissolved cellulose, with good grease barrier
example in terms of amount and type of solutes,
properties at high relative humidity to create
pH and temperature. As an example, selected
holistic usage of all materials in a mill/
properties of three waters from pulp mill UF
production site
applications are presented in Table 1. Membrane
life cycles are typically expected to be several
In 3D-mouldable packaging structures, the ob-
years, and the typical water processing cost is
jectives were:
less than 1 €/m3, a third of which is attributed
to membranes. Cost reduction is needed, as
• To improve of the formability of paper webs
increasing requirements for process water
to a qualitatively new level and develop fibre
recycling are expected in the future. Typical
web based materials for producing deep 3D
water consumption of a pulp mill is currently
shapes (2-3 cm) using industrially feasible
around 20-30 m3 per tonne of pulp. With more
advanced membrane technology this could be
technology
• To demonstrate the convertability of the
reduced to less than 10 m3 / tonne. Filtration
developed paper-based materials in existing
performance, stability in harsh conditions,
and emerging forming processes
long life span, and low price are key factors
• To increase knowledge of the role of
for membranes used in the pulp and paper
mechanical properties and process
industry.
parameters in the formability of paper webs
In filter development, the objective was:
• To improve the flux, retention, and/
or prolong the lifespan of membranes,
especially those used in pulp and paper
industry water systems.
Table 1. Typical examples of pulp mill ultrafiltration waters (pH, temperature and chemical oxygen demand
(COD) – commonly used as an indirect measure of organic compounds).
Water
pH
Temperature
COD
White water from the pulp drying machine
4–5
50 °C
500-650 mg/l
EOP filtrate from the bleaching plant
9 – 10
60 °C
2000-5000 mg/l
13
70 °C
> 100000 mg/l
Press washer filtrate after chemical cooking
125
Figure 1 shows a schematic of the barrier
development approach. In the barrier research,
Three product applications were selected for
each of the six material groups developed
initial piloting and demonstration: 1) grease
their products individually (Figure 1: Synthesis).
barrier in multilayer board packaging structures,
Studies
and 2) 3D-mouldable webs and 3) filters.
coating assisted in the evaluation of the film
When the results for the different materials
formation properties and application recipe
developed in the first FuBio programme for
of the materials (Figure 1: Self-standing films,
similar
the
Spin coating). All materials were applied on a
importance of centralized testing environments
selected base board and the resulting barrier
and measurements became clear. Therefore,
properties were tested (Figure 1: Laboratory
in the present programme centralized testing
coating, Pilot coating). After each coating
platforms were designed.
application round (several laboratory rounds
applications
were
compared,
on
self-standing
films
and
spin
and a pilot trial) feedback was given to the
In
packaging
barrier
research,
material
material development groups and improvement
a
targets were agreed (e.g. moving from solvent-
grease barrier by means of dispersion coating,
based system towards water dispersion, aiming
improving the mouldability of conventional
for a less tacky product, etc.). After two years,
fibre webs, and demonstrating and piloting the
the industrial tutors selected the three most
developed materials.
promising derivatives for an additional pilot
development
was
aimed
at
achieving
• Comparison between
samples that spread well
• Clear effect of substrate
and barrier sample
chemistry
Synthesis
Self-standing films
Pilot coating
Extrusion
Spin coating
Laboratory coating
Converting
Figure 1. Barrier research approach.
126
scale trial. After pilot coating the biobarrier-
formability was improved via two approaches:
coated webs were extrusion coated and further
1) increasing the extensibility potential of fibres
converted into tray form, representing the final
and paper, and 2) subjecting swelled pulp fibres
product (Figure 1: Extrusion, Converting).
to extremely high pressure loads. Table 2 shows
the research approach.
As part of the dispersion barrier development,
additional studies with dual-polymer systems
In filter development, the used test waters
with and without high aspect ratio plate-
were kept as constant as possible throughout
like pigment addition were also conducted in
the project and fibres and new technologies
order to increase the grease resistance and
were studied with the aim of producing
convertability of paperboard. The effect of
materials applicable in reactive and active
the base substrate on flexible packaging was
filter and membrane applications. The work
evaluated with special attention to the fibre
included membrane and membrane component
composition. The effect of fibre composition on
development and functionalization as well
convertability was studied by preparing a novel
as study of membrane properties. The main
papermaking fibre with cellulose-rich fibre
approaches
surfaces by enzymatic hemicellulose removal.
included casting of membranes using ionic liquid
to
membrane
development
(IL) and preparation of nano- and micro-fibrous
In the 3D-mouldable web research task,
materials for layered structures using coatings
various approaches were taken to improve
of dicarboxylic acid cellulose (DCC) nanofibres
the formability of paper-based materials. The
and electrospun micron and sub-micron fibres.
Table 2. Mouldable web research approach.
127
4. Results
area with respect to 3a) grease resistance and
water vapour barrier or 3b) oxygen and water
4.1 Improving grease resistance in
multilayered board packaging structures
vapour barrier.
Regarding
the
cellulose-copolymer
blends
In the barrier research, new coating materials
(CePE), grease resistance of over 65 days
for achieving grease resistance of paperboard
was obtained with a dissolved cellulose/
in packaging applications were developed.
poly(ethylene-co-acrylic acid) blend with a
One aim was to obtain the coating materials
95/5 polymer/polymer ratio. After dispersion
as water-based dispersions. Six different types
coating, the best OTR achieved was 130 cc/
of bio-based derivatives were developed and
(m2d bar); however after PE extrusion OTR the
tested during the project. These were modified
value was as low as 2 cc/(m2d bar). The WVTR
GGM (Åbo Akademi University), modified xylan
target was also achieved. In this group, the
(VTT), TOFA esters and TOFA alkyd acrylates
blending capability of commercial co-polymers
(University of Helsinki), dialdehyde cellulose
with alkaline aqueous cellulose solution was
alginates (University of Oulu) and cellulose-
studied and the mixing procedure and blend
copolymer blends (Aalto University). Additionally,
compositions developed. This was done in order
the barrier coatings were up-scaled from lab
to obtain the best morphology of the solutions/
to pilot scale and the multi-layer paperboard
suspensions for the coating trials.
packaging structures with good grease barrier
properties were demonstrated. More than 60
TOFA-based
derivatives were tested during the project.
synthesized and applied on paperboard and
hybrid
latexes
(HL)
were
Centralized coating tests were performed at
water and grease barrier properties were
VTT facilities (Figure 2) and pilot coated samples
analysed. Good water and water vapour barrier
were further sent to TUT for extrusion coating
properties were achieved, whereas the grease
and LUT for conversion into tray form.
barrier was moderate. Oxygen barrier property
was improved when talc or cellulose was used
Sample characterisation was also conducted
as filler. The materials were also heat-sealable.
in a centralized testing environment, including
However, some process scale-up issues (e.g.
grease, water vapour transmission (WVTR) and
adhesion problems) remained unresolved.
oxygen barrier (OTR) measurements.
The
128
xylan
derivatives
–
in
particular
When considering the grease barrier, the most
hydroxypropylated xylan (HPX) dispersions
promising coatings are cellulose-copolymer
– could be coated as such, cross-linked,
blends (CePE) and hydroxypropylated xylan
plasticized and filled with talc or nanoclay and
coatings. Figure 3 shows the results for the
showed good grease barrier properties in all
best candidate of these two (CePE and xylan)
cases. The barrier-enhancing fillers concept
as well as TOFA hybrid latex (HL) derivative
was demonstrated and WVTR of 46 g/(m2d)
families as normalized to 20 µm thickness. In
and OTR of 72 cc/(m2d bar) were achieved.
grease resistance measurements our target
In addition, the concept of low DS combined
was to attain extended resistance, i.e. high
with external plasticization, enabling a bio
values when measured in days (y-axis) as
content of up to 90%, was tested successfully.
well as low water vapour and oxygen transfer
The colour of the coating material colour was
rates (WVTR and OTR, respectively). The blue
white and remained stable during drying and
circle represents the combined target value
converting. Heat sealability was achieved, and
Figure 2. Pilot trial equipment at VTT.
a)
b)
Figure 3. Best barrier properties of the three most promising derivatives normalized at 20 µm thicknesses,
measured at 23 oC, 50%RH. The targeted area in Figure a) is in the top left corner and in Figure b) in the
bottom left corner.
PE extrusion coating was possible leading to
and multi-layer paperboard structures with
OTR values below 10 cc/(m2d bar). Die-cutting
several beneficial characteristics, especially
and press-forming into trays was successful.
grease barrier properties, were produced. All
of the derivatives require further optimization
In conclusion, several potential barrier dispersion
according to the target end use, but can be
coatings were developed and demonstrated
readily utilized at the industrial scale.
129
Improving grease resistance of starch-based
4): a) mechanical treatment of fibres to reduce
coatings
their axial stiffness, create microcompressions
When synthetic polymer was added to
and dislocations (steps 2 & 3); b) improvement
modified
(dual-
of inter-fibre bonding by spray application of
polymer system) at optimized amounts,
polymers (step 4) c) structural modification
efficient grease resistance was achieved. The
of the fibre network by in-plane compaction
addition of synthetic polymer to starch-based
treatment and unrestrained drying of the paper
coatings improved the elastic properties and
to allow free shrinkage (steps 5 & 6). Used in
plasticity and, subsequently, the mechanical
combination, these stages could achieve paper
convertability of the product. Addition of plate-
elongation of 15…30%. In addition to these
like like pigment to the renewable dispersion
treatments, the forming conditions (mainly
coating increased the grease resistance of
temperature and moisture content of paper) that
the non-converted blanks, whereas micro-
affect the softening of the polymers (cellulose,
scale cracks in the barrier were frequently
hemicelluloses, added polymers) could improve
observed after tray conversion, resulting in
the extensibility by 2–4 percentage points. It
poor grease resistance.
was found that paper at a moisture content of
starch-based
dispersion
8-11% can soften at 80 °C, but further increases
in temperature or moisture decrease formability.
Effect of hemicellulose removal on
The combined approach for the improvement of
convertability
The
effect
of
fibre
composition
on
formability is shown in Figure 4.
convertability was studied by preparing a
novel papermaking fibre with cellulose-rich
The
fibre surfaces by enzymatic hemicellulose
polymers was tested (starch, xyloglucan,
removal. Xylanase treatment of refined never-
hydroxypropylcellulose, CMC, gelatin, agar).
dried bleached birch kraft pulp demonstrated
Spray addition of these biochemicals was found
selective
the
to increase both strength and elongation. The
outermost fibre layers, reducing 14.2 wt% of
most interesting chemicals were agar and
the total amount of xylan in the studied pulp.
gelatin. For example, gelatin improved the
The mechanical properties of paperboard at
extensibility and tensile strength of unrestrained
180 g/m2 grammage were mainly preserved
and restrained dried paper. A 4% gelatin addition
despite a 14.2 wt% reduction in xylan content.
improved the tensile strength from ca. 50 Nm/g
Press-forming of the produced materials
to ca. 80 Nm/g, and extensibility from ca. 9%
revealed differences related to the end
to 13% for unrestrained dried paper. However,
moisture content of the produced paperboard
besides strengthening fibre bonding, chemical
(i.e. drying severity), fibre composition (i.e.
addition also increased drying shrinkage.
hydrolysis
of
xylan
from
application
of
several
natural
hemicellulose content), and press-forming
parameters. Consequently, the suitability of
Papers prepared using the combined approach
the paperboard could be optimized for flexible
(as shown in Figure 4, excluding the compaction
packaging
stage) were used to produce three sets of demo
by
tailoring
the
carbohydrate
composition of the base substrate.
materials. The test results clearly demonstrated
that different forming processes have different
4.2 Improving formability of paper-based
materials
formability requirements. One key difference
between the processes is whether the paper
blank is allowed to slide into the mould (sliding
130
The approach used for improved formability of
blank) or whether it is strained into the mould
the fibre web included three major stages (Figure
(fixed blank). In the deep-drawing process
Figure 4. Combined approach for improvement of formability.
Figure 5. Classification of the basic forming methods tested and examples of shapes obtained. The hot
pressing mould is a VTT Design.
the paper is allowed to slide and the depth of
was obtained at a polymer dosage of 8%.
the shape is almost unlimited, although the
In-plane compaction further increased the
appearance worsens with increased depth.
extensibility up to 35% in the machine direction.
The basic process types tested in the project
Gelatin effectively improved the extensibility
are classified in Figure 5. Detailed photos of
and tensile strength of the paper and readily
samples made in fixed blank processes are
adsorbed on the fibres. For enhanced effects, a
shown in Figures 6-8.
combination of several chemicals can be used.
These treatments are compatible with current
Maximum paper extensibility of around 21%
papermaking environments and can be used for
131
Figure 6. Tray-like shapes (underside and top side) obtained by a hot pressing process developed by the
Moldable Web project at VTT. The shape depth is around 16 mm.
Figure 7. Double-curved structure produced by
hydroforming. Around 20% extensibility is required
for this formation. (Hydroforming performed by the
Royal Institute of Technology (KTH), Sweden.)
1)
2)
Figure 8. Tray-like shape air-formed by PACCOR
(Coveris). Maximum shape depth ~25 mm.
3)
4)
Figure 9. Schematic approach for the improvement of mouldability of cellulose (ÅA): 1) Starting material:
softwood dissolving pulp; 2) Swelling of cellulose in DMAc-LiCl; 3) Forging the swelled cellulose at 70MPa
pressure; 4) The resulting cup-like form, height ca. 50 mm.
132
the production of food packaging material. The
ture of the obtained material was unique and
convertability of the produced paper materials
the properties of the produced membranes var-
was demonstrated in all main forming process
ied according to the process parameters, such
types.
as coagulation bath temperature and used additives. In lab-scale testing, the prepared mem-
Preparation of three-dimensional cellulose
branes were compared with one of the best
objects from fibres previously swelled in
commercial RC70PP membranes.
DMAc/LiCl solvent system
In this approach, the aim was to take advan-
One membrane sample was produced for in-
tage of the modifications in intermolecular in-
dustrial trials for comparison with commer-
teractions that swelling treatment induces in
cial references. The sample was pure cellulose
cellulose in order to be able to subject the cel-
(8 wt-%) without any additives or any surface
lulose to moulding and high pressure. Cellulose
functionalization supported by PET nonwo-
pulp was swelled with DMAc/LiCl solvent sys-
vens. Industrial trials were carried out by Valmet
tem, washed and dried before further process-
Technologies at the Metsä Fibre Rauma mills
ing. In addition, acrylated epoxidized soybean
using a CR250/2 unit (effluents listed in Table
oil was incorporated into the swollen fibres to
3). Retentions of the studied sample were simi-
improve mouldability. The formability of these
lar or slightly lower than the commercial refer-
treated cellulose samples was then evaluated.
ences (see white water example in Table 3), and
in general the demo sample showed very sta-
This approach is unique in that the core treat-
ble, but somewhat lower flux in all tested efflu-
ment involves the swelling of the dissolving
ents compared to the commercial membranes.
pulp in non-aqueous salt solution to disrupt the
inter- and intramolecular hydrogen bonding
The results obtained are very promising, as
and decrease the crystallinity of the cellulose,
there are currently no commercial cellulose
with subsequent forging under high pressure
membranes fabricated directly from cellulose.
to create a dimensionally stable shape. Swell-
The membrane preparation process however
ing of cellulose in non-aqueous salt solution
requires further development in order to opti-
with consequent forging may be used for the
mise the membrane properties for specific end
production of three-dimensional translucent
uses, to enable the production of larger mem-
shapes from cellulose.
brane pieces for flat membranes, and to transfer the technology to hollow fibre (HF) mem-
4.3 Main results for filter materials
brane production.
IL casting
Functional IL-cast membrane
Casting based on phase inversion by immersion
IL casting was also used to create temperature-
precipitation typically produces an asymmetric
responsive membrane in cooperation with LUT
membrane structure with a thin, tighter skin lay-
and VTT. VTT’s allylated cellulose was cast at
er for good separation on one side and an open
LUT and subsequently grafted with poly(N-iso-
pore structure bulk layer providing good flux.
propylacrylamide) (PNIPAAm) at VTT. A non-
Such materials are typical in UF filtration appli-
grafted reference and the PNIPAAm grafted
cations. LUT’s casted membranes were based
demo material were tested at the lab scale.
on commercial cellulose dissolved into IL liquid.
Stimuli-responsive behaviour of the grafted
The solution was cast and the resulting wet film
membrane was observed in pure water flux
was soaked in a non-solvent bath. The struc-
testing as well as anti-fouling and easy-clean-
133
a)
b)
c)
Figure 10. a) Pure water flux at different temperatures; and b) at different stages of wood hydrolyzate
filtration; and c) appearance of non-grafted and PNIPAM grafted allylated cellulose membrane. In (c) nongrafted sample on left, grafted on right.
Table 3. Analyzed compounds in the feed and the permeate samples of white water using the LUT demo
sample and commercial RC 30 kDa membrane.
Sample
COD total mg/l
COD
soluble
mg/l
pH
Conductivity
mS/m
Charge
µekv/l
TSS GF/A
mg/l
Turbidity
NTU
White water
feed
610
520
4.5
230
-40
167
128
LUT demo
sample
470
460
4.8
220
-32
0
0.4
Reduction
23%
12%
4%
20%
100%
100%
RC 30 kDa
500
490
220
-15
0
0.3
Reduction
18%
6%
4%
63%
100%
100%
4.8
ing properties during wood hydrolyzate filtra-
on top of a commercial support material using
tion, see Figure 10. The cycle was repeated
DCC-nanofibrils (see Figure 11). The properties
twice and the properties of the grafted mem-
of the produced membranes depended on the
brane restored fully after each cycle.
various process parameters, such as the layer
thickness and used cross-linking agent.
DCC nanofibre coating
134
Layered structures are characteristic of fibrous
These cellulose-based membranes are best
materials. Whereas an asymmetric pore size
suited to neutral conditions with a pH range of
distribution is obtained inherently in casting,
1-11, preferably 5-9. The membranes can puri-
a similar effect can be obtained by combining
fy clear water from feed solutions where the
layers of different pore size. Support materi-
largest contaminant particles have been re-
al layers provide mechanical strength without
moved and the temperature is below 70˚C. The
significantly affecting flux, while layer(s) with
functionality of the fabricated membranes was
smaller fibres and pore sizes provide effective
demonstrated with real industrial process wa-
depth filtration. University of Oulu prepared a
ter with a high level of purification achieved
new type of membrane barrier layer structure
with paper machine disc filter fractions (cloudy
a)
b)
Figure 11. DCC barrier layer (a) surface structure and (b) cross-sectional structure.
and clear filtrate). The filtration efficiency in
materials was demonstrated in all main forming
terms of fouling, flux and purification degree
process types. Here the exploitation potential
was as good as the commercial reference
of the results depends on the raw material pric-
UH030 when CaCl2 was used as a cross-linking
es of addition chemicals and costs for new unit
agent in membrane preparation.
operations. The development of new filter materials shows promising results, however this
The results obtained with this demo materi-
area needs a lot of research before industrial
al were very promising. The vacuum filtration
products can be talked about.
method of producing samples proved effective
at the laboratory scale, indicating that efficient
This work will have it’s largest impact on im-
production of larger membranes by roll-to-roll
proving conventional fibre products through
coating can be achieved.
increased knowledge among researchers and
industry in the areas of biobarriers, mouldable
results
packaging and filter.
6. Networking
Initial process piloting and material prototype
production tasks focused on improving con-
Several research partners were involved this
ventional fibre products. Whilst different types
study. In addition, industry partners actively
of biobarriers were successfully prepared and
participated in steering and guiding the work
coated as water dispersions on precoated base
and in conducting measurements and trials,
board many process and product issues still
see Table 4. Partner organizations and their re-
need to be solved before any of the materials
search roles.
can be taken to products. In the case of 3Dmouldable packaging, on the other hand, the
studied treatments are compatible with current
papermaking environments and can be used
for the production of food packaging materials.
Also the convertability of the produced paper
135
136
Aalto University
• Polymer Technology (P)
• Forest Products Technology (FP)
(P) Blending capability of commercial co-polymers with alkaline
aqueous cellulose solution, mixing procedure to obtain best
morphology in the solutions and to function well as barrier coatings.
(FP) Preparation of model surfaces, analysis of model surfaces and
spin coating. Investigation of the effect of different polysaccharides
and their properties on web mouldability. Membrane
functionalization by click chemistry.
Kemira
Assisted partners with dispersion knowledge, Industrial tutor.
Technology
• Packaging Technology (PT)
• Fiber and Paper (FP)
• Separation Technology (ST)
(PT) Production and collection of commercial samples for the
coating testing platform.
(FP) Studies on coating hold-out, infiltration with an aim to identify
the effect of substrate properties on paper-coating interaction.
(ST) Preparation of Cellulose Membranes.
Metsä Board
Industrial tutor
Metsä Fibre
Industrial tutor
Stora Enso
Task 2 Coordinator, study on microwavable packaging materials,
barrier measurements, converting trials.
Tampere University of Technology
• Paper Converting and Packaging
Technology
Provided the dissolved cellulose for Aalto Polymer Technology
Extrusion coatings, measurement of barrier properties
• Organic Chemistry (OC)
• Polymer Chemistry (PC)
• Food and Environmental Sciences
(FES)
(OC) prepared materials with good grease barrier properties for
coating experiments using dissolving pulp as starting material.
(PC) Preparation of alkyd-acrylate copolymers. Structural
characterization of products.
(FES) studies of free films, mechanical and barrier properties.
University of Oulu
• Fibre and Particle Engineering (FPE)
• Organic chemistry (OC)
(FPE) Mechanical activation, production of micronized cellulose
and application testing. Membrane structures based on DAC/DCC
microfibers.
(OC) Chemical derivatization and functionalization of fibre material,
production of new modified carbohydrates.
UPM-Kymmene
Task 1 Coordinator
Valmet
Task 3 Coordinator, industrial testing of developed membrane
material.
VTT
WP leader. Chemical modification of xylan, development of TOFAbased alkyds, model surface studies, barrier testing, laboratory
and pilot coating. Chemical modification of pulp, grafting of
thermoplastic polymers and impregnation of webs with polymers.
Verification of the testing platform for formability. Functionalization
of fibres for membranes and commercial cellulose-based
membranes, especially stimuli-responsive materials. Electrospun
membranes. Membrane testing, lab-scale preparation of (demo)
membrane materials.
• Wood and paper chemistry (WPC)
• Fibre and cellulose technology (FCT)
(WPC) Chemical modification of GGM, optical method for grease
barrier determination.
(FCT) Preparation of cellulose 3D objects using physicochemical
pretreatments of pulp fibres in combination with mechanical
treatment or forging.
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Zeng, X., Vishtal, A., Retulainen, E, Sivonen,
E. and Fu S. The Elongation of Paper – How fibres should be deformed to make paper extensible?, BioRes, 2013, 8, 1, 472-486.
138
The main objective of FuBio is to establish, in Finland, globally competitive
knowledge platforms within the field of wood biorefinery R&D for the
renewal of the forest industry and creation of new business.
FuBio is focused on development of novel value chains, in which wood is
refined into especially materials and chemicals.
www.fibic.fi

Future Biorefinery Joint Research 2

Transcription

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