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FuBio Seminar 27.8.2013
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1
Cellulose activation
Stina Grönqvist (VTT), Thad Maloney (Aalto),
Taina Kamppuri (TUT), Marianna Vehviläinen (TUT),
Terhi K. Hakala (VTT), Tiina Liitiä (VTT),
Tuomas Hänninen (VTT), Anna Suurnäkki (VTT)
Finnish Bioeconomy Cluster FIBIC Oy
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Cellulose activation
What and how:
Opening of pores and altering of fibril aggregates and highly ordered regions in cellulose fibres by:
Mechanical treatments
Degrading treatments
Swelling treatments
Why:
To enhance the accessibility and reactivity of cellulose to chemicals (solvents and reagents)
Dependent on the structure and morphology of the cellulose fibres and solvent or reagent used
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Motivation
Currently, the strategic target for the European forest industry is to find new viable applications for wood fibres.
The industrial interest is focused on novel added-value products based on regenerated fibres.
This is mainly due to the promising market trends especially in the textile industry combined with the environmental considerations related to currently used fibre raw materials, e.g. cotton.
Current regenerated fibres produced by e.g. viscose and Lyocell processes involve the use of harsh and toxic chemicals.
Fubio cellulose aims to develop novel sustainable, both non-aqueous and aqueous based solvent systems for dissolving pulps
Finnish Bioeconomy Cluster FIBIC Oy 29.8.2013
4
Dissolution Dissolving grade pulp
Pre-treatment: mech. + enz. treatments
Regenerated fibres
Clothes
Hygiene products,
wipes
FuBio Cellulose
From cellulose to textiles
The process development of novel sustainable solvent systems for cellulose is connected with the opening up of the fibre structure
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Dissolving grade pulps
Finnish Bioeconomy Cluster FIBIC Oy 29.8.2013
Produced either by sulphite or prehydrolysis kraft process a high cellulose content and only traces of hemicelluloses and lignin
Dissolving grade pulps used for: production of cellulose derivatives regenerated cellulose
Requirements: good accesibility and reactivity of cellulose
Challenges:
The removal of the non-cellulosic compounds in pulping and bleaching cause, the cellulose fibrils to aggregate and form tight structures in drying
decreased fibre reactivity the lost conformability and swelling capacity cannot be recovered by rewetting the fibres
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Cellulose fibres
Finnish Bioeconomy Cluster FIBIC Oy 29.8.2013
Egal Mlle Magali (2006): Structure and properties of cellulose/NaOH aqueous solutions, gels and regenerated objects. Ecole Doctorale 364: Sciences Fondamentales et Appliquées, Ecole des mines de Paris, France, p.30.
Simplifying :
Wood is a complex natural composite built up of fibres that are glued together by lignin
fibres consist of fibrils that are held together by lignin and hemicellulose.
fibrils are built up of bundles of microfibrils
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Schematics
of cellulose
microfibril
behavior during
different
processing
steps
Finnish Bioeconomy Cluster FIBIC Oy 29.8.2013
Pönni et al (2013): Accessibility of cellulose: Structural changes and their reversibility in aqueous media, Carbohydrate Polymers. Volume 93, Issue 2 2013 424 - 429
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Mechanical treatment
Enzyme treatment
Dope Fibres
State-of-the-art Biocelsol process
Scale: 500 g Mechanical shredding by Baker Perkins, 5 h, 20 % Enzyme treatment: commercial enzyme, pH 5, 3h, 5 %
Pulp
Disintegrated pulp Mechanically treated pulp (5h)
No major changes in the
visual appearance of fibres due to 5 h mechanical shredding by the Baker Perkins machine
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What does the state-of-the-art treatment do?
Finnish Bioeconomy Cluster FIBIC Oy 29.8.2013
Mech. treatment
Baker Perkins
(0- 5h)
Enzymatic
(2 dosages) vrs. acid hydrolysis
Dissolution of samples in NaOH/ZnO
Pulp
Analyses: dissolved sugars, pulp viscosity, molar mass distribution, pore size
distribution, WRV, solubility
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Enzyme aided modification of cellulose
Finnish Bioeconomy Cluster FIBIC Oy 29.8.2013
Kvarnlöf 1997: Activation of dissolving pulps prior to viscose preparation. Dissertation. Karlstad University.
Aim: To drop the pulp viscosity to a level where dissolution of cellulose in selected solvent system is possible
Due to the compact structure of cellulose the accessibility to chemicals and enzymes is restricted mechanical treatment needed
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Finnish Bioeconomy Cluster FIBIC Oy 29.8.2013
Dyes:
Yellow; larger particles and higher affinity to cellulose
Blue; smaller in size, stains all sites that are too small for the yellow dye
More yellow -> more open structure
Shredding time min
micropore volume
g/g
total pore volume
g/g
Accessible surface area
m2/g
0 0.42 0.53 9
30 0.43 0.75 28
60 0.44 0.78 29
150 0.47 0.82 30
300 0.48 0.91 37
Simons staining Solute exclusion approach
Effect of shredding with Baker Perkins on fiber
structure
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Effects of shredding on the following
enzymatic hydrolysis step
Finnish Bioeconomy Cluster FIBIC Oy 29.8.2013
• Shredding (0-300 min) as indicated in the figure • Enzyme treatment: 2h, 50°C, pH 5
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Porosity development by hydrolysis
Finnish Bioeconomy Cluster FIBIC Oy 29.8.2013
Shredding time min
micropore volume
g/g
total pore volume
g/g
Accessible surface area
m2/g
Disintegrated pulp 0.42 0.53 9
Shredded 5 hours 0.48 0.91 37
Shredded 5h + 2h E (0.25 mg/g)
0.61 1.05 38
Shredded 5h + 2h E (1 mg/g) 0.61 1.17 48
Treatment micropore volume
g/g
total pore volume
g/g
Accessible surface area
m2/g
Disintegrated pulp 0.42 0.53 9
Acid hydrolysis (viscosity ~250 ml/g) 0.36 0.43 6
Enzymatic hydrolysis (viscosity ~250 ml/g) 0.62 0.86 21
No
mec
ha
nic
al
tr
eatm
ent
Acid vrs. enzymatic hydrolysis
Effect of enzyme dosage
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Effect of pre-treatments on solubility
29.8.2013
300 min
60 min
30 min
150 min
Pulps shredded by Baker Perkins and then treated enzymatically (1 mg/g) for 2h.
Cellulose content in the solutions was 5.5 wt%.
Shredding time
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Development of novel sustainable aqueous
based dissolution systems
Finnish Bioeconomy Cluster FIBIC Oy 29.8.2013
The mechanical treatment should: Modify accessibility of cellulose for enzymatic (and/or chemical modification) Be techno-economically feasible
The enzymatic treatment should:
Drop pulp viscosity, without formation of low molecular weight material, low polydispercity of Mw-distribution
As a result of the combined mechanical and enzymatic treatments:
Cellulose should be soluble in selected system (here in NaOH/ZnO) and result in a clear solution without undissolved particles
The properties of the regenerated fibres should be on targeted level
Mechanical treatment
Enzyme treatment
Dope Fibres Pulp
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Screening of new enzymes
accepted discarded discarded discarded
Shredding Enzymatic treatment
Pulp Dissolution
into NaOH/ZnO
Microscopy images
Falling ball viscosity and
alfa
If soluble
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Screening of potential mechanical treatments
Testing of various mechanical equipment
Equipment selected based on expected capability to cause internal (and moderate external) fibrillation
Conditions for the mechanical treatment selected based on prior to art knowledge
Finnish Bioeconomy Cluster FIBIC Oy 29.8.2013
Sprout Waldron disc refiner, Pearl mill PFI mill
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Screening of various ways to combine the
mechanical and enzymatic processing steps
Pulp than can be dissolved in selected
solvent and results in regenerated fibres with
target properties
Finnish Bioeconomy Cluster FIBIC Oy 29.8.2013
Pulp
Enzymatic treatment
Mechanical treatment
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Conclusions
The process development of novel sustainable solvent systems for cellulose is connected with the opening up of the fibre structure
Apparently, it is necessary to break internal bonds within the fibre wall so that fibres swell and pores expand.
In the studied system:
Opening of the fibre matrix due to mechanical treatment seems to proceed in steps, it seems that after a certain amount of stress some structures are broken down or collapsed, resulting in further opening of the matrix.
The surface area available to an enzyme increased from 9 to 37 m2/g in 5 hours of shedding and was further increased substantially by the action of the enzyme.
There seems to be limited amount of accessible sites with adequate pore size available in the pulp for enzyme catalysis
Increased porosity results in better solubility of the cellulose.
The work carried out to develop novel sustainable aqueous based dissolution systems for dissolving pulps has resulted in very promising results.
Finnish Bioeconomy Cluster FIBIC Oy 29.8.2013
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Acknowledgements
The work has been partially funded by the Finnish Bioeconomy Cluster (FIBIC) through the Future Biorefinery (FuBio) programme.
The technical assistance of Maija Järventausta, Leena Nolvi, Mariitta Svanberg and Nina Vihersola is gratefully acknowledged.
Finnish Bioeconomy Cluster FIBIC Oy 29.8.2013