Cellulose activation

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FuBio Seminar 27.8.2013

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Cellulose activation

  1. 1. 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
  2. 2. 2 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
  3. 3. 3 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. 4. 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
  5. 5. 5 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
  6. 6. 6 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
  7. 7. 7 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
  8. 8. 8 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
  9. 9. 9 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
  10. 10. 10 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
  11. 11. 11 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
  12. 12. 12 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
  13. 13. 13 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 Nomechanical treatment Acid vrs. enzymatic hydrolysis Effect of enzyme dosage
  14. 14. 14 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
  15. 15. 15 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 FibresPulp
  16. 16. 16 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
  17. 17. 17 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
  18. 18. 18 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
  19. 19. 19 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
  20. 20. 20 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

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