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Lignin complexity: fundamental and applied issues

Lignin complexity: fundamental and applied issues. Göran Gellerstedt. Content. The lignin structure in wood Lignin chemistry in pulping Technical lignins. Content. The lignin structure in wood Lignin chemistry in pulping Technical lignins. Milled Wood Lignin.

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Lignin complexity: fundamental and applied issues

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  1. Lignin complexity: fundamental and applied issues Göran Gellerstedt

  2. Content • The lignin structure in wood • Lignin chemistry in pulping • Technical lignins

  3. Content • The lignin structure in wood • Lignin chemistry in pulping • Technical lignins

  4. Milled Wood Lignin Spruce: C9H8.62O2.48(OCH3)0.94 Phenolic OH: 20-30% Birch: C9H8.59O2.86(OCH3)1.52 Phenolic OH: Ref., Adler, 1977

  5. Monomer yield on thioacidolysis(theoretical: ~4700-5500 mmol/g)

  6. Mechano-chemical cleavage of b-O-4 structures in milling

  7. SEC of thioacidolysis products from spruce, eucalyptus and birch wood

  8. Dissolution of wood/pulp fibres by the use of enzyme • Endoglucanase • (Novozyme 476) • Action of urea • - Breaks down the crystallinity of the cellulose by • forming hydrogen bonds between the microfibrils • Dissolves any material containing > ~50% lignin • Removes enzyme contamination from the fibres • Action of alkaline borate solution • - Dissolves all remaining components

  9. Types of LCC isolated from spruce wood meal

  10. SEC of acetylated thioacidolysis products from spruce LCCs Dimer Monomer Xylan-rich LCC (40% lignin on wood) Glucomannan-rich LCC (48% lignin on wood) Response Wood

  11. Suggested lignin structures in spruce wood Linear xylan-lignin Branched glucomannan-lignin

  12. S/G ratios in hardwoods

  13. G-units/S-units in white birch wood Ref. Saka and Goring, 1988

  14. The lignin structure in hardwoods … contains a high proportion of S-units which results in a high percentage of linear lignin – unevenly distributed

  15. MS-identification of lignin fragment from E. globulus lignin Evtuguin et al, 2003

  16. Lignin in annual plants

  17. Content • The lignin structure in wood • Lignin chemistry in pulping • Technical lignins

  18. Dissolution of lignin and carbohydrates in kraft pulping Residual lignin; removed by bleaching

  19. Degree of delignification for different wood species

  20. Kraft pulping of birch and E. globulus respectively to similar kappa numbers E. globulus Birch

  21. b-O-4 structures in wood and pulp based on thioacidolysis (birch and eucalyptus) Degradation product, mmol/g of lignin Klason lignin, %: 16.6 0.6 18.3 0.9

  22. Size exclusion chromatography (SEC) of lignin degradation products(no ”residual lignin” present in wood) • Methodology • Thioacidolysis of wood/pulp • Acetylation • SEC in tetrahydrofuran

  23. Suggested mode of formation of radical coupling products in kraft pulping

  24. Principles in the steam explosion process(Conditions: ~190-240 oC, 1-5 min)

  25. Chemical composition before and after steam explosion Spruce samples Birch samples Substantial removal of hemicelluloses and extractives: SO2SE > TwoSE > OneSE

  26. Lignin isolation yield (hardwoods) Aspen samples Birch samples SO2SE > OneSE (missing lignin from aspen  highly soluble lignin)

  27. SEC of acetylated lignin from steam exploded aspen wood

  28. Degradability by thioacidolysis/SEC analysis Spruce Condensation  less degradability

  29. Degradability by thioacidolysis/SEC analysis, SE aspen monomers SO2SE SE

  30. Steam explosion chemistry

  31. Content • The lignin structure in wood • Lignin chemistry in pulping • Technical lignins

  32. Biomass tree showing the main chemical outlets Ref. Rintekno oy, 1984

  33. Highest-value lignin uses to show greatest future rise (W. Glasser) As structure of lignin yields to advances in analytical techniques, new markets are projected in adhesives, foams, films, coatings and plastics Ref: C&EN 1984

  34. The Biorefinery Concept • Production of large volumes of ethanol will be necessary in a short term • New separation process(es) for lignocellulosics required • New chemistry based on carbohydrates will be developed • Lignin for fuel – and for chemicals • On a longer term, gasification of biomass to syngas (biodiesel) will be developed

  35. Indicative targets for the share of biofuel in the EU • 2005: 2% (not achieved) • 2010: 5.75% (will probably not be achieved) ------------------- • 2007: New energy policy document setting a minimum requirement at 10% by 2020

  36. From biomass to liquid fuels • Biodiesel from oils and fat; rapeseed etc – esterification with methanol • Biochemical pathways to ethanol; 1) Sugar beet etc – sugar-fermentation 2) Starch crops – hydrolysis-sugar-fermentation 3) Lignocellulosics – separation-hydrolysis-sugar- fermentation; lignin as byproduct • Thermochemical pathways to biofuels; 1) lignocellulosics – pyrolysis-bio oil-biofuels 2) lignocellulosics – gasification-methanol/FT-fuels

  37. Feedstock sources • Forestry waste (forest residue, bark, wood chips, thinnings) • Agricultural residues (straw, stover, bagasse) • Energy crops (poplar, willow, switch grass) • Municipal waste (paper, packaging,..)

  38. Biomass composition

  39. The ideal separation of biomass

  40. … and the reality • Kraft and soda pulping • Sulfite pulping • Acid hydrolysis • Steam explosion • Organosolv pulping At present, none of these processes results in an efficient and cheap separation

  41. Elemental analysis

  42. Substance Groups in Kraft Black Liquors(kg/ton of pulp) Ref: Sjöström 1993

  43. Principle for manufacturing of lignin from kraft black liquor

  44. Solvent fractionation of softwood kraft lignin Ref: Kringstad et al

  45. Lignin fractionation • Material: Industrial black liquor of softwood (pine/spruce), birch and eucalypt respectively • Fractionation:Ultra-filtration, 5 kD and 15 kD to remove high molecular particles / carbohydrates • Lignin isolation:Precipitation with CO2 (pH 9), • Acidwashing with H2SO4 (pH 2.3), • Drying • Purification:Cation-exchange to remove traces of Me+ Permeate Retentate

  46. SEC of kraft lignins before/after fractionation eucalypt softwood

  47. SEC-data from fractionated (5 kDa) kraft lignins

  48. Thermal analysis of purified kraft lignins

  49. Even a small lignin withdrawal can be interesting … … converted to 16,000 tonnes of CF Lignin withdrawal of 10% yields 33,000 tonnes 650,000 tonnes of pulp …to support 160,000 cars with CF-composite (~40% replacement)

  50. Conclusions • All native lignins are heterogeneous biopolymers linked to polysaccharides • Alkaline or acidic processes result in both lignin degradation and re-polymerisation • The up-grading of technical lignins require purification steps • Several options exist for an increased lignin use

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