complexity: fundamental and applied issues Göran Gellerstedt
Content The lignin structure in wood chemistry in pulping Technical lignins
Content The lignin structure in wood chemistry in pulping Technical lignins
Milled Wood Spruce: C 9 H 8.62 2.48 (CH 3 ) 0.94 Phenolic H: 20-30% Birch: C 9 H 8.59 2.86 (CH 3 ) 1.52 Phenolic H: Linkage type β--4' α--4' β-5' 5-5' 4--5' β-1' β β' Dimer structure Arylglycerol-β-aryl ether Noncyclic benzyl aryl ether Phenylcoumaran Biphenyl Diaryl ether 1,2-Diaryl propane Pinoresinol/lignan type Percent of total linkages Softwood Hardwood 50 60 2-8 7 9-12 6 10-11 5 4 7 7 7 2 3 Ref., Adler, 1977
Monomer yield on thioacidolysis (theoretical: ~4700-5500 μmol/g) Sample Spruce wood Spruce wood (preswollen) Spruce MWL Spruce TMP (preswollen) Birch wood (preswollen) Birch MWL Aspen wood (preswollen) Aspen MWL Yield of the main monomer(s), μmol/g Klason lignin 1332 1682 (31%) 986 1498 672 (G) + 2318 (S) = 2990 (63%) 403 (G) + 809 (S) = 1212 866 (G) + 1942 (S) = 2808 (58%) 609 (G) + 863 (S) = 1472 Content of phenolic H, Number per 100 C9-units n.a. 10-13 20 14 7.6 n.a. 10 n.a. H H R R CH 3 H 3 C
Mechano-chemical cleavage of β--4 structures in milling H 3 C CH 2 H CH CHH L CH 2 H CH CHH L L CH 3 M. E. Δ L CH 3 + CH 3 -H +H CH 2 H CH 2 C L L CH 3 H CH 3
SEC of thioacidolysis products from spruce, eucalyptus and birch wood Absorbance 1.2 1 0.8 0.6 0.4 0.2 ligomers Trimers Dimers Monomers Spruce Eucalyptus/Birch 0 20 25 30 35 40 Time, min
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
Types of LCC isolated from spruce wood meal Type of -Carbohydrate Complex, LCC yield, % GalactoGlucoMannan - Glucan - GlucoMannan - Xylan - 8 4 48 40
SEC of acetylated thioacidolysis products from spruce LCCs Dimer Monomer Xylan-rich LCC (40% lignin on wood) Response Glucomannan-rich LCC (48% lignin on wood) Wood
Suggested lignin structures in spruce wood CH H H H Me H Me H H 3 C H H CH 3 H 3 C H H 3 C H H H CH 3 CH 3 H CH 3 H Me Linear xylan-lignin H Me Xylan H Me H Me Me H Branched glucomannan-lignin H 3 C H H H H CH 3 H H 3 C H H H H H 3 C CH 3 H H H CH 3 H CH 3 H 3 C CH 3 H 3 C CH 2 H H H 3 C H 3 C H Glucomannan H H H H H CH 3 H CH 3 H H CH 3 CH 3 CH 3 H H H H CH 3
S/G ratios in hardwoods Wood species S/G-ratio Method Reference Birch Birch E. globulus E.globulus E. grandis 3.8 3.7 5.3 4.8 3.6 Thioacidolysis Nitrobenzene Thioacidolysis Pyrolysis Pyrolysis Gellerstedt et al, 2007 Chen, 1992 Gellerstedt et al, 2007 Gutierrez et al, 2007 Gutierrez et al, 2007
G-units/S-units in white birch wood Morphological Differentiation Fibre, S2-layer Vessel, S2-layer Ray parenchyma, S-layer Middle lamella (fibre-fibre) Middle lamella (fibre-vessel) Middle lamella (fibre-ray) Middle lamella (ray-ray) Guaiacyl/Syringyl 12 : 88 88 : 12 49 : 51 91 : 9 80 : 20 100 : 0 88 : 12 Ref. Saka and Goring, 1988
The lignin structure in hardwoods contains a high proportion of S-units which results in a high percentage of linear lignin unevenly distributed
MS-identification of lignin fragment from E. globulus lignin CH 3 H CH 3 H H CH 3 H H 3 C H H 3 C H 3 C CH 3 H H H 3 C H H 3 C CH 3 H H CH 3 Evtuguin et al, 2003
in annual plants rigin content H:G:S Flax Sisal Wheat straw Rice straw 2.9 (+ 1.6) 10.8 (+ 3.0) 16.0 6.1 57:33:11 (pyrolysis) 1:20:79 (pyrolysis) 5:49:46 (thioacidolysis) 15:45:40 (thioacidolysis)
Content The lignin structure in wood chemistry in pulping Technical lignins
Dissolution of lignin and carbohydrates in kraft pulping Residual lignin; removed by bleaching
Degree of delignification for different wood species Pulp type Kappa No kappa Pine 28.0 24.6 Birch 16.5 4.0 E. globulus 15.9 5.7 Delign. degree 94.0 98.2 97.5
Kraft pulping of birch and E. globulus respectively to similar kappa numbers E. globulus Birch
β--4 structures in wood and pulp based on thioacidolysis (birch and eucalyptus) Degradation product, μmol/g of lignin 3000 2500 2000 1500 1000 G S 500 0 Birch B pulp Euc E pulp Klason lignin, %: 16.6 0.6 18.3 0.9
Size exclusion chromatography (SEC) of lignin degradation products (no residual lignin present in wood) Methodology Thioacidolysis of wood/pulp Acetylation SEC in tetrahydrofuran
Suggested mode of formation of radical coupling products in kraft pulping S S S S S S S S S S S S S S S S R H 3 C R CH 3 H 3 C H R H 3 C Δ S S S S S S S S CH 3 H 3 C H H R CH 3 H 3 C H CH 3 R CH 3 Low reactivity due to H-bonding
Principles in the steam explosion process (Conditions: ~190-240 o C, 1-5 min)
Chemical composition before and after steam explosion 100 80 60 40 20 0 Spruce samples Birch samples Wood S2SE nese TwoSE Wood S2SE nese Extractives (Ara)-xyl (Gal)-Gluman Glucan Substantial removal of hemicelluloses and extractives: S2SE > TwoSE > nese
isolation yield (hardwoods) 120 100 80 Residual 60 40 Extractable, NaH 20 0 Birch samples Aspen samples S2SE nese S2SE nese S2SE > nese (missing lignin from aspen highly soluble lignin)
SEC of acetylated lignin from steam exploded aspen wood
Degradability by thioacidolysis/sec analysis Spruce Condensation less degradability
Degradability by thioacidolysis/sec analysis, SE aspen monomers S2SE SE
Steam explosion chemistry H H H High temperature CH 3 H 3 C Stabilisation CH 3 H H CH 3 CH 3 Hydrolysis, H + H Condensation CH 3 H 3 C H H 3 C CH 3 CH 3 Acidolysis H CH 3
Content The lignin structure in wood chemistry in pulping Technical lignins
Biomass tree showing the main chemical outlets Ref. Rintekno oy, 1984
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
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 for fuel and for chemicals n a longer term, gasification of biomass to syngas (biodiesel) will be developed
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
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-sugarfermentation; lignin as byproduct Thermochemical pathways to biofuels; 1) lignocellulosics pyrolysis-bio oil-biofuels 2) lignocellulosics gasification-methanol/ft-fuels
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,..)
Biomass composition Structure Softwood Hardwood Wheat straw (Picea abies) (Betula verrucosa) Cellulose 42 42 38 Hemicellulose (C6-sugars) 19 4 1 Hemicellulose (C5-sugars) 7 26 24 27 23 24 Extractives 2 3 3 ther components 3 2 10
The ideal separation of biomass
and the reality Kraft and soda pulping Sulfite pulping Acid hydrolysis Steam explosion rganosolv pulping At present, none of these processes results in an efficient and cheap separation
Elemental analysis Sample carbon hydrogen oxygen sulfur Kraft lignin, pine 64.3 6.0 27.9 1.8 Kraft lignin, birch 63.5 6.1 28.0 2.4 Kraft lignin, E. globulus 56.1 5.7 35.4 2.8 Soda lignin, bagasse 61.8 6.0 32.2 0 Steam explosion, beech 57.6 6.0 36.4 0
Substance Groups in Kraft Black Liquors (kg/ton of pulp) Fraction Pine Birch Hydroxycarboxylic acids Acetic acid Misc. products 490 320 50 200 330 230 120 170 Ref: Sjöström 1993
Principle for manufacturing of lignin from kraft black liquor Black liquor Acid: C 2 or H 2 S 4 Evaporation Precipitation ph = 9 Filtration, Washing Filtrate, wash water Flash drying
Solvent fractionation of softwood kraft lignin Fraction Yield M n M w M w /M n CH 2 Cl 2 9 4.5 x 10 2 6.2 x 10 2 1.4 n-propanol 22 9.0 x 10 2 1.3 x 10 3 1.4 Methanol 26 1.7 x 10 3 2.9 x 10 3 1.7 CH 3 H/CH 2 Cl 2 28 3.8 x 10 3 8.2 x 10 4 22 Undissolved 14 5.8 x 10 3 1.8 x 10 5 31 Unfractionated 100 1.4 x 10 3 3.9 x 10 4 28 Ref: Kringstad et al
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 Permeate Retentate isolation: Precipitation with C 2 (ph 9), Acid washing with H 2 S 4 (ph 2.3), Drying Purification: Cation-exchange to remove traces of Me +
SEC of kraft lignins before/after fractionation softwood eucalypt SWL EL SP5 EP5 dw/d log M SR5 dw/d log M ER5 0 1 2 3 4 5 6 log M (relative polystyrene) 0 1 2 3 4 5 6 log M (relative polystyrene)
SEC-data from fractionated (5 kda) kraft lignins Sample/ SW SW SW Euc. Euc. Euc. polymer data lignin permeate retentate lignin permeate retentate M w 5600 1800 6100 2300 1300 3400 M n 900 450 900 530 440 660 Polydispersity 6.2 3.9 6.8 4.4 3.0 5.1
Thermal analysis of purified kraft lignins sample/ SW SW SW Euc. Euc. Euc. thermal data lignin permeate retentate lignin permeate retentate T g, o C 148 130 157 133 119 142 T s, o C - 181 - - 182 - T d, o C 267 260 261 264 260 248
Even a small lignin withdrawal can be interesting 650,000 tonnes of pulp withdrawal of 10% yields 33,000 tonnes converted to 16,000 tonnes of CF to support 160,000 cars with CF-composite (~40% replacement)
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