Methods of making specialized lignin and lignin products from biomass
Provided are cost-effective methods and systems for producing a low molecular weight reactive lignin from a lignocellulosic biomass. The process is rapid and the reactive lignin is easily separated from carbohydrates and other components of the biomass at low cost. This clean lignin product has a very low molecular weight, good hydroxyl content, and low ash and sulfur, making it valuable to many applications.
1. A method for producing a reactive lignin from a biomass, the method comprising:
(a) pretreating the biomass with acid and steam explosion to produce: (1) a liquid component comprising a solubilized first carbohydrate fraction, and (2) a solid component comprising a second carbohydrate fraction and a first lignin fraction;
(b) separating the liquid component from the solid component;
(c) treating the solid component with a pH of at least 8 to solubilize the first lignin fraction and precipitate the second carbohydrate fraction;
(d) separating the solubilized first lignin fraction from the precipitated second carbohydrate fraction;
(e) treating the solubilized first lignin fraction with a pH of at least 7 to produce a second lignin fraction that is precipitated and a third lignin fraction that is solubilized;
(f) separating the second lignin fraction from the third lignin fraction; and
(g) treating the third lignin fraction with a pH of 5 or lower to precipitate the reactive lignin,
wherein the reactive lignin has a molecular weight (M w ) under 3000 Da, a molar mass (M n ) under 1700 Da, and a sulfur content under 2.5 wt. %.
2. The method of claim 1 , wherein the duration of the pretreating step is less than 30 seconds.
3. The method of claim 1 , wherein the first lignin fraction is solubilized by an alkali.
4. The method of claim 1 , wherein the first lignin fraction is solubilized by raising the pH of the solid component.
5. The method of claim 4 , wherein the pH is raised to about 8.5, about 9.0, about 9.5, about 10.0, about 10.5, or about 11.
6. The method of claim 4 , wherein the pH is raised by a chemical agent selected from the group consisting of: sodium hydroxide, calcium hydroxide, potassium hydroxide, ammonia, ammonia hydroxide, hydrogen peroxide, and a combination thereof.
7. The method of claim 1 , wherein the first lignin fraction is solubilized by a solvent.
8. The method of claim 7 , wherein the solvent is selected from the group consisting of: an organosolv, an ionic liquid, and a combination thereof.
9. The method of claim 1 , wherein the first lignin fraction is separated from the second carbohydrate fraction by centrifugation, filtration, membrane filtration, diafiltration, or flocculation.
10. The method of claim 1 , further comprising separating the reactive lignin by centrifugation, filtration, membrane filtration, diafiltration, or flocculation.
11. The method of claim 1 , wherein the second lignin fraction is separated from the third lignin fraction by centrifugation, filtration, membrane filtration, diafiltration, or flocculation.
12. The method of claim 1 , wherein the reactive lignin is precipitated with an acid.
13. The method of claim 12 , wherein the acid is selected from the group consisting of: sulfuric acid, peroxyacetic acid, hydrochloric acid, phosphoric acid, oxalic acid, lactic acid, formic acid, acetic acid, citric acid, benzoic acid, sulfurous acid, chloroacetic acid, dichloroacetic acid, trichloroacetic acid, and a combination thereof.
14. The method of claim 1 , further comprising decolorizing the reactive lignin with a decolorizing agent.
15. The method of claim 14 , wherein the decolorizing agent is H 2 O 2 .
16. The method of claim 1 , wherein the biomass is selected from the group consisting of:
silage, agricultural residues, corn stover, bagasse, sorghum, nuts, nut shells, coconut shells, Distillers Dried Solubles, Distillers Dried Grains, Condensed Distillers Solubles Distillers Wet Grains, Distillers Dried Grains with Solubles, woody materials, sawdust, wood chips, timber slash, mill scrap, municipal waste, waste paper, recycled toilet papers, yard clippings, poplars, willows, switchgrass, alfalfa, and prairie bluestem, non-woody plant matter, cellulosic material, lignocellulosic material, hemicellulosic material, carbohydrates, corn, sugar cane, grasses, switchgrass, high biomass sorghum, bamboo, corncobs, and peels and pits.
17. The method of claim 1 , wherein a total hydroxyl content of the reactive lignin is higher than 5.00 mmol/g.
18. The method of claim 1 , wherein the molecular weight of the reactive lignin is under 2500 Da.
19. The method of claim 1 , wherein the sulfur content of the reactive lignin is under 0.50 wt. %.
20. The method of claim 1 , comprising treating the solubilizedfirst lignin fraction with a pH of about 9.