Solvent and recovery process for lignin

Patent metadata

Field	Value
Publication number	US-2016137680-A1
Application number	US-201514945846-A
Country	US
Kind code	A1
Filing date	Nov 19, 2015
Priority date	Nov 19, 2014
Publication date	May 19, 2016
Grant date	—

Abstract

Methods for obtaining purified lignin and the lignin that can be obtained by the methods are described. Methods include processing pretreated lignocellulosic biomass feedstock to recover the lignin and provide a lignin composition with a very low level of impurities such as metals and ash. In addition, the lignin recovered from the process can have a narrow molecular weight distribution and, depending upon the specific stages utilized in the process, can have a predetermined molecular weight. The process includes one or more separation stages in which a lignin-containing feedstock is mixed with a solvent solution. The mixture fractionates to form a solvent-rich liquid phase and a lignin-rich liquid phase, the lignin being partitioned across the phases according to the molecular weight of the lignin. Furthermore, the metal salts of the pretreated lignocellulosic biomass feedstock also partition across the phases.

First claim

What is claimed is:

1 . A method for recovering lignin comprising:
combining a pretreated lignocellulosic biomass feedstock containing lignin with a solvent solution to form a mixture; following the combination, the lignin solvating into the solvent solution and the mixture separating into a first fraction and a second fraction, the first fraction comprising a solvent-rich liquid phase and the second fraction comprising a lignin-rich liquid phase, wherein the first fraction comprises a first portion of the lignin of the feedstock and the second fraction comprises a second portion of the lignin of the feedstock, the lignin of the first fraction differing from the lignin of the second fraction; and recovering the lignin of the first fraction and/or the lignin of the second fraction.

2 . The method of claim 1 , wherein the average number average molecular weight of the first portion of the lignin differs from the average number average molecular weight of the second portion of the lignin.

3 . The method of claim 2 , wherein the first portion of the lignin has a lower average number average molecular weight as compared to the average number average molecular weight of the lignin of the pretreated lignocellulosic biomass feedstock.

4 . The method of claim 2 , wherein the second portion of the lignin has a higher average number average molecular weight as compared to the average number average molecular weight of the lignin of the pretreated lignocellulosic biomass feedstock.

5 . The method of claim 1 , the pretreated lignocellulosic biomass feedstock comprising metal, the metals content of the first fraction differing from the metals content of the second fraction.

6 . The method of claim 5 , the second fraction comprising 50% or less by weight of the metal of the pretreated lignocellulosic biomass feedstock.

7 . The method of claim 1 , the pretreated lignocellulosic biomass feedstock comprising ash, the ash content of the first fraction differing from the ash content of the second fraction.

8 . The method of claim 1 , the solvent solution comprising water, an organic solvent, an inorganic acid, or mixtures thereof.

9 . The method of claim 8 , the organic solvent comprising a C 1 to C 8 organic solvent that has at least one functional group in common with the lignin of the pretreated lignocellulosic biomass feedstock.

10 . The method of claim 9 , wherein the organic solvent comprises an organic acid, an aliphatic alcohol, an ether, a ketone, or a mixture thereof.

11 . The method of claim 10 , wherein the organic acid comprises formic acid, acetic acid, propanoic acid, butanoic acid, oxalic acid, or mixtures thereof.

12 . The method of claim 1 , further comprising heating the mixture, the lignin solvating into the solvent solution upon the heating of the mixture.

13 . The method of claim 1 , wherein the first portion of the lignin and/or the second portion of the lignin have a narrower molecular weight distribution as compared to the molecular weight distribution of the lignin of the pretreated lignocellulosic biomass feedstock.

14 . The method of claim 1 , further comprising combining the second fraction with a second solvent solution to form a second mixture, wherein following this combination optionally with heating, the second mixture separates into a third fraction and a fourth fraction, the third fraction being a solvent-rich liquid phase and the fourth fraction being a lignin-rich liquid phase.

15 . The method of claim 1 , further comprising combining the first fraction with a third solvent solution to form a third mixture, wherein following this combination optionally with heating the third mixture separates into a fifth fraction and a sixth fraction, the fifth fraction being a solvent-rich liquid phase and the sixth fraction being a lignin-rich liquid phase.

16 . The method of claim 1 , further comprising two or more separation stages during which a lignin-containing feed from a previous stage is combined with a solvent solution to form a mixture and wherein upon this combination optionally with heating the mixture separates to form two fractions, one of which is a solvent-rich phase and the other of which is a lignin-rich phase.

17 . The method of claim 1 , further comprising precipitating the lignin of the first fraction and/or the second fraction.

18 . The method of claim 1 , wherein the method is carried out at a temperature and a pressure such that both the lignin-rich phase and the solvent-rich phase remain below vaporization conditions.

19 . The method of claim 1 , further comprising solution spinning or melt spinning at least a portion of the recovered lignin to form a polymeric fiber.

20 . A purified lignin composition comprising lignin having a number average molecular weight and a molecular weight distribution in which about 40 wt. % or more of the lignin is within about 50% or less of the number average molecular weight as determined by gel permeation chromatography.

21 . The purified lignin composition of claim 20 , wherein the composition has a metals content of about 250 ppm or less.

22 . The purified lignin composition of claim 20 , wherein the composition has a combined sodium and potassium content of about 100 ppm or less.

23 . The purified lignin composition of claim 20 , wherein the composition has a sodium content of about 50 ppm or less.

24 . The purified lignin composition of claim 20 , wherein the composition has an ash content of about 0.30 wt. % or less.

25 . The purified lignin composition of claim 20 , wherein the composition has an ash content of about 0.10 wt. % or less.

26 . A purified lignin having a polydispersity index of about 2.0 or less as determined by gel permeation chromatography.

27 . The purified lignin of claim 26 , wherein the lignin is a component of a composition having a metals content of about 250 ppm or less.

28 . The purified lignin of claim 26 , wherein the lignin is a component of a composition having a combined sodium and potassium content of about 100 ppm or less.

29 . The purified lignin of claim 26 , wherein the lignin is a component of a composition having a sodium content of about 50 ppm or less.

30 . The purified lignin composition of claim 26 , wherein the composition has an ash content of about 0.30 wt. % or less.

31 . The purified lignin of claim 26 , wherein the lignin is a component of a composition having an ash content of about 0.1 wt. % or less.

Assignees

• Univ Clemson

Inventors

• Thies Mark C
• Klett Adam S
• Bruce David A

Classifications

• B01D11/00

  Solvent extraction · CPC title

• C07G1/00 Primary

  Low-molecular-weight derivatives of lignin (high-molecular-weight derivatives of lignin {C08H6/00}) · CPC title