Methods for removing hemicellulose

• US 8,980,050 B2
• Filed: 03/14/2013
• Issued: 03/17/2015
• Est. Priority Date: 08/20/2012
• Status: Active Grant

• Current Assignee: Celanese International Corporation (Celanese Corporation)
• Original Assignee: Celanese International Corporation (Celanese Corporation)
• Inventors: Li, Rongfu, Mehta, Jay, Tu, Xiaoyan, Bansal, Prabuddha, Combs, Michael, Fallon, Denis, Kizer, Lawton E
• Primary Examiner(s): Halpern, Mark
• Application Number:
  US13/827,837
• Publication Number:
  US 20140048222A1
• Time in Patent Office: 733 Days
• Field of Search: 162/14, 162/17, 162/19, 162/37, 162 72- 76, 162/141, 162/234, 530/500, 536/123.1, 536/56
• US Class Current: 162/14
• CPC Class Codes: C08B 37/0057 beta-D-Xylans, i.e. xylosaccharide, e.g. arabinoxylan, arabinofuronan, pentosans; (beta-1,3)(beta-1,4)-D-Xylans, e.g. rhodymenans; Hemicellulose; Derivatives thereof
• CPC Class Codes: C08H 8/00 Macromolecular compounds derived from lignocellulosic materials pretreatment thereof B27N
• CPC Class Codes: C12P 19/04 Polysaccharides, i.e. compounds containing more than five saccharide radicals attached to each other by glycosidic bonds
• CPC Class Codes: C12P 19/14 produced by the action of a carbohydrase (EC 3.2.x), e.g. by alpha-amylase , e.g. by cellulase, hemicellulase
• CPC Class Codes: D21C 3/20 with organic solvents or in solvent environment
• CPC Class Codes: D21C 9/005 organic compounds
• CPC Class Codes: D21C 9/007 by mechanical or physical means

Abstract

A method for treating a cellulosic material comprising extracting the cellulosic material with an extractant to selectively extract hemicellulose therein and separating the extracted hemicellulose to form a cellulosic product comprising less hemicellulose than the cellulosic material. The extractant comprises an amine oxide and a non-solvent. The cellulosic product retains the cellulosic fiber morphology.

Claims

1. A method for treating a cellulosic material, comprising:

extracting the cellulosic material with an extractant to selectively extract hemicellulose, wherein the extractant comprises an amine oxide and a non-solvent; and

separating the extracted hemicellulose from the cellulosic material to form a cellulosic product comprising less hemicellulose than the cellulosic material.

2. The method of claim 1, wherein the extractant selectively extracts at least 20% of hemicellulose in the cellulosic material.

3. The method of claim 1, wherein less than 15% of the cellulose in the cellulosic material is extracted.

4. The method of claim 1, wherein the cellulosic product retains a cellulosic fiber morphology.

5. The method of claim 1, wherein the amine oxide is selected from the group consisting of n-methylmorpholine n-oxide, pyridine N-oxide, R₁R₂R₃N—

O, wherein R₁, R₂ and R₃ are alkyls with chain length from 1 to 12.

6. The method of claim 1, wherein the non-solvent is selected from the group consisting of water, dimethyl sulfoxide, dimethylformamide, alcohol, N-methylpyrrolidone, and mixtures thereof.

7. The method of claim 1, wherein the extractant comprises at least 50 wt. % amine oxide and at least 20 wt. % non-solvent.

8. The method of claim 1, wherein the extractant comprises at least 50 wt. % n-methylmorpholine n-oxide and at least 20 wt. % water.

9. The method of claim 1, wherein the extractant comprises at least 0.8 wt. % n-methylmorpholine n-oxide, at least 0.01 wt. % water, and at least 50 wt. % dimethyl sulfoxide.

10. The method of claim 1, further comprising treating the cellulosic product with an enzyme.

11. The method of claim 10, wherein the enzyme is a hemicellulase.

12. The method of claim 1, wherein the extracting step is conducted at a temperature from 30°

C. to 150°

C.

13. The method of claim 1, wherein the extracting step is between 5 minutes to 180 minutes.

14. The method of claim 1, further comprising washing the cellulosic product with at least one of dimethyl sulfoxide, dimethylformamide, N-methylpyrrolidone, methanol, ethanol, isopropanol, dimethyl carbonate, acetone and/or water.

15. The method of claim 1, wherein the cellulosic product has an absorbance of less than 2.0 at 277 nm.

16. The method of claim 1, wherein the cellulosic material comprises wood pulp.

17. The method of claim 16, wherein the cellulosic material comprises paper grade wood pulp.

18. The method of claim 16, wherein the cellulosic material comprises less than 90% α

-cellulose.

19. The method of claim 1, wherein the extracting comprises batch, co-current, or counter-current extraction.

20. The method of claim 1, wherein the extracting comprises use of an agitated tank, hydrapulper, screw conveyor or screw extractor.

21. The method of claim 1, wherein solid and liquid phases are separated by a filter or centrifuge.

22. A method for producing high purity α

-cellulose grade pulp, comprising;

extracting hemicellulose from a wood pulp by treating the wood pulp with an extractant comprising an amine oxide and a non-solvent to form an intermediate wood pulp that retains a cellulosic fiber morphology;

treating the intermediate wood pulp with an enzyme to hydrolyze the hemicellulose contained therein to form a reduced hemicellulose wood pulp; and

washing the reduced hemicellulose wood pulp with a wash solution to form the high purity α

-cellulose grade pulp.

23. The method of claim 22, wherein the high purity α

-cellulose grade pulp has an absorbance of less than 1.5 at 277 nm.

24. The method of claim 22, wherein at least 50% of the hemicellulose is removed from the wood pulp.

25. The method of claim 22, further comprising repeating the extraction step to remove additional hemicellulose.

26. The method of claim 22, wherein the extracting comprises batch, co-current, or counter-current extraction.

27. The method of claim 22, wherein the extracting comprises use of an agitated tank, hydrapulper, screw conveyor or screw extractor.

28. The method of claim 22, wherein solid and liquid phases are separated by a filter or centrifuge.