PROCESS FOR FRACTIONATING SUGARCANE BAGASSE INTO HIGH A-CELLULOSE PULP, XYLAN AND LIGNIN

• US 20100276093A1
• Filed: 09/05/2008
• Published: 11/04/2010
• Est. Priority Date: 09/07/2007
• Status: Active Grant

• Current Assignee: Council of Scientific & Industrial Research
• Original Assignee: Council of Scientific & Industrial Research
• Inventors: Varma, Anjanikumar Jyotiprasad
• Granted Patent: US 8,529,731 B2
• Time in Patent Office: Days
• US Class Current: 162/55
• CPC Class Codes: C08B 37/0003 General processes for their isolation or fractionation, e.g. purification or extraction from biomass
• 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: D21C 1/02 with water or steam
• CPC Class Codes: D21C 1/08 with oxygen-generating compounds
• CPC Class Codes: D21C 9/14 with ClO2 or chlorites
• CPC Class Codes: D21H 11/12 Pulp from non-woody plants or crops, e.g. cotton, flax, straw, bagasse

Abstract

Sugarcane bagasse consists of mainly three polymeric components, namely cellulose (40-45%), hemicellulose (xylan) (28-30%), and lignin (19-21%). A process is herein disclosed for fractionating sugarcane bagasse into cellulose, hemicellulose and lignin with high purity α-cellulose, which is a useful raw material for preparing cellulose esters like cellulose triacetate and other high value-added cellulose plastics. Co-production and recovery of hemicellulose (xylan) and lignin in high yields and high purities, along with α-cellulose, is another important feature of this process. Sugarcane bagasse consists of a material known as pith which constitutes 30-35% by weight of bagasse. Pith contains cellulose, hemicellulose, and lignin, in addition to various other ingredients and cell mass. The process described herein discloses the use of partially depithed bagasse as a preferred raw material for fractionation. Use of sugarcane bagasse containing pith leads to a product which is lower in yield as well as poorer in color.

Claims

1. A process for the fractionation and isolation of high α

-cellulose pulp, hemicellulose (xylan) and lignin from depithed fibrous organic biomass and the said process comprising the steps of;

a) contacting the biomass with steam, at a temperatures in the range 140°

C.-230°

C., for period of 0.5 minute to 60 minutes, hydrolyzing and solubilizing the hemicellulose component to an extent of 70-90%, followed by evaporation of the condensed water to obtain hemicellulose,

b) separating and washing the undissolved fibrous organic biomass with water and treating it with 10-24% alkali, at a temperatures in the range 80-180°

C. to solubilize the lignin component to an extent of 90-95% as well as solubilizing the residual hemicellulose to obtain a soluble fraction containing lignin, followed by precipitation of lignin out with mineral acid,

c) separating and washing the undissolved fibrous organic biomass and bleaching it with 1-10% by weight of sodium chlorite or chlorine dioxide, at a temperature of 20-90°

C., for a period if 1-18 hrs, at a pH of 3.5-4.0,

d) separating, washing and drying the fibrous organic residue to obtain a pulp containing 90-94% α

-cellulose.

2. A process according to claim 1, wherein the biomass used is selected from the group consisted of grassy material, straw and woody material.

3. A process according to claim 1, wherein the grassy material used is sugarcane bagasse.

4. A process according to claim 1, wherein the extent of pith contained in sugarcane bagasse used is reduced upto about 5% pith content from about 35% pith content naturally available in sugarcane bagasse.

5. A process according to claim 1, wherein the alkali used in step (b) is sodium hydroxide.

6. A process according to claim 1, wherein the mineral acid used for the precipitation of lignin in step (b) is selected from hydrochloric acid, sulfuric acid and nitric acid.

7. A process according to claim 1, wherein the mineral acid used for the precipitation of lignin in step (b) is preferably concentrated hydrochloric acid.

8. A process according to claim 1, wherein the reaction time used for bleaching in step (c) is preferably in the range of 4-6 hours.

9. A process according to claim 1, wherein the yield of 90-94% α

-cellulose content of the pulp is 30-37% by weight of the bagasse raw material used.

10. A process according to claim 1, wherein the yield of isolated hemicellulose is 19-26% by weight of the bagasse raw material used.

11. A process according to claim 1, wherein the yield of isolated lignin is in the range of 15-16% by weight of the bagasse raw material used.