Aqueous fractionation of biomass based on novel carbohydrate hydrolysis kinetics

• US 6,228,177 B1
• Filed: 04/14/1999
• Issued: 05/08/2001
• Est. Priority Date: 09/30/1996
• Status: Expired due to Term

• Current Assignee: Alliance For Sustainable Energy LLC
• Original Assignee: Midwest Research Institute
• Inventors: Torget, Robert W.
• Primary Examiner(s): Bell, Mark L.
• Assistant Examiner(s): Hailey, Patricia L.
• Application Number:
  US09/292,770
• Time in Patent Office: 755 Days
• Field of Search: 127/1, 127/37, 435/105, 536/56, 536/124, 536/127
• US Class Current: 127/37
• CPC Class Codes: C07G 99/00 Subject matter not provided for in other groups of this subclass
• CPC Class Codes: C08H 8/00 Macromolecular compounds derived from lignocellulosic materials pretreatment thereof B27N
• CPC Class Codes: C13K 1/02 obtained by saccharification of cellulosic materials manufacture of fodder A23K10/32
• CPC Class Codes: D21C 3/04 with acids, acid salts or acid anhydrides D21C3/003 and D21C3/222 take precedence

Abstract

A multi-function process for hydrolysis and fractionation of lignocellulosic biomass to separate hemicellulosic sugars from other biomass components comprising extractives and proteins; a portion of a solubilized lignin; cellulose; glucose derived from cellulose; and insoluble lignin from said biomass comprising:

a) introducing either solid fresh biomass or partially fractioned lignocellulosic biomass material with entrained acid or water into a reactor and heating to a temperature of up to about 185° C.-205° C.

b) allowing the reaction to proceed to a point where about 60% of the hemicellulose has been hydrolyzed in the case of water or complete dissolution in case of acid;

c) adding a dilute acid liquid at a pH below about 5 at a temperature of up to about 205° C. for a period ranging from about 5 to about 10 minutes; to hydrolyze the remaining 40% of hemicellulose if water is used.

d) quenching the reaction at a temperature of up to about 140° C. to quench all degradation and hydrolysis reactions; and

e) introducing into said reaction chamber and simultaneously removing from said reaction chamber, a volumetric flow rate of dilute acid at a temperature of up to about 140° C. to wash out the majority of the solubilized biomass components, to obtain improved hemicellosic sugar yields.

Claims

1. In a multi-function process for hydrolysis and fractionation of lignocellulosic biomass to separate hemicellulosic sugars from other biomass components comprising extractives and proteins;

a portion of a solubilized lignin;

cellulose;

glucose derived from cellulose; and

insoluble lignin from said biomass, the improvement comprising;

a) introducing either solid fresh biomass or partially fractioned lignocellulosic biomass material containing entrained water or acid at pH<

5.0 into a reactor and heating to a temperature from about 185°

C. to about 205°

C.;

b) allowing the reaction to proceed to a point where about 60% by weight of the hemicellulose has been hydrolyzed, in the case of water only for about 6-10 minutes, or in the case when acid is present for about 5-10 minutes for complete dissolution;

c) adding a dilute acid liquid at a pH below about 5.0 at a temperature of up to about 205°

C. for a period ranging from about 5 to about 10 minutes when water is used in step b);

d) quenching the reaction at an average temperature of up to about 140°

C. to quench all degradation and hydrolysis reactions; and

e) introducing into said reaction chamber and simultaneously removing from said reaction chamber, a volumetric flow rate of dilute acid at an average temperature of up to about 140°

C. to wash out the majority of the solubilized biomass components, to obtain improved hemicellulosic sugar yields and prevent recondensation reactions from occuring.

2. The process of claim 1, wherein, in step (e) said dilute acid is introduced in an amount about 2 times the volume of the reaction chamber.

3. The process of claim 1 wherein said dilute acid is a mineral acid or carbonic acid.

4. The process of claim 3, wherein said mineral acid is selected from the group consisting of sulfuric acid, phosphoric acid, and nitric acid.

5. The process of claim 4, wherein said dilute acid is sulfuric acid.

6. The process of claim 5, wherein in step (c), 0.15 weight percent of sulfuric acid is used, and in step e, 0.07 weight percent of sulfuric acid is used.

7. The process of claim 6 in which the reactor is a plug flow reactor.

8. The process of claim 7 in which the reactor is a continual shrinking bed reactor.

9. The process of claim 8, in which said continual shrinking bed reactor comprises means to allow the biomass to fall back to maintain a constant solid to liquid ratio.

10. The process of claim 9 wherein the volumetric flow rate is sufficient to keep the solid and liquid at a constant ratio throughout said process so as to increase the linear velocity.

11. The process of claim 6 wherein, in step (e), said majority of the solubilized biomass components is 80 to 100 weight percent.

12. The process of claim 11, wherein said biomass is yellow poplar.

13. The process of claim 12, wherein said biomass is corn stover, rice-straw, a soft wood mix, bagasse, or clarified municipal solid waste.