Process for the Treatment of Lignocellulosic Biomass

• US 20090221042A1
• Filed: 04/30/2007
• Published: 09/03/2009
• Est. Priority Date: 05/01/2006
• Status: Active Grant

• Current Assignee: The Trustees of Dartmounth College (Dartmouth College), The Board of Trustees of Michigan State University (Michigan State University)
• Original Assignee: The Trustees of Dartmounth College (Dartmouth College)
• Inventors: Laser, Mark, Dale, Bruce E., Lynd, Lee R.
• Granted Patent: US 8,394,611 B2
• Time in Patent Office: Days
• US Class Current: 435/105
• CPC Class Codes: C12P 19/02 Monosaccharides 2-ketogulonic acid C12P7/60
• CPC Class Codes: C12P 2201/00 Pretreatment of cellulosic or lignocellulosic material for subsequent enzymatic treatment or hydrolysis
• CPC Class Codes: C12P 7/10 substrate containing cellulosic material
• CPC Class Codes: C13K 1/02 obtained by saccharification of cellulosic materials manufacture of fodder A23K10/32
• CPC Class Codes: C13K 13/002 Xylose
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel

Abstract

A process for the treatment of biomass to render structural carbohydrates more accessible and/or digestible using concentrated ammonium hydroxide with or without anhydrous ammonia addition, is described. The process preferably uses steam to strip ammonia from the biomass for recycling. The process yields of monosaccharides from the structural carbohydrates are good, particularly as measured by the enzymatic hydrolysis of the structural carbohydrates. The monosaccharides are used as animal feeds and energy sources for ethanol production.

Claims

1. A process for the treatment of structural carbohydrates in lignocellulosic biomass which comprises:

(a) reacting the biomass with a heated aqueous ammonium hydroxide solution having a concentration greater than about 30% by weight ammonia in a closed vessel at 50°

C. or above at an elevated pressure from atmospheric pressure while simultaneously manipulating the temperature, a mass ratio of ammonia to a dry biomass and a mass ratio of water to the dry biomass to increase the digestibility and/or accessibility of the structural carbohydrates;

(b) rapidly releasing the pressure in the vessel;

(c) recovering at least some of the ammonia and ammonium hydroxide from the biomass and the solution; and

(d) optionally further processing the treated biomass via enzymes, microbial conversion or animal digestive processes.

2. The process of claim 1 wherein the structural carbohydrates are recovered as a mixture of glucose, xylose, arabinose and other sugars in step (d).

3. The process of claim 1 wherein the structural carbohydrates made available by the further treatment which is the microbial conversion which produces organic acids, alcohols, and other byproducts.

4. The process of claim 1 wherein the carbohydrates made available by the process are utilized by the animal digestive processes in either ruminant or non-ruminant animal diets.

5. The process of claim 1 wherein the temperature of the mixture of ammonia, biomass and water in the closed vessel is at a temperature between about 50°

C. and 120°

C.

6. The process of claim 1 wherein the pressure in the closed vessel is between about 4 and 50 atm.

7. The process of claim 1 wherein ammonia gas is added to the vessel to fill any void space in the vessel.

12. The process of claim 1 wherein the pressure is released rapidly.

8. A process for the treatment of a lignocellulosic containing plant biomass comprising structural carbohydrates with water naturally present in the biomass to produce more digestible or accessible structural carbohydrates which comprises:

(a) reacting the biomass with a heated aqueous ammonium hydroxide solution in an amount greater than about 30% by weight ammonia in the aqueous ammonium hydroxide solution in a closed vessel at an elevated pressure and at an elevated temperature without degrading the lignocellulose to remove the structural carbohydrates from the biomass into the solution, wherein an amount of water provided with the biomass is greater than 1% by weight and less than 50% by weight of the biomass;

(b) releasing the pressure in the biomass in the vessel;

(c) removing a slurry of the biomass with the structural carbohydrates from the vessel; and

(d) stripping the ammonium hydroxide solution and ammonia from the slurry to provide the structural carbohydrates in the slurry, wherein greater than 85% of the available glucose in the structural carbohydrates can be recovered as a result of enzymatic hydrolysis of the structural carbohydrates.

9. The process of claim 8 wherein the sugars comprise a mixture of xylose and glucose.

10. The process of claim 8 wherein a temperature of the mixture of ammonia, biomass and water in the closed vessel is between about 50 and 120°

C.

11. The process of claim 8 wherein ammonia gas is added to fill any void space in the vessel.

13. The process of claim 8 wherein the pressure is released rapidly.

14. The process of claim 8 wherein the pressure is between about 6.9 and 20.7 atm.

15. A process for recovery of ammonia from an ammonia fiber explosion (AFEX) treatment of a lignocellulosic biomass which comprises:

(a) treating the biomass with an aqueous solution of ammonium hydroxide in a closed reaction vessel under pressure to form a slurry;

(b) releasing the pressure in the vessel of the reaction vessel and pumping the slurry to a stripping column;

(c) stripping ammonia from an upper portion of the stripping column, using steam under pressure with removal of a stripped slurry from a bottom portion of the column;

(d) introducing the stripped ammonia from the upper portion of the column into a mixer and adding water under pressure to the mixer to form a diluted aqueous ammonia solution;

(e) cooling the diluted aqueous ammonia solution from the mixer; and

(f) introducing the cooled aqueous ammonia solution into the reaction vessel along with the additional biomass under pressure.

16. The process of claim 15 wherein the reaction is continuous.

17. A system for performing the process of claims 15 or 16.