Concentrated sulfuric acid process for converting lignocellulosic materials to sugars

• US 5,188,673 A
• Filed: 10/12/1988
• Issued: 02/23/1993
• Est. Priority Date: 05/15/1987
• Status: Expired due to Term

• Current Assignee: Edgar C. Clausen, James L. Gaddy
• Original Assignee: Edgar C. Clausen, James L. Gaddy
• Inventors: Gaddy, James L., Clausen, Edgar C.
• Primary Examiner(s): MYERS, HELANE ELEANORA
• Application Number:
  US07/256,716
• Time in Patent Office: 1,595 Days
• Field of Search: 127/37, 127/1, 530/500
• US Class Current: 127/37
• CPC Class Codes: C13K 1/02 obtained by saccharification of cellulosic materials manufacture of fodder A23K10/32
• CPC Class Codes: C13K 13/002 Xylose

Abstract

A single step method of converting lignocellulosic materials to sugars including combining and mixing a low solids content lignocellulosic material with concentrated sulfuric acid, allowing the reaction to proceed and then separating the sulfuric acid and sugar solution from the reaction product. A modified single step method includes dilution of the reaction product with water, followed by continued reaction and subsequent separation of the sulfuric acid and sugar solution.

Claims

1. A method of converting lignocellulosic materials to sugars comprising the steps of:

combining a lignocellulosic material with sulfuric acid in a reaction vessel such that the resulting combination of lignocellulosic material and sulfuric acid has a lingnocellulosic material solids content of 2% to about 10% by weight and the sulfuric acid has a concentration of at least 30% by weight;

mixing said lignocellulosic material and sulfuric acid combination at a temperature of less than 100°

C. to cause an hydrolysis reaction to convert said lignocellulosic material to sugars and allowing such hydrolysis reaction to continue until such conversion of lignocellulosic material to sugars is substantially complete; and

separating the sulfuric acid and sugars from the product of such reaction.

2. The method of claim 1 wherein the combination of said lignocellulosic material and sulfuric acid has a lignocellulosic material solids content of less than about 5% by weight.

3. The method of claim 1 wherein said sulfuric acid in said combination of lignocellulosic material and sulfuric acid has a concentration of at least 50% by weight.

4. The method of claim 1 wherein said sulfuric acid in said combination of lignocellulosic material and sulfuric acid has a concentration of at least 70% by weight.

5. The method of claim 1 including preparing said lignocellulosic material by reducing it to a mesh size of less than about 30.

6. The method of claim 1 wherein the separation of sulfuric acid and sugars includes filtering the sulfuric acid and sugars from the product of such reaction.

7. The method of claim 1 wherein said lignocellulosic material is unhydrolyzed.

11. The method of claim 7 including preparing said lignocellulosic material by reducing it to a mesh size of less than about 30.

8. A method of converting lignocellulosic materials to sugars comprising the steps of:

combining a lignocellulosic material with sulfuric acid in a reaction vessel such that the resulting combination of lignocellulosic material and sulfuric acid has a lignocellulosic material solids content of less than about 30% by weight and the sulfuric acid has a concentration of at least 30% by weight;

mixing said lignocellulosic material and sulfuric acid combination at a temperature of less than 100°

C. to cause an hydrolysis reaction to convert said lignocellulosic material to a mixture of polymeric and monomeric sugars and allowing such hydrolysis reaction to continue until such conversion of lignocellulosic material to polymeric and monomeric sugars is substantially complete;

diluting said mixture by adding water until the sulfuric acid concentration therein is less than about 50% by weight;

mixing the resulting diluted mixture at a temperature of less than 100°

C. to cause a reaction to convert polymeric sugars to monomeric sugars and allowing said converting reaction to continue until the conversion of polymeric sugars to monomeric sugars is substantially complete; and

separating the sulfuric acid and sugars from the resulting product.

9. The method of claim 8 wherein said dilution step includes diluting the sulfuric acid to a concentration of less than about 40% by weight.

10. The method of claim 8 wherein said sulfuric acid in the combination of lignocellulosic material and sulfuric acid has a concentration of at least 70% by weight.

12. The method of claim 8 wherein the separtion of sulfuric acid and sugars from the diluted product reaction includes filtering.

13. A method of converting lignocellulosic materials to sugars consisting essentially of the steps of:

combining a lignocellulosic material with sulfuric acid in a reaction vessel such that the resulting combination of lignocellulosic material and sulfuric acid has a lignocellulosic material solids content of 2% to about 10% by weight and the sulfuric acid has a concentration of at least 30% by weight;

mixing said lignocelulosic material and sulfuric acid combination at a temperature of less than 100°

C. to cause an hydrolysis reaction to convert said lignocellulosic material to sugars and allowing such hydrolysis reaction to continue until such conversion of lignocellulosic material to sugars is substantially complete; and

separating the sulfuric acid and sugars from the product of such reaction.