Method of removing silica or silicates from solids resulting from the strong acid hydrolysis of cellulosic and hemicellulosic materials

• US 5,782,982 A
• Filed: 06/07/1995
• Issued: 07/21/1998
• Est. Priority Date: 03/26/1993
• Status: Expired due to Term

• Current Assignee: Arkenol, Inc.
• Original Assignee: Arkenol, Inc.
• Inventors: Farone, William A., Cuzens, John E.
• Primary Examiner(s): Caldarola, Glenn
• Assistant Examiner(s): Hailey, Patricia L.
• Application Number:
  US08/483,454
• Time in Patent Office: 1,140 Days
• Field of Search: 423/333, 423/338, 127/1, 127/36, 127/37, 536/124, 536/127, 536/1.11
• US Class Current: 127/37
• CPC Class Codes: C08B 15/02 Oxycellulose; Hydrocellulose; Cellulosehydrate, e.g. microcrystalline cellulose
• 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 7/10 substrate containing cellulosic material
• CPC Class Codes: C13B 20/144 using only cationic ion-exchange material C13B20/148 takes precedence
• CPC Class Codes: C13K 1/02 obtained by saccharification of cellulosic materials manufacture of fodder A23K10/32
• CPC Class Codes: C13K 1/04 Purifying
• CPC Class Codes: Y02E 50/10 Biofuels, e.g. bio-diesel

Abstract

A method of removing silica or silicates from solids results from the acid hydrolysis of materials containing cellulose and hemicellulose is disclosed. The method includes the steps of treating the solids with a metal hydroxide solution to produce an extract, reducing the pH of the extract to produce silicic acid, and removing the silicic acid from the extract.

Claims

1. A method of removing silica or silicates from materials containing cellulose and hemicellulose, comprising:

mixing the materials with a solution of about 25-90% acid by weight, thereby at least partially decrystalizing the materials and forming a gel that includes a solid and a liquid portion;

diluting said gel to an acid concentration of from about 20% to about 30% by weight and heating said gel, thereby at least partially hydrolyzing the cellulose and hemicellulose contained in said materials;

separating said liquid portion from said solid material;

treating the solid material with a metal hydroxide solution to produce an extract;

reducing the pH of the extract to produce silicic acid; and

removing said silicic acid from said extract.

2. The method of claim 1, wherein the treating step comprises treating with a solution of sodium hydroxide.

3. The method of claim 2, wherein said sodium hydroxide is at a concentration of from about 5% to about 10%.

4. The method of claim 1, wherein said treating step is performed at a temperature of between about 60°

-80°

C.

5. The method of claim 1, wherein said treating step is performed for about 60-90 minutes.

6. The method of claim 1, wherein the removal of said silicic acid is done by filtering said extract.

7. The method of claim 6, further comprising neutralizing the extract remaining after filtering.

8. The method of claim 1, wherein the reducing is done with an acid selected from the group consisting of sulfuric, hydrochloric, hydrofluoric, and phosphoric.

9. The method of claim 1, further comprising producing silica gel, silicic acid and sodium silicate from the silicic acid.

10. The method of claim 1, further comprising mixing the silicic acid with aluminum salts and drying the mixture to produce zeolites.

11. The method of claim 10, wherein the Brunauer-Emmet-Teller (BET) surface area to nitrogen absorption of the zeolites produced is at least 300 m² /g.

12. A method of removing silica or silicates from solids resulting from the acid hydrolysis of materials containing cellulose and hemicellulose, comprising:

treating the solids with a metal hydroxide solution to produce an extract;

reducing the pH of the extract to produce silicic acid;

removing the silicic acid from said extract; and

treating the silicic acid with an oxidizing agent to reduce the color of the silicic acid.

13. The method of claim 12, wherein the oxidizing agent is selected from the group consisting of sodium hypochlorite, hydrogen peroxide, ozone, chlorine, and chlorine dioxide.

14. A method of removing silica or silicates from solids resulting from the acid hydrolysis of materials containing cellulose and hemicellulose, comprising:

treating the solids with a metal hydroxide solution to produce an extract;

reducing the pH of the extract to produce silicic acid; and

removing said silicic acid from said extract by filtering the extract;

wherein the metal hydroxide solution is a solution of sodium hydroxide, wherein said reducing is done with sulfuric acid, and further comprising adding lime to the extract remaining after filtering to remove silicic acid to produce calcium sulfate and sodium hydroxide.