High-density adsorbent and method of producing same

• US 4,999,330 A
• Filed: 02/21/1989
• Issued: 03/12/1991
• Est. Priority Date: 03/22/1988
• Status: Expired due to Term

• Current Assignee: Gaz Metropolitain, Inc. (Énergir, Inc.), Universite Du Quebec A Trois-Rivieres Societe Quebecoise D'Initiatives Petrolieres and Gaz Metropolitain Incorporated
• Original Assignee: Gas Metropolitain & Company Limited, Societe Quebecoise D'Initiatives Petrolieres, Universite Du Quebec A Trois-Rivieres
• Inventors: St-Arnaud, Jean-Marie, Bose, Tapan K., Chahine, Richard
• Primary Examiner(s): KONOPKA, PAUL
• Application Number:
  US07/312,940
• Time in Patent Office: 749 Days
• Field of Search: 502/402, 502/416, 502/417, 502/404, 502/526, 502/159, 206/0.7, 264/29.5, 264/109
• US Class Current: 502/402
• CPC Class Codes: B01J 20/20 comprising free carbon; comprising carbon obtained by carbonising processes
• CPC Class Codes: Y10S 502/526 Sorbent for fluid storage, other than an alloy for hydrogen storage

Abstract

The invention is concerned with a high-density adsorbent comprising a compacted mass of high surface area carbon particles bound together with a binder and defining a network of substantially unobstructed micropores, the mass of carbon particles having been compacted under a pressure sufficient to cause a reduction of about 50 to about 200% in bulk volume of the mass and a corresponding increase of about 50 to about 200% in density, thereby providing a gas storage capacity increase of about 20 to about 100% over that of the high surface area carbon particles in loose or uncompacted form. The high-density adsorbent according to the invention is particularly useful in adsorption storage systems for low-pressure storage of compressed natural gas.

Claims

1. A method of producing a dimensionally stable, high-density adsorbent, comprising the steps of:

a) mixing high surface area carbon particles with a solution of a binder in a solvent to form a slurry and thereby wet each particle of carbon with the solution of binder, said binder being selected from the group consisting of methylcellulose and a polyvinyl alcohol;

b) removing the solvent from the slurry prepared in step (a) to obtain particles of carbon coated with a film of the binder; and

c) compacting the binder-coated particles of carbon under pressure of about 140 to about 600 MPA to provide a compacted mass of high surface area carbon particles bound together and defining a network of substantially to cause a reduction of about 50 to about 200% in bulk volume of the mass and a corresponding increase of about 50 to about 200% in density, thereby obtaining an adsorbent capable of withstanding powdering when subjected to vibration and exhibiting a gas storage capacity increase of about 20 to about 100% over that of the high surface area carbon particles in loose form.

2. A method as claimed in claim 1, wherein prior to mixing said carbon particles with said solution of binder, said carbon particles are dispersed in said solvent to wet same and thereby fill pores in the particles with said solvent.

3. A method as claimed in claim 1, wherein removal of the solvent from the slurry is effected by heating said slurry under agitation to cause evaporation of said solvent.

4. A method as claimed in claim 1, wherein said binder is used in an amount of about 1 to about 10% by weight, based on the total weight of the adsorbent composition.

5. A method as claimed in claim 1, wherein said binder is methylcellulose.

6. A method as claimed in claim 5, wherein said methylcellulose has a viscosity of about 4,000 centipoises, calculated as a 2% solution in water.

7. A method as claimed in claim 1, wherein said binder is a polyvinyl alcohol.

8. A method as claimed in claim 7, wherein in step (c) the compacted particles are heated at a temperature and over a period of time such as to cause uniform melting of said polyvinyl alcohol throughout the compacted mass, while maintaining the compaction pressure.

9. A method as claimed in claim 8, wherein the compacted particles are heated at or slightly above the melting temperature of said polyvinyl alcohol.

10. A method as claimed in claim 8, wherein the compacted particles are heated to said temperature at a heating rate such as to avoid temperature gradients in the compacted mass and thereby prevent surface cracking.

11. A method as claimed in claim 9, wherein said polyvinyl alcohol has a molecular weight of about 125,000 and a melting point of about 200°

C.

12. A method as claimed in claim 11, wherein the polyvinyl alcohol coated carbon particles are heated at a temperature of about 220°

C., while being maintained under pressure.

13. A method as claimed in claim 7, wherein said polyvinyl alcohol is used in an amount of about 1 to about 5% by weight, based on the total weight of the adsorbent composition.

14. A method as claimed in claim 13, wherein said polyvinyl alcohol is used in an amount of about 2% by weight.

15. A method as claimed in claim 7, wherein the adsorbent thus obtained is subjected to a heat treatment at a temperature above the melting point of the polyvinyl alcohol to cause partial pyrolysis of said alcohol and evaporation of any solvent retained by said adsorbent.

16. A method as claimed in claim 15, wherein said heat treatment is carried out while holding the adsorbent under confinement to prevent swelling thereof.

17. A method as claimed in claim 15, wherein said polyvinyl alcohol has a melting point of about 200°

C. and wherein said heat treatment is carried out at a temperature of about 300°

C.

19. A dimensionally stable, high-density adsorbent comprising a compacted mass of high surface area carbon particles bound together with a binder and defining a network of substantially unobstructed micropores prepared according to the process of claim 1.

20. A high-density adsorbent as claimed in claim 19, wherein said binder is methylcellulose having a viscosity of about 4,000 centipoises, calculated as a 2% solution in water.

21. A high-density adsorbent as claimed in claim 20, wherein said methylcellulose is present in a proportion of about 10% by weight, based on the total weight of the adsorbent composition.

22. A high-density adsorbent as claimed in claim 19, wherein said binder is a polyvinyl alcohol having a molecular weight of about 125,000 and a melting point of about pb 200°

C.

23. A high-density adsorbent as claimed in claim 22, wherein said polyvinyl alcohol is present in a proportion of about 1 to about 5% by weight, based on the total weight of the adsorbent composition.

18. A method of producing a dimensionally stable, high-density adsorbent, comprising the steps of:

a) a mixing high surface area carbon particles in the form of a powder with a solution of a binder comprising a polyvinyl alcohol in a solvent to form a slurry and thereby wet each particle of carbon with the solution of binder;

b) removing the solvent from the slurry prepared in step (a) to obtain particles of carbon coated with a film of the binder; and

c) forming the binder coated particles of carbon into a shaped product by compacting the particles under a pressure of from about 140 MPa to about 600 MPa to cause binding of the carbon particles together without substantial obstruction of micropores defined in the particles, thereby obtaining an adsorbent capable of withstanding powdering when subjected to vibration and having a density substantially greater than that of the high surface area carbon in particulate form.