Carbon molecular sieve for the kinetic separation of acid gases and fluorocarbons

• US 5,261,948 A
• Filed: 09/10/1992
• Issued: 11/16/1993
• Est. Priority Date: 09/10/1992
• Status: Expired due to Term

• Current Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.), University of Delaware
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.), University of Delaware
• Inventors: Manzer, Leo, Foley, Henry C., Mariwala, Ravindra K.
• Primary Examiner(s): SPITZER, ROBERT H
• Application Number:
  US07/943,433
• Time in Patent Office: 432 Days
• Field of Search: 55/71, 55/74, 55/75, 55/387, 55/389, 502/416, 502/420, 502/437
• US Class Current: 95/142
• CPC Class Codes: B01D 2253/102 Carbon
• CPC Class Codes: B01D 2253/308 Pore size
• CPC Class Codes: B01D 2256/26 Halogens or halogen compounds
• CPC Class Codes: B01D 53/02 by adsorption, e.g. preparative gas chromatography solid sorbent compositions B01J20/00, preparation of inorganic compounds or elements C01
• CPC Class Codes: B01D 53/72 Organic compounds not provided for in groups B01D53/48 - B01D53/70, e.g. hydrocarbons
• CPC Class Codes: B01J 20/20 comprising free carbon; comprising carbon obtained by carbonising processes
• CPC Class Codes: Y10S 95/903 Carbon

Abstract

A method for the preparation of a carbon molecular sieve capable of separating acid gases and fluorocarbons of the formula C_a H_b X_c F_d, wherein a is from 1 to about 6, b is from 0 to about 13, c is from 0 to about 13, d is from 1 to about 14, and X is a halogen; on the basis of shape selectivity and size exclusion. A precursor resin is heated at about 0.2° C. per minute to about 500° C. Then the resin is soaked at about 500° C. for about 6 hours in flowing inert gas.

Claims

1. A process for the preparation of a carbon molecular sieve capable of separating acid gases and fluorocarbons of the formula C_a H_b X_c F_d, wherein a is from 1 to about 6, is from 0 to about 13, c is from 0 to about 13, d is from 1 to about 14, and X is a halogen;

comprising the steps of;

a) heating an oxygen containing precursor resin at about 0.1°

to about 2°

C. per minute to about 400°

C. to about 800°

C. and

b) soaking to about 400°

C. to about 800°

C. for at least 1 hour in flowing inert gas.

2. A process as claimed in claim 1, wherein the carbon molecular sieve has a pore size of about 4.5 to about 5.5Å

.

3. A process as claimed in claim 1, wherein the precursor resin is selected from the group consisting of polyacrylonitrile, phenol formaldehyde resin, polyvinylidene chloride, polyfurfuryl alcohol and a mixture thereof.

4. A process as claimed in claim 1, wherein the precursor resin is polyfurfuryl alcohol.

5. A process as claimed in claim 1, wherein the fluorocarbon is CF₃ CH₂ F.

6. A process as claimed in claim 1, wherein the inert gas in helium.

7. A process as claimed in claim 1, wherein the steps a) and b) are

a) heating the precursor resin at about 0.1°

to about 2°

C. per minute to about 450°

C. to about 600°

C. and

b) soaking to about 450°

C. to about 600°

C. for about 4 to 6 hours in flowing inert gas.

8. A process as claimed in claim 1, wherein the steps a) and b) are

a) heating the precursor resin about 0.1°

to about 2°

C. per minute to about 500°

C. and

b) soaking to about 500°

C. for about 6 hours in flowing inert gas.

9. A process for the purification of CF₃ CH₂ F by the removal of HF in the azeotropic mixture, on the basis of shape selectivity and size exclusion comprising a bed of molecular sieving carbon prepared as in claim 1 which is contacted with the mixture at approximately 150°

-250°

C. and at 1 to 5 atm pressure and with a gas hourly space velocity between 100 and 1000.

10. A carbon molecular sieve made by the process of claim 1.

11. A carbon molecular sieve for the separation of acid gases from fluorocarbons said sieve comprising a precursor resin selected from the group consisting of polyacrylonitrile, phenol formaldehyde resin, polyvinylidene chloride, polyfurfuryl alcohol and a mixture thereof, and said sieve having a pore size of about 4.5 to about 5.5Å

, said fluorocarbons having the general formula C_a H_b X_c F_d wherein a is from 1 to about 6, b is from 0 to about 13, c is from 0 to about 13, and d is from 1 to about 14, and X is a halogen.

12. In a process for the separation of acid gases from fluorocarbons wherein the fluorocarbons have a general formula of C_a H_b X_c F_d wherein a is from 1 to about 6, b is from 0 to about 13, c is from 0 to about 13, and d is from 1 to about 14, and X is a halogen, the improvement being in the use of a carbon molecular sieve comprising an oxygen containing precursor resin and having a pore size of about 4.5 to 5.5Å

.

13. In the process as claimed in claim 12, wherein a is from 2 to about 4.

14. In the process as claimed in claim 12, wherein a is 2.

15. In the process as claimed in claim 12, wherein b is from 0 to about 6.

16. In the process as claimed in claim 12, wherein b is 2.

17. In the process as claimed in claim 12, wherien X is chlorine, fluorine or bromine.

18. In the process as claimed in claim 12, wherein X is chlorine.

19. In the process as claimed in claim 12, wherein c is from 0 to about 6.

20. In the process as claimed in claim 12, wherein c is 0.

21. In the process as claimed in claim 12, wherein d is from about 2 to about 6.

22. In the process as claimed in claim 12, wherein d is 4.