Carbon Molecular Sieve Membrane (CMSM) Performance Tuning By Dual Temperature Secondary Oxygen Doping (DTSOD)

• US 20140000454A1
• Filed: 05/30/2013
• Published: 01/02/2014
• Est. Priority Date: 05/30/2012
• Status: Active Grant

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Koros, William John, Singh, Rachana
• Granted Patent: US 8,999,037 B2
• Time in Patent Office: Days
• US Class Current: 95/50
• CPC Class Codes: B01D 2256/10 Nitrogen
• CPC Class Codes: B01D 2256/12 Oxygen
• CPC Class Codes: B01D 2256/16 Hydrogen
• CPC Class Codes: B01D 2256/18 Noble gases
• CPC Class Codes: B01D 2256/22 Carbon dioxide
• CPC Class Codes: B01D 2256/245 Methane
• CPC Class Codes: B01D 2257/102 Nitrogen
• CPC Class Codes: B01D 2257/104 Oxygen
• CPC Class Codes: B01D 2257/108 Hydrogen
• CPC Class Codes: B01D 2257/11 Noble gases
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 2257/7025 Methane
• CPC Class Codes: B01D 53/228 characterised by specific membranes
• CPC Class Codes: B01D 63/00 Apparatus in general for separation processes using semi-permeable membranes
• CPC Class Codes: B01D 69/08 Hollow fibre membranes manufacture of hollow fibres D01D5/24, D01F1/08
• CPC Class Codes: C01B 13/0266 Carbon based materials
• CPC Class Codes: C01B 32/05 Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
• CPC Class Codes: Y02C 20/20 of methane
• CPC Class Codes: Y02C 20/40 of CO2
• CPC Class Codes: Y02P 20/151 Reduction of greenhouse gas [GHG] emissions, e.g. CO2
• CPC Class Codes: Y02P 20/156 : Methane [CH4]

Abstract

The various embodiments of the disclosure relate generally to carbon molecular sieve membranes (CMSM) and their associated fabrication processes, and more particularly to CMSM that maintain high gas selectivities without losing productivity. Methods for enriching a mixture of gases in one gas via the use of the CMS membranes, and gas enrichment devices using the same, are also disclosed.

Claims

1. A process for forming a carbon membrane comprising:

subjecting a polymer precursor membrane to a base pyrolysis temperature (BPT) in a very low oxygen environment (VLOE);

then

subjecting the polymer precursor membrane to a second temperature (SHT) step in a higher oxygen environment (HOE), wherein the second temperature is higher than the BPT

2. The process of claim 1, wherein the base pyrolysis temperature is between 400 and 500°

C.

3. The process of claim 1, wherein the second treatment step comprises a temperature of greater than or equal to 500°

C.

4. The process of claim 1, wherein the second treatment step comprises a temperature of greater than or equal to 525°

C.

5. The process of claim 1, wherein the second treatment step comprises a temperature of greater than or equal to 550°

C.

6. The process of claim 1, wherein the very low oxygen environment (VLOE) comprises less than 5 ppm oxygen.

7. The process of claim 1, wherein the very low oxygen environment (VLOE) comprises about 2 ppm or less oxygen.

8. The process of claim 1, wherein the very low oxygen environment (VLOE) comprises about 1 ppm or less oxygen.

9. The process of claim 1, wherein the higher oxygen environment comprises at least about 5 ppm oxygen.

10. The process of claim 1, wherein the higher oxygen environment comprises at least about 10 ppm oxygen.

11. The process of claim 1, wherein the higher oxygen environment comprises between about 5 ppm oxygen and about 60 ppm oxygen.

12. The process of claim 1, wherein the higher oxygen environment comprises between about 10 ppm oxygen and about 53 ppm oxygen.

13. The process of claim 1, wherein the polymer precursor membrane is a hollow fiber polymer precursor membrane.

14. The process of claim 1, wherein the polymer precursor membrane has a carbon content of at least 60 wt % and a hydrogen content of less than 5 wt. %.

15. A gas separation membrane comprising a carbon molecular sieve, wherein the gas separation membrane has an oxygen/nitrogen selectivity of greater than 7.1, and an oxygen permeance of at least about 13.8.

16. The gas separation membrane of claim 15, wherein the gas separation membrane has an oxygen/nitrogen selectivity of greater than 7.5.

17. The gas separation membrane of claim 15, wherein the gas separation membrane has an oxygen/nitrogen selectivity of greater than 8.

18. The gas separation membrane of claim 15, wherein the gas separation membrane has an oxygen permeance of greater than about 25.

19. The gas separation membrane of claim 15, wherein the gas separation membrane has an oxygen permeance of greater than about 30.

20. The gas separation membrane of claim 15, wherein the gas separation membrane has an oxygen/nitrogen selectivity of greater than 7.5 and an oxygen permeance of at least 30.

21. The gas separation membrane of claim 15, wherein the gas separation membrane has an oxygen/nitrogen selectivity of at least about 8.7 and an oxygen permeance of at least about 13.8.

22. The gas separation membrane of claim 15, wherein the gas separation membrane has an oxygen/nitrogen selectivity of at least about 8 and an oxygen permeance of at least about 30.

23. The gas separation membrane of claim 15, wherein the carbon molecular sieve comprises a pyrolyzed hollow fiber polymer precursor membrane.

24. A gas enrichment device, the device comprising

a gas stream inlet,

an enriched gas stream outlet,

a depleted gas stream outlet, and

a plurality of substantially aligned hollow carbon fibers,

wherein the hollow carbon fiber comprises a carbon molecular sieve having a oxygen/nitrogen selectivity of greater than 7.1 and an oxygen permeance of greater than 13.8.

25. A gas enrichment device of claim 24, wherein the hollow fiber carbon molecular sieve includes a bore or lumen passing through the length of the fiber, and a membrane on the outside of the fiber.

26. A gas enrichment device of claim 24, wherein the gas stream inlet is on the bore-side of the hollow fiber.

27. A gas enrichment device of claim 24, wherein the gas stream inlet is on the membrane-side of the hollow fiber.

28. A gas enrichment device of claim 24, wherein the membrane has an oxygen/nitrogen selectivity of greater than 7.5.

29. A gas enrichment device of claim 24, wherein the membrane has an oxygen/nitrogen selectivity of greater than 8.

30. A gas enrichment device of claim 24, wherein the membrane has an oxygen permeance of greater than 13.8.

31. A gas enrichment device of claim 24, wherein the membrane has an oxygen permeance of greater than 30.

32. A gas enrichment device of claim 24, wherein the membrane has an oxygen/nitrogen selectivity of greater than 8 and an oxygen permeance of at least 13.8.

33. A gas enrichment device of claim 24, wherein the membrane has an oxygen/nitrogen selectivity of at least about 8.7 and an oxygen permeance of at least about 13.8.

34. A method of decreasing the content of a gas in a mixture of gases, comprising

contacting the mixture with a gas separation membrane, and

separating two gas streams at the membrane,

wherein the gas separation membrane has an oxygen/nitrogen selectivity of at least 7.1 and a permeance of at least 13.8.

35. The method of claim 34, wherein the two gas streams comprise a first gas stream enriched in a first gas and a second gas stream that is depleted in the first gas.

36. The method of claim 34, wherein the gas separation membrane has an oxygen/nitrogen selectivity of greater than 7.5.

37. The method of claim 34, wherein the gas separation membrane has an oxygen/nitrogen selectivity of greater than 8.

38. The method of claim 34, wherein the gas separation membrane has an oxygen permeance of greater than 25.

39. The method of claim 34, wherein the gas mixture comprises a mixture containing oxygen and nitrogen, a mixture containing carbon dioxide and methane, a mixture containing helium and nitrogen, or a mixture containing helium and sulfur hexafluoride.

40. The method of claim 34, wherein the gas mixture is selected from a group consisting of oxygen/nitrogen, helium/sulfur hexafluoride, carbon dioxide/methane, ethylene/ethane, and propylene/propane.

41. The method of claim 34, wherein the gas mixture comprises oxygen and nitrogen.

42. A carbon molecular sieve prepared by a method comprising:

pyrolyzing a polymer precursor membrane in a first heat treatment in a very low oxygen environment; and

subjecting the pyrolyzed polymer precursor membrane in a second heat treatment in a higher oxygen environment, wherein the second heat treatment occurs at a temperature above the first heat treatment.

43. The carbon molecular sieve of claim 42, wherein the pyrolysis is conducted at between 400 and 500°

C.

44. The carbon molecular sieve of claim 42, wherein the very low oxygen environment comprises less than 5 ppm oxygen.

45. The carbon molecular sieve of claim 42, wherein the very low oxygen environment comprises about 2 ppm or less oxygen.

46. The carbon molecular sieve of claim 42, wherein the higher oxygen environment comprises at least about 5 ppm oxygen.

47. The carbon molecular sieve of claim 42, wherein the higher oxygen environment comprises at least about 10 ppm oxygen

48. The carbon molecular sieve of claim 42, wherein the carbon molecular sieve has an oxygen/nitrogen selectivity of greater than 7.1, and an oxygen permeance of at least about 13.8.

49. The carbon molecular sieve of claim 42, wherein the carbon molecular sieve has an oxygen/nitrogen selectivity of greater than 8, and an oxygen permeance of at least 13.8.