METHOD FOR PRODUCING CARBON MOLECULAR SIEVE MEMBRANES IN CONTROLLED ATMOSPHERES

• US 20110100211A1
• Filed: 06/17/2010
• Published: 05/05/2011
• Est. Priority Date: 10/29/2009
• Status: Active Grant

• Current Assignee: Air Liquide Advanced Technologies U.S. LLC (L'Air Liquide SA), Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Shell Oil Company (Shell Plc)
• Inventors: Kiyono, Mayumi, Koros, William John, Williams, Paul Jason
• Granted Patent: US 8,486,179 B2
• Time in Patent Office: Days
• US Class Current: 95/45
• CPC Class Codes: B01D 2256/245 Methane
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 2323/42 Details of membrane preparation apparatus
• CPC Class Codes: B01D 2325/021 Pore shapes
• CPC Class Codes: B01D 2325/022 Asymmetric membranes
• CPC Class Codes: B01D 53/22 by diffusion manufacturing semi-permeable membranes B01D67/00; form, structure or properties of semi-permeable membranes B01D69/00; material for semi-permeable membranes B01D71/00
• CPC Class Codes: B01D 53/228 characterised by specific membranes
• CPC Class Codes: B01D 63/02 Hollow fibre modules
• CPC Class Codes: B01D 67/0067 by carbonisation or pyrolysis
• CPC Class Codes: B01D 69/08 Hollow fibre membranes manufacture of hollow fibres D01D5/24, D01F1/08
• CPC Class Codes: B01D 71/021 Carbon
• CPC Class Codes: B01D 71/028 Molecular sieves carbon B01D71/021
• CPC Class Codes: Y02C 20/20 of methane
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

The invention concerns carbon molecular sieve membranes (“CMS membranes”), and more particularly the use of such membranes in gas separation. In particular, the present disclosure concerns an advantageous method for producing CMS membranes with desired selectivity and permeability properties. By controlling and selecting the oxygen concentration in the pyrolysis atmosphere used to produce CMS membranes, membrane selectivity and permeability can be adjusted. Additionally, oxygen concentration can be used in conjunction with pyrolysis temperature to further produce tuned or optimized CMS membranes.

Claims

1. A process for making a carbon membrane comprising the steps of:

a. providing a polymer precursor

b. heating said precursor in a chamber to at least a temperature at which pyrolysis byproducts are evolved; and

,

c. flowing an inert gas through said chamber during said heating step, said inert gas containing less than about 40 ppm of oxygen.

2. The process of claim 1, wherein said precursor is in the form of an asymmetric hollow polymer fiber.

3. The process of claim 1, wherein said inert gas contains less than about 10 ppm of oxygen.

7. The process of claim 1, wherein the inert purge gas contains argon, nitrogen, helium, or a combination thereof, and less than about 10 ppm of oxygen.

9. The process of claim 1, wherein the maximum temperature of pyrolysis is between about 450°

C. and about 800°

C.

10. The process of claim 1, wherein said precursor is heated at the maximum temperature for at least about one hour.

11. An asymmetric carbon molecule sieve hollow fiber module comprising

a sealable enclosure, said enclosure having;

a plurality of membranes contained therein, at least one of said membranes produced according to the process of claim 2;

an inlet for introducing a feed stream comprising natural gas;

an outlet for permitting egress of a permeate gas stream; and

,

another outlet for permitting egress of a retentate gas stream.

12. A process of separating acid gas components from a natural gas stream comprising:

providing an asymmetric carbon molecule sieve hollow fiber module according to claim 11;

introducing said natural gas stream into said module at a pressure of at least about 20 bar.

13. The process of claim 11, wherein said natural gas stream contains at least about 3% by volume of an acid gas component.

4. A process described in 1 where the polymer is a polyimide.

5. A process of claim 4 wherein the polymer precursor is formed from 5,5′

-[2,2,2-tri fluoro-1-(trifluoromethyl)ethylidene]bis-1,3-isobenzofurandione monomer.

6. A process of claim 4 wherein the polymer precursor is formed from an imide reaction product of 3,3′

,4,4′

-benzophenon tetracarboxylic dianhydride and diaminophenylidene.

8. The process of claim 4, wherein the inert purge gas contains argon, nitrogen, helium, or a combination thereof, and less than about 40 ppm of oxygen.

14. A process for reducing the concentration of acid gases in a natural gas stream comprising:

(a) providing a carbon membrane produced by a process including the steps of;

i. providing a membrane formed of asymmetric hollow polymer fibers;

ii. heating said membrane in a chamber to at least a temperature at which pyrolysis byproducts are evolved; and

,

iii. flowing an inert gas through said chamber, said inert gas containing less than about 40 ppm of oxygen,

(b) flowing said natural gas stream through said membrane to produce a retentate stream having a reduced concentration of acid gases.

15. The process of claim 14, wherein said inert gas contains less than about 10 ppm of oxygen.

16. A process for optimizing the CO₂/CH₄ selectivity of a carbon membrane comprising forming said carbon membrane by the steps of:

a. providing a polymer precursor in the form of asymmetric hollow polymer fibers;

b. heating said precursor in a chamber to at least a temperature at which pyrolysis byproducts are evolved; and

,

c. flowing an inert gas through said chamber during said heating step, said inert gas containing less than about 10 ppm of oxygen.

17. The process of claim 16, wherein said precursor is in the form of an asymmetric hollow polymer fiber.

18. A carbon membrane produced by the process of claim 16.

19. A process for making a carbon membrane having a predetermined degree of CO₂ permeability comprising:

a. providing a polymer precursor

b. heating said precursor in a chamber to at least a temperature at which pyrolysis byproducts are evolved; and

,

c. flowing a gas through said chamber during said heating step, the concentration of oxygen in said gas being selected to produce a carbon membrane having said predetermined degree of CO₂ permeability.

20. The process of claim 19, said oxygen concentration being selected to increase the permeability of said carbon membrane.

21. The process of claim 19, wherein said oxygen concentration is maintained between 1 ppm and about 30 ppm.

22. The process of claim 19 wherein the heating temperature is also selected to provide a predetermined degree of CO₂ permeability.

23. The process of claim 22 wherein the heating temperature is between about 450°

C. and about 600°

C.

24. The process of claim 22 wherein the heating temperature is between about 600°

C. and about 1000°

C.

25. A process according to claim 19, further comprising performing steps (a) through (c) an additional time, whereby a first carbon membrane having a first predetermined degree of CO₂ permeability is produced and a second carbon membrane having a second predetermined degree of CO₂ permeability is produced, said first and second predetermined degrees of CO₂ permeability differing by at least about 10 Barrer.

26. A process for making a carbon membrane having a predetermined degree of CO₂/CH₄ selectivity comprising the steps of:

a. providing a polymer precursor

b. heating said precursor in a chamber to at least a temperature at which pyrolysis byproducts are evolved; and

,

c. flowing a gas through said chamber during said heating step, the concentration of oxygen in said gas being selected to produce a carbon membrane having said predetermined degree of CO₂/CH₄ selectivity.

27. The process of claim 26, said oxygen concentration being selected to increase the CO₂/CH₄ selectivity of said carbon membrane.

28. The process of claim 26, wherein said oxygen concentration is maintained between 1 ppm and about 30 ppm.

29. The process of claim 26, wherein said oxygen concentration is maintained at between about 30 ppm and about 50 ppm.

30. The process of claim 26 wherein the heating temperature is also selected to provide a predetermined degree of CO₂/CH₄ selectivity.

31. The process of claim 30 wherein the heating temperature is between about 450°

C. and about 600°

C.

32. The process of claim 30 wherein the heating temperature is between about 600°

C. and about 1000°

C.

33. A process according to claim 26, further comprising performing steps (a) through (c) an additional time, whereby a first carbon membrane having a first predetermined degree of CO₂/CH₄ selectivity is produced and a second carbon membrane having a second predetermined degree of CO₂/CH₄ selectivity is produced, said first and second predetermined degrees of CO₂/CH₄ selectivity differing by at least about 10.

34. A gas separation apparatus, comprising one carbon membrane produced by pyrolyzing a polymer precursor in an atmosphere having a first oxygen concentration, and another carbon membrane produced by pyrolyzing a polymer precursor in an atmosphere having a second oxygen concentration, said first and second oxygen concentrations differing by at least 2 ppm oxygen to inert gas.

35. The apparatus of claim 34, wherein said first and second oxygen concentrations differ by at least about 10 ppm oxygen to inert gas.

36. The apparatus of claim 34, comprising one carbon membrane having a first CO₂ permeability, and another carbon membrane having a second CO₂ permeability, said first and second CO₂ permeabilities differing by at least about 10 Barrer.

37. The apparatus of claim 34 comprising one carbon membrane having a first CO₂/CH₄ selectivity, and another carbon membrane having a second CO₂/CH₄ selectivity, said first and second CO₂/CH₄ selectivities differing by at least about 10.

38. A process for making at least two carbon membranes having different predetermined degrees of CO₂ permeability comprising the steps of:

a. providing a first polymer precursor;

b. heating said first precursor in a first chamber to at least a temperature at which pyrolysis byproducts are evolved;

c. flowing a first gas through said first chamber during said first heating step, the concentration of oxygen in said first gas being selected to produce a first carbon membrane having a first predetermined degree of CO₂ permeability;

d. providing a second polymer precursor;

e. heating said second precursor in a second chamber to at least a temperature at which pyrolysis byproducts are evolved; and

f. flowing a second gas through said second chamber during said second heating step, the concentration of oxygen in said second gas being selected to produce a second carbon membrane having a second predetermined degree of CO₂ permeability,

wherein the concentration of oxygen in said first gas and said second gas differ by at least 2 ppm.

39. The first and second carbon membranes made by the process of claim 38.

40. A process for making at least two carbon membranes having different predetermined degrees of CO₂/CH₄ selectivity comprising the steps of:

a. providing a first polymer precursor;

b. heating said first precursor in a first chamber to at least a temperature at which pyrolysis byproducts are evolved;

c. flowing a first gas through said first chamber during said first heating step, the concentration of oxygen in said first gas being selected to produce a first carbon membrane having a first predetermined degree of CO₂/CH₄ selectivity;

d. providing a second polymer precursor;

e. heating said second precursor in a second chamber to at least a temperature at which pyrolysis byproducts are evolved; and

f. flowing a second gas through said second chamber during said second heating step, the concentration of oxygen in said second gas being selected to produce a second carbon membrane having a second predetermined degree of CO₂/CH₄ selectivity,

wherein the concentration of oxygen in said first gas and said second gas differ by at least 2 ppm.

41. The first and second carbon membranes made by the process of claim 40.