Gas separation using C3+ hydrocarbon-resistant membranes

• US 6,361,582 B1
• Filed: 05/19/2000
• Issued: 03/26/2002
• Est. Priority Date: 05/19/2000
• Status: Expired due to Term

• Current Assignee: Membrane Technology and Research, Inc.
• Original Assignee: Membrane Technology and Research, Inc.
• Inventors: Pinnau, Ingo, Daniels, Ramin, Da Costa, Andre R., He, Zhenjie, Amo, Karl D.
• Primary Examiner(s): Spitzer, Robert H.
• Application Number:
  US09/574,303
• Time in Patent Office: 676 Days
• Field of Search: 95/45, 95/47--55, 96/4, 96/13, 96/14
• US Class Current: 95/45
• CPC Class Codes: B01D 53/228 characterised by specific membranes
• CPC Class Codes: B01D 69/02 characterised by their properties
• CPC Class Codes: B01D 71/32 containing fluorine atoms
• CPC Class Codes: B01D 71/643 Polyether-imides

Abstract

A process for separating a gas from a gas mixture containing the gas and a C₃₊ hydrocarbon vapor, using gas-separation membranes selective for the gas over the C₃₊ hydrocarbon vapor. The membranes use a selective layer made from a polymer having repeating units of a fluorinated polymer, and demonstrate good resistance to plasticization by the organic components in the gas mixture under treatment, and good recovery after exposure to liquid aromatic hydrocarbons.

Claims

1. A process for separating a desired gas from a gas mixture comprising the desired gas and a C₃₊ hydrocarbon vapor, the process comprising the steps of:

(a) passing the gas mixture across the feed side of a separation membrane having a feed side and a permeate side, the separation membrane having a selective layer comprising a polymer having;

(i) a ratio of fluorine to carbon atoms in the polymer greater than 1;

1;

(ii) a fractional free volume no greater than about 0.3; and

(iii) a glass transition temperature of at least about 100°

C.; and

the separation membrane being characterized by a post-exposure selectivity for the desired gas over the C₃₊ hydrocarbon vapor, after exposure of the separation membrane to liquid toluene and subsequent drying, that is at least about 65% of a pre-exposure selectivity for the desired gas over the C₃₊ hydrocarbon vapor, as measured pre- and post-exposure with a test gas mixture of the same composition and under like conditions;

(b) providing a driving force for transmembrane permeation;

(c) withdrawing from the permeate side a permeate stream enriched in the desired gas compared to the gas mixture;

(d) withdrawing from the feed side a residue stream depleted in the desired gas compared to the gas mixture.

2. The process of claim 1, wherein the desired gas is chosen from the group consisting of hydrogen, nitrogen, oxygen, argon, carbon dioxide and organic compounds.

3. The process of claim 1, wherein the desired gas is hydrogen.

4. The process of claim 1, wherein the desired gas is nitrogen.

5. The process of claim 1, wherein the desired gas is methane.

6. The process of claim 1, wherein the desired gas is carbon dioxide.

7. The process of claim 1, wherein the desired gas is propylene.

8. The process of claim 1, wherein the C₃₊ hydrocarbon vapor comprises a paraffin.

9. The process of claim 1, wherein the C₃₊ hydrocarbon vapor comprises an olefin.

10. The process of claim 1, wherein the C₃₊ hydrocarbon vapor comprises an aromatic compound.

11. The process of claim 1, wherein the C₃₊ hydrocarbon vapor is chosen from the group consisting of halogenated compounds, amines, ketones and alcohols.

12. The process of claim 1, wherein the gas mixture further comprises methane.

13. The process of claim 1, wherein the desired gas is nitrogen and the gas mixture further comprises methane.

14. The process of claim 1, wherein the selective layer comprises a perfluorinated polymer.

15. The process of claim 1, wherein the selective layer comprises a polymer formed from a fluorinated dioxole monomer.

16. The process of claim 1, wherein the selective layer comprises a polymer formed from a fluorinated dioxolane monomer.

17. The process of claim 1, wherein the selective layer comprises a polymer formed from a fluorinated cyclically polymerizable alkyl ether.

18. The process of claim 1, wherein the selective layer comprises a perfluorinated polyimide.

19. The process of claim 1, wherein the selective layer comprises a copolymer.

20. The process of claim 1, wherein the selective layer comprises a copolymer formed from fluorinated dioxole and tetrafluoroethylene repeat units.

21. The process of claim 1, wherein the polymer has the formula:

where x and y represent the relative proportions of the dioxole and the tetrafluoroethylene blocks, such that x+y=1.

22. The process of claim 1, wherein the selective layer comprises a polymer having the formula:

where n is a positive integer.

23. The process of claim 1, wherein the separation membrane is an integral asymmetric membrane.

24. The process of claim 1, wherein the separation membrane is a composite membrane comprising the selective layer supported on a microporous support membrane.

25. The process of claim 1, wherein the separation membrane comprises a composite membrane that comprises a support membrane, a gutter layer and the selective layer, the gutter layer forming a layer between the support membrane and the selective layer.

26. The process of claim 25, wherein the gutter layer comprises a copolymer of perfluoro-2,2-dimethyl-1,3-dioxole and tetrafluoroethylene.

27. The process of claim 1, wherein the gas mixture, as brought into contact with the feed side, has a total C₃₊ hydrocarbons partial pressure of at least about 25 psia.

28. The process of claim 1, wherein the gas mixture contains at least about 5% C₃₊ hydrocarbons.

29. The process of claim 1, wherein the gas mixture, as brought into contact with the feed side, has a pressure of at least about 30% of the saturation vapor pressure of the gas mixture.

30. The process of claim 1, wherein the post-exposure selectivity is at least about 70% of the pre-exposure selectivity.

31. A process for separating hydrogen from a gas mixture comprising hydrogen and a C₃₊ hydrocarbon vapor, the process comprising the steps of:

(a) passing the gas mixture across the feed side of a separation membrane having a feed side and a permeate side, the separation membrane having a selective layer comprising a polymer having;

(i) a ratio of fluorine to carbon atoms in the polymer greater than 1;

1;

(ii) a fractional free volume no greater than about 0.3; and

(iii) a glass transition temperature of at least about 100°

C.; and

the separation membrane being characterized by a post-exposure selectivity for hydrogen over the C₃₊ hydrocarbon vapor, after exposure of the separation membrane to liquid toluene and subsequent drying, that is at least about 65% of a pre-exposure selectivity for hydrogen over the C₃₊ hydrocarbon vapor, as measured pre- and post-exposure with a test gas mixture of the same composition and under like conditions;

(b) providing a driving force for transmembrane permeation;

(c) withdrawing from the permeate side a permeate stream enriched in hydrogen compared to the gas mixture;

(d) withdrawing from the feed side a residue stream depleted in hydrogen compared to the gas mixture.

32. The process of claim 31, wherein the selective layer comprises a polymer formed from a fluorinated monomer chosen from the group consisting of dioxoles, dioxolanes, alkyl ethers and perfluorinated polyimides.

33. The process of claim 31, wherein the selective layer comprises a copolymer formed from fluorinated dioxole and tetrafluoroethylene repeat units.

34. The process of claim 31, wherein the polymer has the formula:

where x and y represent the relative proportions of the dioxole and the tetrafluoroethylene blocks, such that x+y=1.

35. The process of claim 31, wherein the separation membrane comprises the selective layer supported on a microporous support membrane.

36. The process of claim 31, wherein the gas mixture further comprises methane.

37. The process of claim 31, wherein the separation membrane exhibits a mixed-gas selectivity for hydrogen over methane as measured at the operating conditions of the process of at least about 10.

38. The process of claim 31, wherein the separation membrane exhibits a mixed-gas selectivity for hydrogen over propane as measured at the operating conditions of the process of at least about 50.

39. The process of claim 31, wherein the gas mixture is a refinery off-gas stream.

40. The process of claim 31, wherein the post-exposure selectivity is at least about 70% of the pre-exposure selectivity.

41. A process for separating propylene from a gas mixture comprising propylene and propane, the process comprising the steps of:

(a) passing a gas mixture comprising propylene and propane across the feed side of a separation membrane having a feed side and a permeate side, the separation membrane having a selective layer comprising a polymer having;

(i) a ratio of fluorine to carbon atoms in the polymer greater than 1;

1;

(ii) a fractional free volume no greater than about 0.3; and

(iii) a glass transition temperature of at least about 100°

C.; and

the separation membrane being characterized by a post-exposure selectivity for propylene over propane, after exposure of the separation membrane to liquid toluene and subsequent drying, that is at least about 65% of a pre-exposure selectivity for propylene over propane as measured pre- and post-exposure with a test gas mixture of the same composition and under like conditions;

(b) providing a driving force for transmembrane permeation;

(c) withdrawing from the permeate side a permeate stream enriched in propylene compared to the gas mixture;

(d) withdrawing from the feed side a residue stream depleted in propylene compared to the gas mixture.

42. The process of claim 41, wherein the selective layer comprises a polymer formed from a fluorinated monomer chosen from the group consisting of dioxoles, dioxolanes, alkyl ethers and perfluorinated polyimides.

43. The process of claim 41, wherein the selective layer comprises a copolymer formed from fluorinated dioxole and tetrafluoroethylene repeat units.

44. The process of claim 41, wherein the polymer has the formula:

where x and y represent the relative proportions of the dioxole and the tetrafluoroethylene blocks, such that x+y=1.

45. The process of claim 41, wherein the separation membrane comprises the selective layer supported on a microporous support membrane.

46. The process of claim 41, wherein the separation membrane exhibits a mixed-gas selectivity for propylene over propane as measured at the operating conditions of the process of at least about 2.5.

47. The process of claim 41, wherein the post-exposure selectivity is at least about 70% of the pre-exposure selectivity.