Nitrogen gas separation using organic-vapor-resistant membranes

• US 6,579,341 B2
• Filed: 03/18/2002
• Issued: 06/17/2003
• 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, Baker, Richard W., Da Costa, Andre R., He, Zhenjie, Amo, Karl D.
• Primary Examiner(s): Spitzer, Robert H.
• Application Number:
  US10/100,459
• Publication Number:
  US 20020170430A1
• Time in Patent Office: 456 Days
• Field of Search: 95/39, 95/41, 95/45, 95/47--55, 95/96--06
• US Class Current: 95/39
• 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 71/44 Polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds, not provided for in a single one of groups B01D71/26-B01D71/42
• CPC Class Codes: B01D 71/52 Polyethers
• CPC Class Codes: B01D 71/522 Aromatic polyethers
• CPC Class Codes: B01D 71/64 Polyimides; Polyamide-imides; Polyester-imides; Polyamide acids or similar polyimide precursors
• CPC Class Codes: Y02E 50/30 Fuel from waste, e.g. synthetic alcohol or diesel

Abstract

A process for separating nitrogen from a multicomponent gas mixture containing nitrogen and a hydrocarbon, such as natural gas or associated gas, using gas-separation membranes selective for nitrogen over the hydrocarbon. 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 nitrogen from a multicomponent gas mixture comprising nitrogen, a gaseous hydrocarbon and at least one other gaseous component, the process comprising the steps of:

(a) bringing the gas mixture into contact with 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 comprising repeating units having a fluorinated cyclic structure of an at least 5-member ring, the polymer having a fractional free volume no greater than about 0.3;

(b) providing a driving force for transmembrane permeation;

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

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

2. The process of claim 1, wherein the gaseous hydrocarbon is a C₃₊ hydrocarbon.

3. The process of claim 1, wherein the gaseous hydrocarbon is methane.

4. The process of claim 1, wherein the gaseous hydrocarbon is a light olefin.

5. The process of claim 1, wherein the gaseous hydrocarbon is chosen from the group consisting of halogenated compounds, amines, ketones and alcohols.

6. The process of claim 1, wherein the at least one other gaseous component is chosen from the group consisting of C₂₊ hydrocarbons, argon, oxygen, carbon dioxide, hydrogen sulfide, hydrogen and water vapor.

7. The process of claim 1, wherein the gas mixture is chosen from the group consisting of natural gas, associated gas, landfill gas, a gas stream from a petrochemical operation, and an off-gas stream from a process using a volatile organic compound.

8. The process of claim 1, wherein the polymer comprises a perfluorinated polymer.

9. The process of claim 1, wherein the polymer is formed from a monomer selected from the group consisting of fluorinated dioxoles, fluorinated dioxolanes and fluorinated cyclically polymerizable alkyl ethers.

10. The process of claim 1, wherein the polymer comprises a perfluorinated polyimide.

11. The process of claim 1, wherein the repeat unit is 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole.

12. The process of claim 1, wherein the polymer is a polyperfluoro (alkenyl vinyl ether).

13. The process of claim 1, wherein the polymer comprises a copolymer.

14. 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.

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

where n is a positive integer.

16. 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.

17. The process of claim 1, wherein the gas mixture is cooled before being brought into contact with the feed side.

18. The process of claim 1, wherein the gas stream is compressed prior to step (a).

19. The process of claim 1, wherein the separation membrane exhibits a mixed-gas selectivity for nitrogen over methane as measured at the operating conditions of the process of at least about 2.

20. The process of claim 1, wherein the separation membrane provides a pressure-normalized nitrogen flux when in use in the process of at least about 50 GPU.

21. The process of claim 1, wherein the gas mixture comprises at least about 10% nitrogen.

22. The process of claim 1, wherein the gas mixture comprises no more than about 10% nitrogen.

23. The process of claim 1, further comprising passing at least one of the gas mixture, the residue stream and the permeate stream to additional separation treatment.

24. The process of claim 1, wherein the gas mixture is associated gas from a flood operation and wherein at least a portion of the permeate stream is used as a reinjection gas for the flood operation.

25. The process of claim 1, wherein at least a portion of the residue stream is passed to a natural gas pipeline.

26. The process of claim 1, wherein the gas mixture is natural gas and the residue stream contains no more than about 6% nitrogen.

27. The process of claim 1, further comprising submitting the residue stream to a second membrane separation step.

28. The process of claim 1, further comprising removing a contaminant material that has been brought into a module housing the separation membrane during operation of steps (a) through (d) by:

(e) discontinuing steps (a) through (d); and

(f) flushing the module with an organic solvent.

29. A process for separating nitrogen from a multicomponent gas mixture comprising nitrogen, a gaseous hydrocarbon and at least one other gaseous component, the process comprising the steps of:

(a) bringing the gas mixture into contact with 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 nitrogen over the gaseous hydrocarbon, after exposure of the separation membrane to liquid toluene and subsequent drying, that is at least about 65% of a pre-exposure selectivity for nitrogen over the gaseous hydrocarbon, 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 nitrogen compared to the gas mixture;

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

30. The process of claim 29, wherein the gaseous hydrocarbon is a C₃₊ hydrocarbon.

31. The process of claim 29, wherein the gaseous hydrocarbon is methane.

32. The process of claim 29, wherein the gaseous hydrocarbon is a light olefin.

33. The process of claim 29, wherein the gaseous hydrocarbon is chosen from the group consisting of halogenated compounds, amines, ketones and alcohols.

34. The process of claim 29, wherein the at least one other gaseous component is chosen from the group consisting of C₂₊ hydrocarbons, argon, oxygen, carbon dioxide, hydrogen sulfide, hydrogen and water vapor.

35. The process of claim 29, wherein the gas mixture is chosen from the group consisting of natural gas, associated gas, landfill gas, a gas stream from a petrochemical operation, and an off-gas stream from a process using a volatile organic compound.

36. The process of claim 29, wherein the polymer comprises a perfluorinated polymer.

37. The process of claim 29, wherein the polymer is formed from a monomer selected from the group consisting of fluorinated dioxoles, fluorinated dioxolanes and fluorinated cyclically polymerizable alkyl ethers.

38. The process of claim 29, wherein the polymer comprises a perfluorinated polyimide.

39. The process of claim 29, wherein the repeat unit is 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole.

40. The process of claim 29, wherein the polymer is a polyperfluoro (alkenyl vinyl ether).

41. The process of claim 29, wherein the polymer comprises a copolymer.

42. The process of claim 29, 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.

43. The process of claim 29, wherein the polymer has the formula:

where n is a positive integer.

44. The process of claim 29, 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.

45. The process of claim 29, wherein the gas mixture is cooled before being brought into contact with the feed side.

46. The process of claim 29, wherein the gas stream is compressed prior to step (a).

47. The process of claim 29, wherein the separation membrane exhibits a mixed-gas selectivity for nitrogen over methane as measured at the operating conditions of the process of at least about 2.

48. The process of claim 29, wherein the separation membrane provides a pressure-normalized nitrogen flux when in use in the process of at least about 50 GPU.

49. The process of claim 29, wherein the gas mixture comprises at least about 10% nitrogen.

50. The process of claim 29, wherein the gas mixture comprises no more than about 10% nitrogen.

51. The process of claim 29, further comprising passing at least one of the gas mixture, the residue stream and the permeate stream to additional separation treatment.

52. The process of claim 29, wherein the gas mixture is associated gas from a flood operation and wherein at least a portion of the permeate stream is used as a reinjection gas for the flood operation.

53. The process of claim 29, wherein at least a portion of the residue stream is passed to a natural gas pipeline.

54. The process of claim 29, wherein the gas mixture is natural gas and the residue stream contains no more than about 6% nitrogen.

55. The process of claim 29, further comprising submitting the residue stream to a second membrane separation step.

56. The process of claim 29, further comprising removing a contaminant material that has been brought into a module housing the separation membrane during operation of steps (a) through (d) by:

(e) discontinuing steps (a) through (d); and

(f) flushing the module with an organic solvent.