Gas separation using organic-vapor-resistant membranes and PSA

• US 6,592,650 B2
• Filed: 03/25/2002
• Issued: 07/15/2003
• 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, Da Costa, Andre R., He, Zhenjie, Amo, Karl D.
• Primary Examiner(s): Spitzer, Robert H.
• Application Number:
  US10/105,923
• Publication Number:
  US 20030033929A1
• Time in Patent Office: 477 Days
• Field of Search: 95/45, 95/47--55, 95/96--06, 951/41, 951/43--47
• US Class Current: 95/47
• 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 71/522 Aromatic polyethers
• CPC Class Codes: B01D 71/64 Polyimides; Polyamide-imides; Polyester-imides; Polyamide acids or similar polyimide precursors

Abstract

A process for separating a gas from a gas mixture containing an organic compound gas or vapor by a hybrid separation combining adsorption with membrane gas separation, using membranes selective for the gas over the organic compound. The membranes use a selective layer made from a polymer having repeating units of a fluorinated cyclic structure of an at least 5-member ring, and demonstrate good resistance to plasticization by the organic components in the gas mixture under treatment.

Claims

1. A process for treating a gas mixture comprising a desired gas and an organic vapor, the process comprising the following steps:

(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 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;

(e) passing at least a portion of the permeate stream as a feed stream to an adsorption unit adapted to preferentially sorb the organic vapor;

(f) withdrawing from the adsorption unit a non-adsorbed product stream enriched in the desired gas compared to the gas mixture.

2. The process of claim 1, wherein the desired gas is selected from the group consisting of hydrogen, nitrogen, oxygen, methane and carbon dioxide.

3. The process of claim 1, wherein the organic vapor is selected from the group consisting of methane, ethylene, ethane and C₃₊ hydrocarbons.

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

5. The process of claim 1, wherein the gas mixture is selected from the group consisting of a natural gas stream, an associated gas stream, a refinery gas stream, a petrochemical plant gas stream, and an air stream.

6. The process of claim 1, wherein the desired gas is hydrogen and the organic vapor is a C₃₊ hydrocarbon.

7. The process of claim 1, wherein the permeate stream is compressed prior to step (e).

8. A process for treating a gas mixture comprising a desired gas and an organic vapor, the process comprising the following steps:

(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 the desired gas over the organic 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 organic 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;

(e) passing at least a portion of the permeate stream as a feed stream to an adsorption unit adapted to preferentially sorb the organic vapor;

(f) withdrawing from the adsorption unit a non-adsorbed product stream enriched in the desired gas compared to the gas mixture.

9. The process of claim 8, wherein the desired gas is selected from the group consisting of hydrogen, nitrogen, oxygen, methane and carbon dioxide.

10. The process of claim 8, wherein the organic vapor is selected from the group consisting of methane, ethylene, ethane and C₃₊ hydrocarbons.

11. The process of claim 8, wherein the polymer is formed from a monomer selected from the group consisting of fluorinated dioxoles, fluorinated dioxolanes, fluorinated cyclically polymerizable alkyl ethers and perfluorinated polyimides.

12. The process of claim 8, wherein the gas mixture is selected from the group consisting of a natural gas stream, an associated gas stream, a refinery gas stream, a petrochemical plant gas stream, and an air stream.

13. The process of claim 8, wherein the desired gas is hydrogen and the organic vapor is a C₃₊ hydrocarbon.

14. The process of claim 8, wherein the permeate stream is compressed prior to step (e).

15. A process for treating a gas mixture comprising a desired gas and an organic vapor, the process comprising the following steps:

(a) passing a gas mixture comprising a desired gas and an organic vapor into an adsorption unit adapted to preferentially sorb the organic vapor;

(b) withdrawing from the adsorption unit a non-adsorbed product stream enriched in the desired gas compared to the gas mixture;

(c) withdrawing from the adsorption unit a tail gas stream depleted in the desired gas compared to the gas mixture;

(d) bringing at least a portion of the tail gas stream into contact with the feed side of a separation membrane having a feed side and a permeate side, the 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;

(e) providing a driving force for transmembrane permeation;

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

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

16. The process of claim 15, wherein the desired gas is selected from the group consisting of hydrogen, nitrogen, oxygen, methane and carbon dioxide.

17. The process of claim 15, wherein the organic vapor is selected from the group consisting of methane, ethylene, ethane and C₃₊ hydrocarbons.

18. The process of claim 15, wherein the polymer is formed from a monomer selected from the group consisting of fluorinated dioxoles, fluorinated dioxolanes, fluorinated cyclically polymerizable alkyl ethers and perfluorinated polyimides.

19. The process of claim 15, wherein the gas mixture is selected from the group consisting of a natural gas stream, an associated gas stream, a refinery gas stream, a petrochemical plant gas stream, and an air stream.

20. The process of claim 15, wherein the desired gas is hydrogen and the organic vapor is a C₃₊ hydrocarbon.

21. The process of claim 15, wherein the tail gas stream is compressed prior to step (d).

22. A process for treating a gas mixture comprising a desired gas and an organic vapor, the process comprising the following steps:

(a) passing a gas mixture comprising a desired gas and an organic vapor into an adsorption unit adapted to preferentially sorb the organic vapor;

(b) withdrawing from the adsorption unit a non-adsorbed product stream enriched in the desired gas compared to the gas mixture;

(c) withdrawing from the adsorption unit a tail gas stream depleted in the desired gas compared to the gas mixture;

(d) bringing at least a portion of the tail gas stream into contact with the feed side of a separation membrane having a feed side and a permeate side, the 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 organic 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 organic vapor, as measured pre- and post-exposure with a test gas mixture of the same composition and under like conditions;

(e) providing a driving force for transmembrane permeation;

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

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

23. The process of claim 22, wherein the desired gas is selected from the group consisting of hydrogen, nitrogen, oxygen, methane and carbon dioxide.

24. The process of claim 22, wherein the organic vapor is selected from the group consisting of methane, ethylene, ethane and C₃₊ hydrocarbons.

25. The process of claim 22, wherein the polymer is formed from a monomer selected from the group consisting of fluorinated dioxoles, fluorinated dioxolanes, fluorinated cyclically polymerizable alkyl ethers and perfluorinated polyimides.

26. The process of claim 22, wherein the gas mixture is selected from the group consisting of a natural gas stream, an associated gas stream, a refinery gas stream, a petrochemical plant gas stream, and an air stream.

27. The process of claim 22, wherein the desired gas is hydrogen and the organic vapor is a C₃₊ hydrocarbon.

28. The process of claim 22, wherein the tail gas stream is compressed prior to step (d).