Stabilization of porous morphologies for high performance carbon molecular sieve hollow fiber membranes

• US 9,211,504 B2
• Filed: 11/01/2012
• Issued: 12/15/2015
• Est. Priority Date: 12/20/2011
• Status: Active Grant

• Current Assignee: Air Liquide Advanced Technologies U.S. LLC (L'Air Liquide SA)
• Original Assignee: Shell Oil Company (Shell Plc), Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Bhuwania, Nitesh, Koros, William John, Williams, Paul Jason
• Primary Examiner(s): Greene, Jason M
• Assistant Examiner(s): SHUMATE, ANTHONY R
• Application Number:
  US13/666,370
• Publication Number:
  US 20130152793A1
• Time in Patent Office: 1,139 Days
• Field of Search: 95/43, 95/45, 95/51, 96/4, 96/7, 96/8, 96/10, 96/14
• US Class Current: 1/1
• CPC Class Codes: B01D 2325/022 Asymmetric membranes
• CPC Class Codes: B01D 2325/20 Specific permeability or cut-off range
• CPC Class Codes: B01D 53/228 characterised by specific membranes
• CPC Class Codes: B01D 67/0067 by carbonisation or pyrolysis
• CPC Class Codes: B01D 67/0076 Pretreatment of inorganic membrane material prior to membrane formation, e.g. coating of metal powder
• 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: Y02C 20/40 of CO2

Abstract

Carbon molecular sieves (CMS) membranes having improved thermal and/or mechanical properties are disclosed herein. In one embodiment, a carbon molecular sieve membrane for separating a first and one or more second gases from a feed mixture of the first gas and one or more second gases comprises a hollow filamentary carbon core and a thermally stabilized polymer precursor disposed on at least an outer portion of the core. In some embodiments, the thermally stabilized polymer precursor is created by the process of placing in a reaction vessel the carbon molecular sieve membrane comprising an unmodified aromatic imide polymer, filling the reaction vessel with a modifying agent, and changing the temperature of the reaction vessel at a temperature ramp up rate and ramp down rate for a period of time so that the modifying agent alters the unmodified aromatic imide polymer to form a thermally stabilized polymer precursor.

Claims

1. A process for forming a carbon membrane using precursor pre-treatment comprising:

providing a polymer precursor;

pre-treating at least a portion of the polymer precursor with an agent that is capable of reducing substructure collapse; and

subjecting the pre-treated polymer precursor to pyrolysis;

wherein the step of pre-treating at least a portion of the polymer precursor provides at least a 300% increase in the CO₂ permeance of the carbon membrane in contrast to the carbon membrane without precursor pre-treatment.

2. The process of claim 1, wherein the step of pre-treating at least a portion of the polymer precursor provides at least a 400% increase in the CO₂ permeance of the carbon membrane in contrast to the carbon membrane without precursor pre-treating.

3. The process of claim 1, wherein the step of pre-treating at least a portion of the polymer precursor provides an increase in the gas separation selectivity of the carbon membrane in contrast to the carbon membrane without precursor pre-treatment.

4. The process of claim 3, wherein the gas separation selectivity comprises CO₂/CH₄ separation selectivity.

5. The process of claim 1, wherein the polymer precursor comprises a soluble thermoplastic polyimide.

6. The process of claim 1, wherein pre-treating at least a portion of the polymer precursor comprises chemically modifying the polymer precursor.

7. The process of claim 1, wherein the polymer precursor comprises an asymmetric hollow polymer fiber.

8. The process of claim 1, wherein the polymer precursor comprises an aromatic imide polymer precursor.

9. The process of claim 1, wherein the carbon membrane that is subject to the precursor pre-treatment has a similar selectivity to the carbon membrane without precursor pre-treatment.

10. A process for forming a carbon membrane by modifying at least a portion of the polymer precursor comprising:

providing a polymer precursor;

providing a modifying agent, the modifying agent comprising a silane having the formula R¹R²R³R⁴Si, where each of R¹, R², R³, and R⁴ is independently vinyl, C₁-C₆ alkyl, —

O-alkyl, or halide, with the proviso that the silane contain at least one vinyl group and at least one —

O-alkyl or halide;

contacting at least a portion of the modifying agent with the polymer precursor to provide for the modification of at least a portion of the polymer precursor; and

subjecting the modified polymer precursor to pyrolysis to form the carbon membrane;

wherein the modification of at least a portion of the polymer precursor increases the gas permeance of the carbon membrane relative to a carbon membrane formed from the polymer precursor which is not contacted with the modifying agent.

11. The process of claim 10, wherein the carbon membrane comprises a hollow fiber membrane.

12. The process of claim 11, wherein the hollow fiber membrane comprises an asymmetric membrane.

13. The process of claim 10, wherein the carbon membrane comprises a substantially non-collapsed, asymmetric hollow fiber membrane.

14. The process of claim 10, wherein the modifying agent is vinyl trimethoxy silane or vinyl triethoxy silane.

15. The process of claim 10 further comprising providing an initiator when contacting at least a portion of the modifying agent with the polymer precursor.

16. The process of claim 10, wherein the polymer precursor is an aromatic imide polymer.

17. The process of claim 10, wherein the polymer precursor is a composite structure comprising a first polymer supported on a porous second polymer.

18. The process of claim 12, wherein the asymmetric hollow fiber membrane comprises a group of membrane fibers that are in contact with one another during the pyrolysis process and do not adhere to one another after pyrolysis.

19. The process of claim 10, wherein the carbon membrane formed from a polymer precursor that is contacted with the modifying agent has a selectivity similar to that of a carbon membrane formed from the same polymer precursor which is not contacted with the modifying agent.

20. A process for making a carbon membrane comprising:

providing a polymer precursor comprising a soluble thermoplastic polyimide;

chemically modifying the polymer precursor with a modifying agent; and

heating the chemically modified precursor to at least a temperature at which pyrolysis byproducts are evolved;

wherein the carbon membrane has a CO₂ permeance (GPU) of greater than 35 and a CO₂/CH₄ selectivity greater than 88 in 100 psia in pure CO₂ and CH₄ gas streams at 35°

C.

21. The process of claim 20, wherein the modifying agent comprises vinyl trimethoxy silane or vinyl triethoxy silane.

22. A process for making a carbon membrane comprising:

providing a polymer precursor comprising a soluble thermoplastic polyimide;

chemically modifying the polymer precursor with a modifying agent; and

heating the chemically modified precursor to at least a temperature at which pyrolysis byproducts are evolved;

wherein the carbon membrane has a CO₂ permeance (GPU) of greater than 53 and a CO₂/CH₄ selectivity greater than 48 in 100 psia in pure CO₂ and CH₄ gas streams at 35°

C.

23. The process of claim 22, wherein the modifying agent comprises vinyl trimethoxy silane.

24. A process for forming a carbon membrane by modifying at least a portion of the polymer precursor comprising:

providing an aromatic imide polymer precursor;

providing a modifying agent;

contacting at least a portion of the modifying agent with the polymer precursor to provide for the modification of at least a portion of the polymer precursor; and

subjecting the modified polymer precursor to pyrolysis to form the carbon membrane;

wherein the modification of at least a portion of the polymer precursor increases the gas permeance of the carbon membrane relative to a carbon membrane formed from the polymer precursor which is not contacted with the modifying agent.

25. A process for forming a carbon membrane by modifying at least a portion of the polymer precursor comprising:

providing a polymer precursor;

providing a modifying agent;

contacting at least a portion of the modifying agent with the polymer precursor to provide for the modification of at least a portion of the polymer precursor; and

subjecting the modified polymer precursor to pyrolysis to form the carbon membrane;

wherein the modification of at least a portion of the polymer precursor increases the gas permeance of the carbon membrane relative to a carbon membrane formed from the polymer precursor which is not contacted with the modifying agent; and

wherein the carbon membrane comprises an asymmetric hollow fiber membrane, the asymmetric hollow fiber membrane comprising a group of fibers that are in contact with one another during the pyrolysis process and do not adhere to one another after pyrolysis.

26. A process for forming a carbon membrane using precursor pre-treatment comprising:

providing a polymer precursor;

pre-treating at least a portion of the polymer precursor with an agent that is capable of reducing substructure collapse; and

subjecting the pre-treated polymer precursor to pyrolysis;

wherein the step of pre-treating at least a portion of the polymer precursor provides at least a 300% increase in the gas permeance of the carbon membrane in contrast to the carbon membrane without precursor pre-treatment; and

wherein pre-treating at least a portion of the polymer precursor comprises chemically modifying the polymer precursor.

27. The process of claim 26, wherein the step of pre-treating at least a portion of the polymer precursor provides at least a 400% increase in the gas permeance of the carbon membrane in contrast to the carbon membrane without precursor pre-treating.

28. The process of claim 26, wherein the polymer precursor comprises an asymmetric hollow polymer fiber.

29. The process of claim 26, wherein the polymer precursor comprises an aromatic imide polymer precursor.

30. The process of claim 26, wherein the step of pre-treating at least a portion of the polymer precursor provides an increase in the gas separation selectivity of the carbon membrane in contrast to the carbon membrane without precursor pre-treatment.

31. The process of claim 26, wherein the carbon membrane that is subject to the precursor pre-treatment has a similar selectivity to the carbon membrane without precursor pre-treatment.