# US 11,992,814 B2 · Asymmetric modified carbon molecular sieve hollow fiber membranes having improved permeance

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- Number: US 11,992,814 B2
- Document ID: US11992814B2
- Status: Granted
- Kind: B2
- Application number: 17/407,465
- Filed: 2021-08-20
- Published: 2021-12-09
- Granted: 2024-05-28
- Earliest claimed: 2013-09-30
- Assignees: Georgia Tech Research Corporation; Air Liquide Advanced Technologies U.S. LLC
- Applicants: Georgia Tech Research Corporation; Air Liquide Advanced Technologies U.S., LLC
- Inventors: Nitesh Bhuwania; William John Koros; Paul Jason Williams
- Web page: https://patentgrep.com/patent/US11992814B2

## CPC

- B01D 71/021: {Carbon}
- B01D 53/228: {characterised by specific membranes}
- B01D 67/0067: {by carbonisation or pyrolysis}
- B01D 69/08: Hollow fibre membranes (manufacture of hollow fibres D01D5/24, D01F1/08)
- B01D 2323/12: Specific ratios of components used
- B01D 2325/20: Specific permeability or cut-off range
- Y02C 20/20: of methane
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- Y02C: CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]

## Abstract

The present invention provides an asymmetric modified CMS hollow fiber membrane having improved gas separation performance properties and a process for preparing an asymmetric modified CMS hollow fiber membrane having improved gas separation performance properties. The process comprises treating a polymeric precursor fiber with a solution containing a modifying agent prior to pyrolysis. The concentration of the modifying agent in the solution may be selected in order to obtain an asymmetric modified CMS hollow fiber membrane having a desired combination of gas permeance and selectivity properties. The treated precursor fiber is then pyrolyzed to form an asymmetric modified CMS hollow fiber membrane having improved gas permeance.

## Claims

### Claim 1

A process for preparing a thermally rearranged polymer material having improved gas separation performance properties comprising:
a. providing a polymer precursor material comprising a polyimide with an ortho-positioned functional group,
b. contacting the polymer precursor material with a solution comprising a modifying agent and a non-aqueous solvent, wherein the modifying agent is
a compound having the general formula R1R2R3R4Si, where each of R1, R2, R3, and R4 are independently C1-C6 alkyl or alkenyl, alkoxy, or halogen; with the proviso that the compound contains at least one C1-C6 alkyl or alkenyl substituent and at least one alkoxy or halogen substituent, or
a compound having the general formula R1R2R3R4M, where M is a metal and where each of R1, R2, R3, and R4 are independently C1-C6 alkyl or alkenyl, alkoxy, or halogen, with the proviso that the compound contains at least one C1-C6 alkyl or alkenyl substituent and at least one alkoxy or halogen substituent,
c. contacting the polymer precursor material of step b. with a moisture-containing atmosphere to form a treated polymer precursor material, and
d. heating the treated polymer precursor material to form a thermally rearranged polymer.

### Claim 2 (depends on 1)

The process of claim 1, wherein the modifying agent comprises between about 1 wt % and about 95 wt % of the solution.

### Claim 3 (depends on 2)

The process of claim 2, wherein the modifying agent comprises between about 1 wt % and about 50 wt % of the solution.

### Claim 4 (depends on 3)

The process of claim 3, wherein the modifying agent comprises between about 5 wt % and about 25 wt % of the solution.

### Claim 5 (depends on 1)

The process of claim 1, wherein the modifying agent is a compound having the general formula R1R2R3R4Si, where each of R1, R2, R3, and R4 are independently C1-C6 alkyl or alkenyl, alkoxy, or halogen; with the proviso that the compound contains at least one C1-C6 alkyl or alkenyl substituent and at least one alkoxy or halogen substituent.

### Claim 6 (depends on 5)

The process of claim 5, wherein the modifying agent is vinyl trimethoxy silane.

### Claim 7 (depends on 1)

The process of claim 1, wherein the modifying agent is a compound having the general formula R1R2R3R4M, where M is a metal and where each of R1, R2, R3, and R4 are independently C1-C6 alkyl or alkenyl, alkoxy, or halogen, with the proviso that the compound contains at least one C1-C6 alkyl or alkenyl substituent and at least one alkoxy or halogen substituent.

### Claim 8 (depends on 7)

The process of claim 7, where M is selected from the group consisting of Ge, B, Al, Ti, V, Fe, and combinations thereof.

### Claim 9 (depends on 1)

The process of claim 1, wherein the non-aqueous solvent comprises a C5 or greater, linear or branched-chain aliphatic hydrocarbon.

### Claim 10 (depends on 9)

The process of claim 9, wherein the C5 or greater linear or branched-chain aliphatic hydrocarbon is n-hexane.

### Claim 11 (depends on 1)

The process of claim 1, wherein the solution comprises vinyl trimethoxy silane and n-hexane.

### Claim 12 (depends on 1)

The process of claim 1, wherein the thermally rearranged polymer comprises polybenzoxazoles, polybenzothiazoles, polybenzimidazoles, or a combination thereof.

### Claim 13 (depends on 1)

The process of claim 1, wherein the treated polymer precursor material is heated to a temperature between about 250 and about 500° C. to form a thermally rearranged polymer.

### Claim 14 (depends on 13)

The process of claim 13, wherein the treated polymer precursor material is heated to a temperature between about 300 and about 450° C. to form a thermally rearranged polymer.

### Claim 15 (depends on 13)

The process of claim 13, wherein the treated polymer precursor material is heated under an inert atmosphere to form a thermally rearranged polymer.

### Claim 16 (depends on 1)

The process of claim 1, wherein the concentration of the modifying agent in the solution is selected to obtain a thermally rearranged polymer having a gas permeance property that is at least a 300% increase over an equivalent thermally rearranged polymer that is not subjected to the treatment of steps b. and c.

### Claim 17 (depends on 16)

The process of claim 16, wherein the concentration of the modifying agent in the solution is selected to obtain a thermally rearranged polymer having a selectivity that is at least 85% of the selectivity of an equivalent thermally rearranged polymer that is not subjected to the treatment of steps b. and c.

### Claim 18 (depends on 1)

The process of claim 1, wherein the concentration of the modifying agent in the solution is selected to obtain a thermally rearranged polymer that is useful for the separation of gases selected from the group consisting of CO2 and CH4, H2S and CH4, CO2/H2S and CH4, CO2 and N2, O2 and N2, N2 and CH4, He and CH4, H2 and CH4, H2 and C2H4, ethylene and ethane, propylene and propane, and ethane/propane and ethylene/propylene.

### Claim 19 (depends on 1)

The process of claim 1, wherein the concentration of the modifying agent in the solution is selected to obtain a thermally rearranged polymer that is useful for the separation of acid gases from a natural gas stream.

### Claim 20 (depends on 1)

The process of claim 1, wherein the concentration of the modifying agent in the solution is selected to obtain a thermally rearranged polymer that is useful for the separation of CO2 from a hydrocarbon-containing gas stream.