Hollow fiber carbon molecular sieve membrane and preparation and use thereof

• US 9,346,011 B2
• Filed: 04/29/2013
• Issued: 05/24/2016
• Est. Priority Date: 05/01/2012
• Status: Active Grant

• Current Assignee: Dow Global Technologies LLC (Dow, Inc.), Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Dow Global Technologies LLC (Dow, Inc.), Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Koros, William J., Xu, Liren, Brayden, Mark K., Martinez, Marcos V., Stears, Brien A.
• Primary Examiner(s): Greene, Jason M
• Application Number:
  US14/391,014
• Publication Number:
  US 20150053079A1
• Time in Patent Office: 1,121 Days
• Field of Search: 95/50
• US Class Current: 1/1
• CPC Class Codes: B01D 2323/08 Specific temperatures applied
• CPC Class Codes: B01D 2323/081 Heating
• CPC Class Codes: B01D 2323/22 Specific non-solvents or non-solvent system
• 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 67/0088 Physical treatment with compounds, e.g. swelling, coating or impregnation
• CPC Class Codes: B01D 67/0097 Storing or preservation
• CPC Class Codes: B01D 69/08 Hollow fibre membranes manufacture of hollow fibres D01D5/24, D01F1/08
• CPC Class Codes: B01D 69/087 Details relating to the spinning process
• CPC Class Codes: B01D 71/021 Carbon
• CPC Class Codes: B01D 71/42 Polymers of nitriles, e.g. polyacrylonitrile
• CPC Class Codes: B29C 48/022 characterised by the choice of material
• CPC Class Codes: B29D 22/00 Producing hollow articles tubular articles B29D23/00; pneumatic tyres B29D30/00
• CPC Class Codes: B29K 2023/00 Use of polyalkenes or derivatives thereof as moulding material
• CPC Class Codes: B29K 2091/00 Use of waxes as moulding material

Abstract

A hollow fiber carbon molecular sieve membrane, a process for preparing the hollow fiber carbon molecular sieve membrane, and a process for effecting separation of an olefin from a gaseous mixture that comprises the olefin in admixture with its corresponding paraffin and optionally one or more gaseous components selected from hydrogen, an olefin other than the olefin and a paraffin other than the corresponding paraffin. The process and membrane may also be used to effect separation of the olefin(s) from remaining feedstream components subsequent to an olefin-paraffin separation.

Claims

1. A process for separating an olefin from a gaseous mixture comprising the olefin admixed with its corresponding paraffin, the process comprising

flowing the gaseous mixture through a hollow fiber carbon molecular sieve, wherein the gaseous mixture is comprised of a first and second olefin, the first olefin having one less carbon than the second olefin, and their corresponding first and second paraffin and the hollow fiber carbon molecular sieve has a second olefin/first paraffin selectivity of at least 2.6 whereby the first and second olefin preferentially pass through the hollow fiber carbon molecular sieve forming a permeate gas and the first and second paraffin are preferentially retained forming a retentate gas, and

separating the retentate gas and permeate gas.

2. The process of claim 1, wherein the second olefin/first paraffin selectivity is at least 3.3.

3. The process of claim 2, wherein the two olefins are ethylene and propylene and the corresponding paraffins are ethane and propane.

4. The process of claim 1 wherein the gaseous mixture also comprises at least one additional gaseous component selected from a group consisting of acetylene, hydrogen, propadiene and methylacetylene and the conditions are sufficient to cause at least a portion of the additional gaseous component(s) and at least a portion of the olefin(s) to pass through the sieve while blocking passage of at least a portion of the corresponding paraffins through the sieve.

5. The process of claim 4, further comprising an additional step wherein gases that pass through the sieve are subjected to a second separation using either the same claim 1 hollow fiber carbon molecular sieve or a second claim 1 hollow fiber carbon molecular sieve, said second separation occurring under conditions sufficient to cause at least a portion of the additional gaseous component(s) to pass through the hollow fiber carbon molecular sieve while blocking passage of at least a portion of the olefin(s) through the hollow fiber carbon molecular sieve.

6. A process for preparing a hollow fiber carbon molecular sieve membrane, such process comprising a series of sequential steps:

a. Using a combination of spinning conditions, converting a spinning dope to a hollow fiber membrane, the spinning dope comprising from 15 percent by weight to 35percent by weight of a polyimide, from 20 percent by weight to 85 percent by weight of low volatility water soluble solvent, from 0 percent by weight to 10 percent by weight of non-volatile non-solvents, from 0 percent by weight to 40 percent by weight of volatile water soluble non-solvents, and from 0 percent by weight to 85 percent by weight of a volatile water soluble organic solvent, each weight percentage by weight being based upon total weight of the spinning dope and when added together for a spinning dope equal 100 percent by weight;

b. Pyrolyzing the hollow fiber membrane at a temperature within a range of from 450 degrees centigrade to 900 degrees centigrade using a purge gas that comprises an inert gas and oxygen, the oxygen being present in an amount of from greater than 0 moles per million moles of purge gas to less than or equal to 50 moles per million moles of purge gas, the purge gas flowing at a rate within a range of from 2 centimeters per minute to 100centimeters per minute;

c. Subjecting the pyrolized hollow fiber membrane to a post-pyrolysis treatment that comprises conditioning the pyrolyzed hollow fiber membrane in an atmosphere that is substantially free of water, water vapor, gaseous organic compounds and organic liquids for a period of time at least 72 hours after cooling from the final pyrolysis temperature to room temperature before exposure to feed gas, said combination of sequential steps yielding an olefin-paraffin hollow fiber carbon molecular sieve membrane that has an ethylene permeance at least 0.1 gas permeation units, a propylene permeance at least 0.1 gas permeation units, provided that the ethylene permeance is at least 2 times that of the ethane permeance and the propylene permeance is at least 4 times that of the propane permeance and further provided that propylene permeance is at least 1.5 times that of the ethane permeance.

7. The process of claim 6, wherein the combination of spinning conditions comprises a spinning dope flow rate per threadline within a range of from 50 to 500milliliters per hour, a bore fluid flow rate within a range of from 50 to 500 milliliters per hour, a spinneret temperature within a range of from 20 degrees centigrade to 90 degrees centigrade, a water quench temperature within a range of from 0 degrees centigrade to 65degrees centigrade, an air gap within a range of from 0.1 to 50 centimeters, and a fiber take-up rate within a range of from 1 to 100 meters per minute.

8. The process of claim 6 wherein the atmosphere of step c is comprised of a subatmospheric pressure within a range of from 0.1 Pascals to 2000 Pascals for a period of time at least 12 hours.

9. The process of claim 6, wherein pyrolysis step b comprises substeps as follows:

1). Heating the hollow fiber membrane to the temperature; and

2). Maintaining the heated hollow fiber membrane at the temperature for a period of time within a range of from 1 minute to 500 minutes.

10. The process of claim 9, wherein the temperature is within a range of from 500°

C. to 560°

C.

11. The process of claim 6, wherein the propylene permeance/ethane permeance is at least 20% greater to a hollow membrane that has not been subject to the post pyrolysis treatment.

12. The process of claim 6, wherein the polyimide is a 6FDA/BPDA-DAM polyimide.