HOLLOW FIBER CARBON MOLECULAR SIEVE MEMBRANE AND PREPARATION AND USE THEREOF

• US 20150053079A1
• Filed: 04/29/2013
• Published: 02/26/2015
• 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., Brayden, Mark K., Stears, Brien A., Xu, Liren, Martinez, Marcos V.
• Granted Patent: US 9,346,011 B2
• Time in Patent Office: Days
• US Class Current: 95/50
• 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: 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. (canceled)

6. (canceled)

7. A process for effecting separation of an olefin from a gaseous mixture that comprises the olefin in admixture with its corresponding paraffins and optionally one or more gaseous components selected from hydrogen, an olefin other than the olefin and a paraffin other than the corresponding paraffin, which process comprises interposing a hollow fiber carbon molecular sieve in a flow of the gaseous mixture under conditions sufficient to cause at least a portion of the olefin to pass through the sieve while blocking passage of at least a portion of its corresponding paraffins through the sieve, the hollow fiber carbon molecular sieve being prepared by a process comprising a series of sequential steps as follows:

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 35 percent 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 100 centimeters 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.

2. The process of claim 7, wherein the combination of spinning conditions comprises a spinning dope flow rate per threadline within a range of from 50 to 500 milliliters 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 65 degrees 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.

3. The process of claim 7 wherein step c occurs under a subatmospheric pressure within a range of from 0.1 Pascals to 2000 Pascals and for a period of time at least 12 hours.

4. The process of claim 7, 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.

5. The process of claim 4, wherein the temperature is within a range of from 500°

C. to 560°

C.

8. The process of claim 7, wherein the gaseous mixture comprises at least two olefins and their corresponding paraffins, and the conditions are sufficient to cause at least a portion of each of the two olefins passes through the sieve while blocking passage of at least a portion of one of the corresponding paraffins through the sieve

9. The process of claim 8, wherein the two olefins are ethylene and propylene and the corresponding paraffins are ethane and propane.

10. The process of claim 7, 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.

11. The process of claim 10, further comprising an additional step wherein gases that pass through the sieve are subjected to a second separation using either the same claim 7 hollow fiber carbon molecular sieve or a second claim 7 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.