PROCESS FOR PRODUCING CARBON MEMBRANES

• US 20120079944A1
• Filed: 09/30/2011
• Published: 04/05/2012
• Est. Priority Date: 10/01/2010
• Status: Active Grant

• Current Assignee: BASF SE
• Original Assignee: BASF SE
• Inventors: Therre, Jörg, VOß, Hartwig
• Granted Patent: US 8,608,828 B2
• Time in Patent Office: Days
• US Class Current: 96/11
• CPC Class Codes: B01D 2256/16 Hydrogen
• CPC Class Codes: B01D 2256/24 Hydrocarbons
• CPC Class Codes: B01D 2257/108 Hydrogen
• CPC Class Codes: B01D 2257/11 Noble gases
• CPC Class Codes: B01D 2257/406 Ammonia
• CPC Class Codes: B01D 2257/7022 Aliphatic hydrocarbons
• CPC Class Codes: B01D 2257/7025 Methane
• CPC Class Codes: B01D 2257/80 Water
• CPC Class Codes: B01D 2323/08 Specific temperatures applied
• CPC Class Codes: B01D 2323/081 Heating
• CPC Class Codes: B01D 2323/30 Cross-linking
• CPC Class Codes: B01D 2325/022 Asymmetric membranes
• CPC Class Codes: B01D 53/228 characterised by specific membranes
• CPC Class Codes: B01D 67/0048 by sol-gel transition
• CPC Class Codes: B01D 67/0067 by carbonisation or pyrolysis
• CPC Class Codes: B01D 67/0095 Drying
• CPC Class Codes: B01D 69/10 Supported membranes; Membrane supports
• CPC Class Codes: B01D 71/021 Carbon
• CPC Class Codes: Y02C 20/20 of methane

Abstract

There is described a process for producing carbon membranes suitable for gas separation, comprising the steps of:

• a) coating a porous substrate with a solution of at least one organic polymer which can be converted to a carbon membrane by pyrolysis,
• b) drying the polymer coating on the porous substrate by removing the solvent,
• c) pyrolyzing the polymer coating on the porous substrate to form the carbon membrane suitable for gas separation,

it being possible to conduct any of steps a) to c) or the sequence of steps a) to c) more than once, and the pyrolysis in step c) being effected at a temperature higher than the baking temperature of the porous substrate.

Claims

1. A process for producing carbon membranes suitable for gas separation, comprising the steps of:

a) coating a porous substrate with a solution of at least one organic polymer which can be converted to a carbon membrane by pyrolysis,

b) drying the polymer coating on the porous substrate by removing the solvent,

c) pyrolyzing the polymer coating on the porous substrate to form the carbon membrane suitable for gas separation,

it being possible to conduct any of steps a) to c) or the sequence of steps a) to c) more than once, and the pyrolysis in step c) being effected at a temperature higher than the baking temperature of the porous substrate.

2. The process according to claim 1, wherein the porous substrate has a surface mesoporous ceramic oxide layer atop a substrate carrier layer, said surface mesoporous ceramic oxide layer having a baking temperature below the pyrolysis temperature of the organic polymer.

3. The process according to claim 2, wherein the surface mesoporous ceramic oxide layer has a mean pore diameter in the range from 2 to 10 nm.

4. The process according to claim 2, wherein the substrate carrier layer is selected from porous metals, porous ceramics, porous glasses and porous composites thereof.

5. The process according to claim 2, wherein the surface mesoporous ceramic oxide layer has been produced by a sol-gel technique.

6. The process according to claim 2, wherein the surface mesoporous ceramic oxide layer is formed from TiO₂, ZrO₂, Al₂O₃, SiO₂ or mixtures thereof.

7. The process according to claim 6, wherein the surface mesoporous ceramic oxide layer has been formed from γ

-Al₂O₃.

8. The process according to claim 1, wherein the surface mesoporous ceramic oxide layer in unbaked form is coated with the solution of the at least one organic polymer.

9. The process according to claim 1, wherein the pyrolysis in step c) is performed at temperatures in the range from 500 to 900°

C., preferably at temperatures up to 500°

C. under nitrogen and above 500°

C. under argon.

10. The process according to claim 1, wherein the at least one organic polymer is selected from cellulose, polymeric phenolic resins, melamine resins, urea resins, furan resins, polyimide resins, epoxy resins, polyfurfuryl alcohol, polyvinyl chloride, polyacrylonitrile, polyethylene, ethylenically unsaturated polyesters and mixtures thereof.

11. The process according to claim 10, wherein the ethylenically unsaturated polyester has repeat units of aliphatic diols, aromatic dicarboxylic acids and ethylenically unsaturated dicarboxylic acids.

12. The process according to claim 11, wherein the aliphatic diols are C_2-12-alkanediols and the ethylenically unsaturated dicarboxylic acid is maleic acid.

13. The process according to claim 10, wherein the solution of ethylenically unsaturated polyesters additionally comprises a crosslinking ethylenically unsaturated monomer and a free-radical former as a crosslinking initiator.

14. The process according to claim 13, wherein the crosslinking ethylenically unsaturated monomer is styrene or α

-methylstyrene.

15. A carbon membrane obtainable by a process according to claim 1.