Hydrocarbon reverse osmosis membranes and separations

Patent metadata

Field	Value
Publication number	US-10456747-B2
Application number	US-201615347978-A
Country	US
Kind code	B2
Filing date	Nov 10, 2016
Priority date	Nov 13, 2015
Publication date	Oct 29, 2019
Grant date	Oct 29, 2019

Abstract

Asymmetric membrane structures are provided that are suitable for various types of separations, such as separations by reverse osmosis. Methods for making an asymmetric membrane structure are also provided. The membrane structure can include at least one polymer layer. Pyrolysis can be used to convert the polymer layer to a porous carbon structure with a higher ratio of carbon to hydrogen.

First claim

The invention claimed is:

1. A membrane structure comprising a first membrane layer and a second membrane layer, the first membrane layer having a pore volume of at least 0.2 cm 3 /g of pores with a median pore size of at least 20 nm, the second membrane layer comprising a porous carbon layer having a BET surface area of at least about 100 m 2 /g, the second membrane layer having a pore size distribution comprising a smallest substantial pore size peak having a median pore size of about 3.0 Angstroms to about 50 Angstroms.

2. The membrane structure of claim 1 , wherein the first membrane layer comprises a porous carbon layer.

3. The membrane structure of claim 1 , wherein the first membrane layer comprises a porous metal structure.

4. The membrane structure of claim 1 , wherein the second membrane layer has a pore size distribution comprising a smallest substantial pore size peak having a median pore size of about 3.0 Angstroms to about 10 Angstroms.

5. The membrane structure of claim 4 , wherein the smallest substantial pore size peak has a peak width at half of the peak height of about 1.0 Angstrom or less.

6. The membrane structure of claim 1 , wherein the second membrane layer has a BET surface area of at least about 300 m 2 /g.

7. The membrane structure of claim 1 , wherein the membrane structure comprises a hollow fiber membrane structure.

8. The membrane structure of claim 1 , wherein the second membrane layer has a thickness of about 3 microns or less.

9. The membrane structure of claim 1 , wherein the substantial pore size peak corresponding to the smallest median pore size has a median pore size when the membrane structure is exposed to a liquid for separation that differs by 10% or less from the median pore size when the membrane structure is not exposed to the liquid for separation, the liquid for separation comprising a solvent for a component for separation, the solvent comprising water, an alcohol that is a liquid at 25° C. and 100 kPa, a hydrocarbon that is a liquid at 25° C. and 100 kPa, or a combination thereof.

10. A membrane structure comprising a plurality of porous carbon membrane layers, the plurality of porous carbon layers including a first membrane layer and a second membrane layer, the first porous carbon membrane layer having a pore volume of at least 0.2 cm 3 /g of pores with a median pore size of at least 20 nm, the second porous carbon membrane layer having a BET surface area of at least about 300 m 2 /g, the second porous carbon membrane layer having a pore size distribution comprising a smallest substantial pore size peak having a median pore size of about 5.8 Angstroms to about 6.8 Angstroms.

11. A method for making a membrane structure, comprising:
forming a membrane structure comprising a first membrane layer and a second membrane layer, the first membrane layer comprising a pore volume of at least 0.02 cm 3 /g of pores with a median pore size of at least 20 nm, the second membrane layer comprising a BET surface area of less than 50 m 2 /g;
cross-linking the membrane structure to form a cross-linked membrane structure having a storage modulus of at least about 200 MPa at 100° C.;
pyrolyzing the cross-linked membrane structure at a pyrolysis temperature of about 450° C. to about 650° C. in a substantially inert atmosphere to form a pyrolyzed membrane structure, a first pyrolyzed membrane layer of the pyrolyzed membrane structure having a pore volume of at least 0.2 cm 3 /g of pores with a median pore size of at least 20 nm, a second pyrolyzed membrane layer of the pyrolyzed membrane structure comprising a porous carbon layer having a BET surface area of at least about 300 m 2 /g, the second pyrolyzed membrane layer of the pyrolyzed membrane structure having a pore size distribution comprising a smallest substantial pore size peak having a median pore size of about 3.0 Angstroms to about 50 Angstroms,
wherein the first membrane layer and the second membrane layer comprise a polyimide polymer, a partially fluorinated ethylene polymer, a partially fluorinated propylene polymer, a polyimide polymer, a polyamide-imide polymer, a polyetherimide polymer, or a combination thereof.

12. The method of claim 11 , wherein the second pyrolyzed membrane layer of the pyrolyzed membrane structure has a pore size distribution comprising a smallest substantial pore size peak having a median pore size of about 3.0 Angstroms to about 10 Angstroms.

13. The method of claim 11 , wherein the cross-linking comprises exposing the membrane structure to a methanol-based cross-linking solution; or wherein the cross-linking comprises exposing the membrane structure to p-xylylenediamine as a cross-linking agent; or a combination thereof.

14. The method of claim 11 , wherein the substantially inert atmosphere comprises about 50 vppm or less of O 2 .

15. The method of claim 11 , wherein the second pyrolyzed membrane layer of the pyrolyzed membrane structure has a thickness of about 3 microns or less.

16. The method of claim 11 , wherein the storage modulus is at least about 300 MPa at 100° C., or at least about 200 MPa at 200° C., or a combination thereof.

17. A method for making a membrane structure, comprising:
forming an extruded structure, cast structure, or combination thereof comprising a mixture of metal particles having a characteristic dimension of about 2.0 μm to about 5.0 μm and a binder;
calcining the extruded structure, cast structure, or combination thereof at a temperature of about 800° C. to about 1300° C. to form a first membrane layer comprising a porous metal structure having a pore volume of at least about 0.2 cm 3 /g of pores with a median pore size of at least about 20 nm;
forming a polymer layer on a surface of the porous metal structure; and
pyrolyzing the polymer layer at a pyrolysis temperature of about 450° C. to about 650° C. in a substantially inert atmosphere to form an asymmetric membrane structure comprising the pyrolyzed polymer layer, the pyrolyzed polymer layer comprising a porous carbon layer having a BET surface area of at least about 100 m 2 /g, the pyrolyzed polymer layer having a pore size distribution comprising a smallest substantial pore size peak having a median pore size of about 3.0 Angstroms to about 50 Angstroms.

18. The method of claim 17 , wherein the extruded structure, cast structure, or combination thereof comprises at least one of an extruded sheet and a hollow fiber.

19. The method of claim 17 , further comprising cross-linking the polymer layer to form a cross-linked polymer layer having a storage modulus of at least about 200 MPa at 100° C.

20. The method of claim 17 , wherein the polymer layer comprises a storage modulus of at least about 200 MPa at 100° C. prior to the pyrolyzing, the pyrolyzing being performed without prior cross-linking of the polymer layer.

21. The method of claim 17 , wherein the polymer layer comprises a polyimide polymer, a partially fluorinated ethylene polymer, a partially fluorinated propylene polymer, a polyimide polymer, a polyamide-imide polymer, a polyetherimide polymer, or a combination thereof.

22. The method of claim 17 , wherein the metal particles comprise stainless steel, nickel, chrome, copper, silver, gold, platinum, palladium, or a combination thereof.

23. The method of claim 17 , wherein the mixture of metal particles and binder comprises a weight ratio of metal particles to binder of about 0.5 to about 5.0.

24. A method for making a membrane struct

Assignees

• Mccool Benjamin A
• Deckman Harry W
• Lively Ryan P
• Koh Dong Yeun
• Exxonmobil Res & Eng Co
• Georgia Tech Res Inst

Inventors

• Mccool Benjamin A
• Deckman Harry W
• Lively Ryan P
• Koh Dong-Yeun

Classifications

• C07C7/005

  Processes comprising at least two steps in series · CPC title

• B01D69/08

  Hollow fibre membranes (manufacture of hollow fibres D01D5/24, D01F1/08) · CPC title

• B01D67/0067

  by carbonisation or pyrolysis · CPC title

• B01D61/007

  Separation by stereostructure, steric separation · CPC title

• C07C7/144

  using membranes, e.g. selective permeation · CPC title