Removal of CO2, N2, or H2S from gas mixtures by swing adsorption with low mesoporosity adsorbent contactors

• US 20080282885A1
• Filed: 04/04/2008
• Published: 11/20/2008
• Est. Priority Date: 05/18/2007
• Status: Active Grant

• Current Assignee: ExxonMobil Research & Engineering Company (Exxon Mobil Corporation)
• Original Assignee: ExxonMobil Research & Engineering Company (Exxon Mobil Corporation)
• Inventors: Kelley, Bruce T., Chance, Ronald R., Northrop, Paul S., Corcoran, Edward W. JR., Thomas, Eugene R., DeMartin, Gregory J., Deckman, Harry W., Reyes, Sebastian C.
• Granted Patent: US 8,444,750 B2
• Time in Patent Office: Days
• US Class Current: 95/98
• CPC Class Codes: B01D 2253/108 Zeolites
• CPC Class Codes: B01D 2253/308 Pore size
• CPC Class Codes: B01D 2253/342 Monoliths
• CPC Class Codes: B01D 2256/24 Hydrocarbons
• CPC Class Codes: B01D 2257/102 Nitrogen
• CPC Class Codes: B01D 2257/304 Hydrogen sulfide
• CPC Class Codes: B01D 2257/504 Carbon dioxide
• CPC Class Codes: B01D 53/02 by adsorption, e.g. preparative gas chromatography solid sorbent compositions B01J20/00, preparation of inorganic compounds or elements C01
• CPC Class Codes: B01D 53/0423 Beds in columns
• CPC Class Codes: B01D 53/047 Pressure swing adsorption
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

The present invention relates to the separation of one or more of CO₂, N₂, and H₂S gas components from a gas mixture containing at least a second gas using a swing adsorption process unit. The adsorbent contactors of the swing adsorption process unit are engineered structured adsorbent contactors having a plurality of flow channels wherein 20 volume percent or less of the open pore volume of the contactors is in the mesopore and macropore range.

Claims

1. A process for removing a first gas component selected from the group consisting of CO₂, N₂, and H₂S from a gas mixture containing said first gas component and a second gas component, which process comprises:

a) conducting said gas mixture to a swing adsorption gas separation unit wherein the gas separation unit contains at least one adsorbent contactor comprised of;

i) a gas inlet end; and

ii) a gas outlet end;

wherein the gas inlet end and the gas outlet end are in fluid connection by a plurality of open flow channels wherein the surface of the open flow channels are comprised of an adsorbent material that has a selectivity for said first gas component over said second gas component of a gas mixture greater than 5, wherein the contactor has less than about 20% of its open pore volume in pores with diameters greater than about 20 angstroms and less than about 1 micron, and wherein at least a fraction of said first gas component is adsorbed into said adsorbent material, thereby resulting in a product stream depleted of said first gas component;

b) collecting said the product stream;

c) desorbing the adsorbed gas from said adsorbent material, thereby resulting in a waste gas stream rich in said first gas component; and

d) collecting said waste gas stream.

2. The process of claim 1 wherein the second gas component is CH₄ and the gas mixture is comprised of natural gas.

3. The process of claim 2 wherein greater than about 90% of the CH₄ in the gas mixture is recovered in the product stream.

4. The process of claim 1 wherein the adsorbent material is comprised of an 8-ring zeolite that has a Si to Al ratio of about 1:

1 to about 1000;

1.

5. The process of claim 4 wherein the 8-ring zeolite is DDR.

6. The process of claim 4 wherein the 8-ring zeolite is selected from Sigma-1 and ZSM-58.

7. The process of claim 5 wherein the 8-ring zeolites are in the form of zeolite crystals which are substantially uniform in size.

8. The process of claim 1 wherein the first gas is H₂S and the adsorbent material is comprised of a stannosilicate.

9. The process of claim 1 wherein the adsorbent contactor is comprised of a first adsorption zone comprising a first adsorbent material which is in fluid contact with a second adsorption zone comprising a second adsorbent material, wherein the composition of the first adsorbent material is different from the composition of a second adsorbent material.

10. The process of claim 9 wherein the first adsorbent material has a selectivity for the first gas component of a gas mixture over a second gas component of the gas mixture greater than 5;

the second adsorbent material has a selectivity for a third gas component over the second gas component of the gas mixture greater than 5; and

the second adsorbent material has a greater adsorption uptake for the third gas component than the first adsorbent material.

11. The process of claim 10 wherein the first gas component is CO₂, the second gas component is CH₄ and the third gas component is H₂S.

12. The process of claim 10 wherein the first gas component is N₂, the second gas component is CH₄ and the third gas component is H₂S.

13. The process of claim 10 wherein the first adsorbent material is comprised of an 8-ring zeolite that has a Si to Al ratio of about 1:

1 to about 1000;

1 and the second adsorbent material is comprised of a stannosilicate.

14. The process of claim 13 wherein the 8-ring zeolite is DDR.

15. The process of claim 13 wherein the 8-ring zeolite is selected from Sigma-1 and ZSM-58.

16. The process of claim 13 wherein the 8-ring zeolites are in the form of zeolite crystals which are substantially uniform in size.

17. The process of claim 1 wherein the adsorbent contactor has less than about 15% of its open pore volume in pores with diameters greater than about 20 angstroms and less than about 1 micron.

18. The process of claim 1 wherein adsorbent contactor contains an effective amount of a thermal mass material having a higher capacity or adsorbing heat than the adsorbent material.

19. The process of claim 1 wherein the adsorbent contactor contains both mesopores and macropores and wherein at least some of the mesopores and macropores are occupied with a blocking agent of an effective size so that it is small enough to fit into a mesopore but too large to fit into a micropore.

20. The process of claim 19 wherein the blocking agent is selected from the group consisting of polymers, microporous materials, solid hydrocarbons, and liquids.

21. The process of claim 1 wherein the adsorbent contactor is a parallel channel contactor.

22. The process of claim 21 wherein the gas mixture is comprised of natural gas containing CH₄ and greater than about 95% of the CH₄ in the gas mixture is recovered in the product stream.

23. The process of claim 21 wherein the adsorbent material is comprised of an 8-ring zeolite selected from DDR, Sigma-1, and ZSM-58 having a Si to Al ratio of about 1:

1 to about 1000;

1.

24. The process of claim 23 wherein the 8-ring zeolites are in the form of zeolite crystals which are substantially uniform in size.

25. The process of claim 21 wherein the adsorbent contactor is comprised of a first adsorption zone comprising a first adsorbent material which is in fluid contact with a second adsorption zone comprising a second adsorbent material, wherein the composition of the first adsorbent material is different from the composition of a second adsorbent material.

26. The process of claim 25 wherein the first adsorbent material has a selectivity for the first gas component of said natural gas stream over a second gas component of the gas mixture greater than 5;

the second adsorbent material has a selectivity for a third gas component over the second gas component of said natural gas stream greater than 5; and

the second adsorbent material has a greater adsorption uptake for the third gas component than the first adsorbent material.

27. The process of claim 26 wherein the first gas component is CO₂, the second gas component is CH₄ and the third gas component is H₂S.

28. The process of claim 26 wherein the first gas component is N₂, the second gas component is CH₄ and the third gas component is H₂S.

29. The process of claim 26 wherein the third gas component is H₂S and the second adsorbent material is comprised of a stannosilicate.

30. The process of claim 26 wherein the first adsorbent material is comprised of an 8-ring zeolite selected from DDR, Sigma-1, and ZSM-58 having a Si to Al ratio of about 1:

1 to about 1000;

1.

31. The process of claim 29 wherein the first adsorbent material is comprised of an 8-ring zeolite selected from DDR, Sigma-1, and ZSM-58 having a Si to Al ratio of about 1:

1 to about 1000;

1.

32. The process of claim 26 wherein the parallel channel contactor has less than about 15% of its open pore volume in pores with diameters greater than about 20 angstroms and less than about 1 micron.

33. The process of claim 32 wherein the parallel channel contactor is in the form selected from:

a) monolith comprised of a microporous adsorbent;

b) a monolith formed from a non-adsorbent material but whose channels are lined with a microporous adsorbent;

c) an array of hollow fibers comprised of a microporous adsorbent; and

d) laminated sheets having an upper and lower face both of which are comprised of a microporous adsorbent.

34. The process of claim 33 wherein the channel gap of the open flow channels is from about 5 to about 1000 microns.

35. The process of claim 33 wherein the ratio of adsorbent volume to open flow channel volume is from about 0.5:

1 to about 100;

1.