Mixed Amine and Non-Nucleophilic Base CO2 Scrubbing Process for Improved Adsorption at Increased Temperatures

• US 20120060686A1
• Filed: 09/09/2011
• Published: 03/15/2012
• Est. Priority Date: 09/09/2010
• Status: Active Grant

• Current Assignee: ExxonMobil Research & Engineering Company (Exxon Mobil Corporation)
• Original Assignee: ExxonMobil Research & Engineering Company (Exxon Mobil Corporation)
• Inventors: Kortunov, Pavel, Baugh, Lisa S., Calabro, David C., Siskin, Michael, Kamakoti, Preeti, Li, Quanchang
• Granted Patent: US 8,715,397 B2
• Time in Patent Office: Days
• US Class Current: 95/26
• CPC Class Codes: B01D 2252/20415 Tri- or polyamines
• CPC Class Codes: B01D 2252/20421 Primary amines
• CPC Class Codes: B01D 2252/20426 Secondary amines
• CPC Class Codes: B01D 2252/20431 Tertiary amines
• CPC Class Codes: B01D 2252/20478 Alkanolamines
• CPC Class Codes: B01D 2252/2056 Sulfur compounds, e.g. Sulfolane, thiols
• CPC Class Codes: B01D 2252/30 Ionic liquids and zwitter-ions
• CPC Class Codes: B01D 53/1475 Removing carbon dioxide
• CPC Class Codes: B01D 53/1493 Selection of liquid materials for use as absorbents
• CPC Class Codes: B01D 53/62 Carbon oxides
• CPC Class Codes: Y02C 20/40 of CO2

Abstract

A CO₂ amine scrubbing process uses an absorbent mixture combination of an amine CO₂ sorbent in combination with a non-nucleophilic, relatively stronger, typically nitrogenous, base. The weaker base(s) are nucleophilic and have the ability to react directly with the CO₂ in the gas stream while the relatively stronger bases act as non-nucleophilic promoters for the reaction between the CO₂ and the weaker base. The sorption and desorption temperatures can be varied by selection of the amine/base combination, permitting effective sorption temperatures of 70 to 90° C., favorable to scrubbing flue gas.

Claims

1. A cyclic process for separating CO₂ from a gas stream, which process comprises contacting the gas stream with an absorbent comprising an amine CO₂ sorbent and a non-nucleophilic base having a pK_a higher than that of the amine at a temperature above 50°

C. to sorb CO₂ and treating the absorbent containing the sorbed CO₂ under conditions sufficient to cause desorption of at least a portion of the CO₂.

2. The process of claim 1, wherein the amine sorbent comprises a primary amine, a secondary amine, or mixture thereof.

3. The process of claim 1, wherein the amine sorbent comprises a primary or secondary aliphatic, cycloaliphatic, or aromatic amine, or mixture thereof.

4. The process of claim 3, wherein the aliphatic amine comprises a primary amine selected from:

monoethanolamine, 2-amino-2-methyl-1-propanol, 2-(2-aminoethylamino)ethanol, 2-amino-2-hydroxymethyl-1,3-propanediol, diglycolamine, 2-ethoxyethylamine, 2-n-propoxyethylamine, 1,5-diamino-3-oxapentane, 3-aminopropionitrile, aminoacetonitrile, or hydroxyethylenediamine.

5. The process of claim 3, wherein the amine comprises a secondary amine selected from piperidine, piperazine, diethanolamine, diisopropanolamine, 1,5-bis(methylamino)-3-oxapentane, bis(2-methoxyethyl)amine, bis(2-ethoxyethyl)amine, ethoxyethanol tertiarybutylamine, or 3,3′

-iminodipropionitrile.

6. The process of claim 3, wherein the aliphatic amine comprises aniline.

7. The process of claim 1, wherein the non-nucleophilic base comprises an amine, an imine, an amidine, a guanidine, or a biguanide.

8. The process of claim 7, wherein the non-nucleophilic base has a pK_a of at least 8.5.

9. The process of claim 8, wherein the non-nucleophilic base has a pK_a of at least 9.

10. The process of claim 9, wherein the non-nucleophilic base has a pK_a of at least 10.

11. The process of claim 10, wherein the non-nucleophilic base has a pK_a of at least 13.

12. The process of claim 1, wherein the amine has a pK_a not greater than 11.5.

13. The process of claim 8, wherein the amine has a pK_a not greater than 11.5.

14. The process of claim 12, wherein the amine has a pK_a not greater than 10.

15. The process of claim 14, wherein the amine has a pK_a not greater than 9.

16. The process of claim 1, wherein the non-nucleophilic base has a pK_a of at least 3 units higher than that of the amine.

17. The process of claim 1, wherein the non-nucleophilic base has a pK_a of at least 7 units higher than that of the amine.

18. The process of claim 1, wherein the gas stream is contacted with the absorbent at a temperature of at least 70°

C. but not more than 100°

C.

19. The process of claim 18, wherein the gas stream is contacted with the absorbent at a temperature of at least 90°

C. but not more than 100°

C.

20. The process of claim 1, wherein the CO₂ is desorbed from the absorbent containing the sorbed CO₂ at a temperature of at least about 100°

C. to cause desorption of at least a portion of the sorbed CO₂.

21. The process of claim 15, wherein the CO₂ is desorbed from the absorbent containing the sorbed CO₂ at a temperature from 100 to 120°

C.

22. The process of claim 1, wherein the amine and the non-nucleophilic base are dissolved in a polar, aprotic solvent.

23. The process of claim 1, wherein the amine or the non-nucleophilic base is integrated onto a porous support.

24. The process of claim 1, wherein the amine and the non-nucleophilic base are integrated onto a porous support.

25. The process of claim 23, wherein the porous support is comprised of a material selected from carbon, alumina, silica, silica-alumina, magnesia, zeolites, and solid porous polymers.

26. The process of claim 24, wherein the porous support is comprised of a material selected from carbon, alumina, silica, silica-alumina, magnesia, zeolites, and solid porous polymers.

27. The process of claim 1, wherein the amine comprises a polyamine having both primary and secondary amine groups, having both secondary and tertiary amine groups, or having each of primary, secondary, and tertiary amine groups.