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Methods for enzyme-enhanced CO 2 capture include contacting a CO 2 -containing gas with an aqueous absorption solution at process conditions—such as high temperature, high pH, and/or using carbonate-based solutions—in the presence of Thermovibrio ammonificans carbonic anhydrase (TACA) or functional derivative thereof for catalyzing the hydration reaction of CO 2 into bicarbonate and hydrogen ions and/or catalyzing the desorption reaction to produce a CO 2 gas. The TACA may be provided to flow with the solution to cycle through a CO 2 capture system that includes an absorber and a stripper.
1. A method for absorbing CO 2 from a CO 2 -containing gas, the method comprising:
(a) in an absorber, contacting the CO 2 -containing gas with an aqueous absorption solution to dissolve the CO 2 into the aqueous absorption solution;
(b) providing a polypeptide having carbonic anhydrase activity that maintains at least 50% residual activity at 80° C. for 16 hours to catalyze the hydration reaction of the dissolved CO 2 into bicarbonate and hydrogen ions, wherein said polypeptide comprises an amino acid sequence having at least 70% sequence identity to SEQ ID NO: 6, wherein the SEQ ID NO: 6 is an amino acid sequence that lacks residues GGGAH (SEQ ID NO: 9) at a position corresponding to amino acid residues 2 to 6 of the wild-type Thermovibrio ammonificans carbonic anhydrase (TACA) sequence of SEQ ID NO: 4 resulting in an increased production level of said polypeptide as compared to the polypeptide of SEQ ID NO: 4, and
(c) generating a bicarbonate ion-containing absorption solution.
2. The method of claim 1 , further comprising
(d) treating the bicarbonate ion-containing absorption solution in a stripper to regenerate the absorption solution, wherein said treating comprises heating the absorption solution to provide conditions favorable to release CO 2 from the absorption solution, wherein the polypeptide of claim 1 catalyzes the dehydration reaction of bicarbonate ion into CO 2 ; and
(e) generating a regenerated absorption solution and a CO 2 gas.
3. The method of claim 2 , further comprising cooling the regenerated absorption solution.
4. The method of claim 2 , wherein the polypeptide retains at least 80% residual activity for at least 20 days when subjected to continuous temperature cycling conditions comprising repeatedly exposing a solution of 0.2 g/L of the polypeptide in 1.45 M K 2 CO 3 pH 10 from a 40° C. water bath to a 77° C. water bath for 4 minutes.
5. The method of claim 2 , wherein the polypeptide is subject to thermal cycling comprising temperature swings ranging from 25° C. to 105° C., when cycling from absorption to stripping,
wherein each thermal cycle comprises a temperature swing ranging from between 25° C. and 105° C., between 30° C. and 85° C., or between 40° C. and 60° C.
6. The method of claim 2 , wherein the temperature in the stripper is between 30 and 110° C.
7. The method of claim 1 , wherein the polypeptide is present in the absorption solution at a concentration ranges between 0.05 and 4 g/L.
8. The method of claim 1 , wherein the polypeptide is present in the absorption solution at a concentration ranges between 0.2 and 2 g/L.
9. The method of claim 1 , wherein the absorption solution comprises a monovalent metal carbonate.
10. The method of claim 9 , wherein the monovalent metal carbonate is sodium carbonate or potassium carbonate.
11. The method of claim 9 , wherein the monovalent metal carbonate is potassium carbonate present in the aqueous absorption solution at a concentration between about 1 M and about 2 M.
12. The method of claim 1 , wherein the pH of the aqueous absorption solution entering in the absorber is between about 8 and about 11.
13. The method of claim 1 , wherein the absorber is a packed column or a rotating packed bed (RPB).
14. The method of claim 1 , wherein the aqueous absorption solution comprises one or more absorption compounds selected from: a primary amine, a secondary amine, a tertiary amine, a primary alkanolamine, a secondary alkanolamine, a tertiary alkanolamine, a primary amino acid, a secondary amino acid, a tertiary amino acid, dialkylether of polyalkylene glycols, dialkylether or dimethylether of polyethylene glycol, an amino acid or a derivative thereof, monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), 2-(2-aminoethylamino)ethanol (AEE), 2-amino-2-hydroxymethyl-1,3-propanediol (Tris or AHPD), N-methyldiethanolamine (MDEA), dimethylmonoethanolamine (DMMEA), diethylmonoethanolamine (DEMEA), triisopropanolamine (TIPA), triethanolamine (TEA), diethanolamine (DEA), diisopropylamine (DIPA), methylmonoethanolamine (MMEA), tertiarybutylaminoethoxy ethanol (TBEE), N-2-hydroxyethyl-piperzine (HEP), 2-amino-2-hydroxymethyl-1,3-propanediol (AHPD), hindered diamine (HDA), bis-(tertiarybutylaminoethoxy)-ethane (BTEE), ethoxyethoxyethanol-tertiarybutylamine (EEETB), bis-(tertiarybutylaminoethyl)ether, 1,2-bis-(tertiarybutylaminoethoxy)ethane and/or bis-(2-isopropylaminopropyl)ether, piperazine or a derivative thereof, piperazine or derivative thereof substituted by at least one alkanol group, or any combination thereof.
15. The method of claim 14 , wherein the concentration of the absorption compound is between 0.1 and 8 M.
16. The method of claim 1 , wherein the temperature in the absorber is between 10 and 98° C.
17. The method of claim 1 , wherein the polypeptide is immobilized on a support.
18. The method of claim 1 , wherein the polypeptide is non-immobilized or dissolved in the aqueous absorption solution.
19. The method of claim 1 , wherein the CO 2 -containing gas is combustion gas comprising CO, NOx, and/or SOx.
20. The method of claim 1 , wherein the CO 2 -containing gas is biogas and/or raw petroleum gas, or is derived from natural gas combustion or coal combustion.