Carbon dioxide removal and ionic liquid compounds useful therein
View Patent ↗This invention relates to compounds useful as ionic liquids that are based on an N-substituted pyrrolidinone and incorporate a pendant ammonium cation that is spaced from the pyrrolidone ring by a variable length linker; and to methods of carbon dioxide removal in which they may be used.
1. A method for the removal of CO 2 from a gaseous mixture comprising contacting the gaseous mixture with one or more compounds represented by the structure of the following Formula I:
wherein
(a) Z is —(CH 2 ) n —, wherein n is an integer from 2 to 12, or Z is —[(CH 2 ) b —O] c —(CH 2 ) d — wherein b and d are each independently integers from 1 to 4, and c is an integer from 1 to 8;
(b) R 2 and R 3 are each independently H or a C 1 to C 6 straight-chain or branched alkyl group;
(c) R 4 is H, a C i to C 6 straight-chain or branched alkyl group, or —[(CH 2 ) p —X] q —(CH 2 ) r —Y—R 6 wherein X and Y are each independently O or NR 6 , p and r are each independently an integer from 1 to 4, q is an integer from 0 to 8, and R 6 is H or a C 1 to C 6 straight-chain or branched alkyl group; and
(d) A − is an anion selected from the members of the group consisting of levulinate, [BF 4 ] − , [PF 6 ] − , [SbF 6 ] − , [CH 3 CO 2 ] − , [HSO 4 ] − , [CF 3 SO 3 ] − , [HCF 2 CF 2 SO 3 ] − , [CF 3 HFCCF 2 SO 3 ] − , [CF 3 —O—CFHCF 2 SO 3 ] − , [CF 3 CF 2 OCFHCF 2 SO 3 ] − , [CF 3 CF 2 CF 2 OCFHCF 2 SO 3 ] − , [HCClFCF 2 SO 3 ] − , [(CF 3 SO 2 ) 2 N] − , [AlCl 4 ] − , [CF 3 CO 2 ] − , [NO 3 ] − , [SO 4 ] 2− , Cl − , Br − , I − , and F − .
2. The method of claim 1 wherein Z is —(CH 2 ) n —.
3. The method of claim 2 wherein n is an integer from 2 to 6.
4. The method of claim 2 wherein n is 2.
5. The method of claim 1 wherein R 4 is H, C 1 to C 6 straight-chain or branched monovalent alkyl.
6. The method of claim 5 wherein R 2 , R 3 and R 4 taken independently are H, —CH 3 , —CH 2 CH 3 , or —CH 2 CH 2 CH 3 .
7. The method of claim 1 wherein A − is levulinate.
8. The method of claim 1 wherein A − is selected from the members of the group consisting of [BF 4 ] − , [PF 6 ] − , [SbF 6 ] − , [CH 3 CO 2 ] − , [HSO 4 ] − , [CF 3 SO 3 ] − , [HCF 2 CF 2 SO 3 ] − , [CF 3 HFCCF 2 SO 3 ] − , [CF 3 —O—CFHCF 2 SO 3 ] − , [CF 3 CF 2 OCFHCF 2 SO 3 ] − , [CF 3 CF 2 CF 2 OCFHCF 2 SO 3 ] − , [HCClFCF 2 SO 3 ] − , [(CF 3 SO 2 ) 2 N] − , [AlCl 4 ] − , [CF 3 CO 2 ] − , [NO 3 ] − , [SO 4 ] 2− , Cl − , Br − , I − , and F − .
9. The method of claim 1 wherein Z is —[(CH 2 ) b —O] c —(CH 2 ) d —.
10. The method of claim 9 wherein c is 1, and b and d are 2.
11. The method of claim 9 wherein c is 2, and b and d are 2.
12. The method of claim 1 wherein R 4 is —[(CH 2 ) p —X] q —(CH 2 ) r —Y—R 6 .
13. The method of claim 12 wherein X and Y are O.
14. The method of claim 12 wherein X and Y are NR 6 .
15. The method of claim 12 wherein r and p are 2 to 4.
16. The method of claim 12 wherein r and p are 2.
17. The method of claim 12 wherein q is 0 to 4.
18. The method of claim 12 wherein R 4 is —(CH 2 ) 2 —O—(C 2 H 5 ), —(CH 2 ) 2 —O—(CH 3 ), or —(CH 2 ) 2 —OH.
19. The method of claim 1 wherein the removal of CO2 from the gaseous mixture occurs in a removal apparatus; wherein, in the removal apparatus, CO 2 is dissolved into a Formula (I) compound(s) to form (i) a purified fraction that is depleted in CO 2 content and (ii) a solvent fraction that is enriched in CO 2 content; and wherein the solvent fraction is separated from the removal apparatus.
20. The method of claim 19 wherein CO 2 is separated from the solvent fraction to form a rectified solvent fraction, and the rectified solvent fraction is returned to the removal apparatus.