Phosphonium-based ionic liquids and their use in the capture of polluting gases

1. An ionic liquid composition having the following chemical structural formula:

wherein R 1 , R 2 , R 3 , and R 4 are independently selected from hydrocarbon groups containing at least 1 and up to 20 carbon atoms, wherein at least one of R 1 , R 2 , R 3 , and R 4 is an alkyl or alkenyl group, provided that at least one of R 1 , R 2 , R 3 , and R 4 contains at least four more carbon atoms than another of R 1 , R 2 , R 3 , and R 4 ; and X − is a deprotonated phenolic or thiophenolic anion reactive with carbon dioxide or sulfur dioxide.

2. The ionic liquid composition of claim 1 , wherein R 1 , R 2 , R 3 , and R 4 contain at least 3 and up to 20 carbon atoms.

3. The ionic liquid composition of claim 1 , wherein R 1 , R 2 , R 3 , and R 4 contain at least 4 and up to 20 carbon atoms.

4. The ionic liquid composition of claim 1 , wherein R 1 , R 2 , R 3 , and R 4 contain at least 5 and up to 20 carbon atoms.

5. The ionic liquid composition of claim 1 , wherein R 1 , R 2 , R 3 , and R 4 contain at least 6 and up to 20 carbon atoms.

6. The ionic liquid composition of claim 1 , wherein at least two of R 1 , R 2 , R 3 , and R 4 are alkyl groups.

7. The ionic liquid composition of claim 1 , wherein said hydrocarbon groups are alkyl groups.

8. The ionic liquid composition of claim 1 , wherein at least two of R 1 , R 2 , R 3 , and R 4 are not equivalent.

9. The ionic liquid composition of claim 1 , wherein at least one of R 1 , R 2 , R 3 , and R 4 contains at least five more carbon atoms than another of R 1 , R 2 , R 3 , and R 4 .

10. The ionic liquid composition of claim 1 , wherein at least one of R 1 , R 2 , R 3 , and R 4 contains at least six more carbon atoms than another of R 1 , R 2 , R 3 , and R 4 .

11. The ionic liquid composition of claim 1 , wherein said deprotonated phenolic or thiophenolic anion does not possess a carboxylate substituent.

12. The ionic liquid composition of claim 1 , wherein said deprotonated phenolic or thiophenolic anion is not an amino acid.

13. The ionic liquid composition of claim 1 , wherein said ionic liquid possesses a viscosity of no more than 2000 cP at 25° C.

14. The ionic liquid composition of claim 1 , wherein said ionic liquid possesses a viscosity of no more than 1500 cP at 25° C.

15. The ionic liquid composition of claim 1 , wherein said ionic liquid possesses a viscosity of no more than 1000 cP at 25° C.

16. The ionic liquid composition of claim 1 , wherein said ionic liquid possesses a decomposition temperature of at least 150° C.

17. The ionic liquid composition of claim 1 , wherein said ionic liquid possesses a CO 2 absorption capacity of at least 0.7 moles CO 2 per mole of ionic liquid.

18. The ionic liquid composition of claim 1 , wherein said ionic liquid possesses a CO 2 absorption capacity of at least 0.8 moles CO 2 per mole of ionic liquid.

19. The ionic liquid composition of claim 1 , wherein said ionic liquid possesses a CO 2 absorption capacity of at least 0.9 moles CO 2 per mole of ionic liquid.

20. A method for capturing a gaseous electrophilic species, the method comprising contacting said gaseous electrophilic species with an ionic liquid according to claim 1 .

21. The method according to claim 20 , further comprising removing captured electrophilic gas from said ionic liquid to produce fresh ionic liquid, and re-using said fresh ionic liquid for capturing additional electrophilic gas.

22. A method for capturing gaseous carbon dioxide, the method comprising contacting said carbon dioxide with an ionic liquid according to claim 1 .

23. The method according to claim 22 , wherein the carbon dioxide is nucleophilicly attacked by the deprotonated phenolic or thiophenolic anion.

24. The method according to claim 22 , wherein the carbon dioxide is not protonated during the reaction.

25. The method according to claim 22 , wherein said method for capturing gaseous carbon dioxide is integrated with a process that produces carbon dioxide as a byproduct.

26. The method according to claim 25 , wherein said process that produces carbon dioxide as a byproduct is a combustion process.

27. A method for capturing atmospheric sulfur dioxide, the method comprising contacting said sulfur dioxide with an ionic liquid according to claim 1 .

28. The method according to claim 27 , wherein the sulfur dioxide is nucleophilicly attacked by the deprotonated phenolic or thiophenolic anion.

29. The method according to claim 27 , wherein the sulfur dioxide is not protonated during the reaction.

30. The method according to claim 27 , wherein said method for capturing atmospheric sulfur dioxide is integrated with a process that produces sulfur dioxide as a byproduct.

31. The method according to claim 30 , wherein said process that produces sulfur dioxide as a byproduct is a combustion process.

32. The method of claim 31 , wherein said combustion process is a coal-powered process.

33. An ionic liquid composition having the following chemical structural formula:

wherein R 1 , R 2 , R 3 , and R 4 are independently selected from hydrocarbon groups containing at least 1 and up to 20 carbon atoms, provided that at least one of R 1 , R 2 , R 3 , and R 4 contains at least four more carbon atoms than another of R 1 , R 2 , R 3 , and R 4 ; and X − is a deprotonated phenolic or thiophenolic anion reactive with carbon dioxide or sulfur dioxide.

34. A method for capturing a gaseous electrophilic species, the method comprising contacting said gaseous electrophilic species with an ionic liquid according to claim 33 .

35. The method of claim 34 , wherein the gaseous electrophilic species is carbon dioxide or sulfur dioxide.