Process for purifying an ionic liquid
The invention relates to a process for purifying an ionic liquid comprising dialkylimidazolium ions by means of stripping, wherein water vapor is used at a particular temperature. The process according to the invention is characterized in that the decomposition of the ionic liquid is minimized during the procedure of the process.
1. A process for purifying an ionic liquid of the structure Q + A − , wherein Q + is a 1,3-dialkylimidazolium ion, and wherein A − is selected from the group consisting of: dialkyl phosphate; alkyl sulphate; alkyl sulphonate; alkyl carboxylate; chloride; hydrogen sulphate; dihydrogen phosphate; monoalkyl hydrogen phosphate; and nitrate;
wherein the ionic liquid of the structure Q + A − is subjected to a stripping with water vapour having a temperature of ≤99° C.
2. The process of claim 1 , wherein, in the ionic liquid of the structure Q + A − , Q + is a 1,3-dialkylimidazolium ion, in which the alkyl groups are each independently C 1 -C 10 -alkyl groups, and A − is selected from the group consisting of: dialkyl phosphate, in which the alkyl groups are each independently C 1 -C 10 -alkyl groups; alkyl sulphate, in which the alkyl group is a C 1 -C 10 -alkyl group; alkyl sulphonate, in which the alkyl group is a C 1 -C 10 -alkyl group; alkyl carboxylate, in which the alkyl group is a C 1 -C 10 -alkyl group; chloride; hydrogen sulphate; dihydrogen phosphate; monoalkyl hydrogen phosphate, in which the alkyl group is a C 1 -C 10 -alkyl group; and nitrate.
3. The process of claim 2 , wherein, in the ionic liquid of the structure Q + A − , Q + is a 1,3-dialkylimidazolium ion, in which the alkyl groups are each independently C 1 -C 10 -alkyl groups, and A − is selected from the group consisting of: dialkyl phosphate, in which the alkyl groups are each independently C 1 -C 10 -alkyl groups; alkyl sulphate, in which the alkyl group is a C 1 -C 10 -alkyl group; alkyl sulphonate, in which the alkyl group is a C 1 -C 10 -alkyl group; alkyl carboxylate, in which the alkyl group is a C 1 -C 10 -alkyl group; dihydrogen phosphate; and monoalkyl hydrogen phosphate, in which the alkyl group is a C 1 -C 10 -alkyl group.
4. The process of claim 3 , wherein, in the ionic liquid of the structure Q + A − , Q + is a 1,3-dialkylimidazolium ion, in which the alkyl groups are each independently C 1 -C 10 -alkyl groups, and A − is dialkyl phosphate, in which the alkyl groups are each independently C 1 -C 10 -alkyl groups.
5. The process of claim 4 , wherein Q + is a 1,3-dimethylimidazolium cation or a 1-ethyl-3-methylimidazolium cation.
6. The process of claim 5 , wherein Q + is a 1-ethyl-3-methylimidazolium cation.
7. The process of claim 5 , wherein A − is diethyl phosphate.
8. The process of claim 7 , wherein Q + is a 1-ethyl-3-methylimidazolium cation.
9. The process of claim 1 , wherein the water vapour has a temperature in the range of 10° C. to 90° C.
10. The process of claim 1 , wherein the structure Q + A − has a temperature which is higher than the temperature of the water vapour used.
11. The process of claim 1 , wherein the ionic liquid is passed at least partially over a bed of filling materials or over a structured packing.
12. The process of claim 9 , wherein the structure Q + A − has a temperature which is higher than the temperature of the water vapour used.
13. The process of claim 12 , wherein the ionic liquid is passed at least partially over a bed of filling materials or over a structured packing.
14. The process of claim 13 , wherein, in the ionic liquid of the structure Q + A − , Q + is a 1,3-dialkylimidazolium ion, in which the alkyl groups are each independently C 1 -C 10 -alkyl groups, and A − is selected from the group consisting of: dialkyl phosphate, in which the alkyl groups are each independently C 1 -C 10 -alkyl groups; alkyl sulphate, in which the alkyl group is a C 1 -C 10 -alkyl group; alkyl sulphonate, in which the alkyl group is a C 1 -C 10 -alkyl group; alkyl carboxylate, in which the alkyl group is a C 1 -C 10 -alkyl group; chloride; hydrogen sulphate; dihydrogen phosphate; monoalkyl hydrogen phosphate, in which the alkyl group is a C 1 -C 10 -alkyl group; and nitrate.
15. The process of claim 14 , wherein, in the ionic liquid of the structure Q + A − , Q + is a 1,3-dialkylimidazolium ion, in which the alkyl groups are each independently C 1 -C 10 -alkyl groups, and A − is selected from the group consisting of: dialkyl phosphate, in which the alkyl groups are each independently C 1 -C 10 -alkyl groups; alkyl sulphate, in which the alkyl group is a C 1 -C 10 -alkyl group; alkyl sulphonate, in which the alkyl group is a C 1 -C 10 -alkyl group; alkyl carboxylate, in which the alkyl group is a C 1 -C 10 -alkyl group; dihydrogen phosphate; and monoalkyl hydrogen phosphate, in which the alkyl group is a C 1 -C 10 -alkyl group.
16. The process of claim 15 , wherein, in the ionic liquid of the structure Q + A − , Q + is a 1,3-dialkylimidazolium ion, in which the alkyl groups are each independently C 1 -C 10 -alkyl groups, and A − is dialkyl phosphate, in which the alkyl groups are each independently C 1 -C 10 -alkyl groups.
17. The process of claim 16 , wherein Q + is a 1,3-dimethylimidazolium cation or a 1-ethyl-3-methylimidazolium cation.
18. The process of claim 17 , wherein Q + is a 1-ethyl-3-methylimidazolium cation.
19. The process of claim 17 , wherein A − is diethyl phosphate.
20. The process of claim 19 , wherein Q + is a 1-ethyl-3-methylimidazolium cation.