Influence of the Interaction between Hydrogen Sulfide and Ionic Liquids on Solubility:  Experimental and Theoretical Investigation

The solubility of H₂S in a series of 1-butyl-3-methylimidazolium ([bmim]⁺) based ionic liquids (ILs) with different anions, chloride, tetrafluoroborate ([BF₄]^-), hexafluorophosphate ([PF₆]^-), triflate ([TfO]^-), and bis(trifluoromethyl)sulfonylimide ([Tf₂N]^-), and in a series of [Tf₂N] ILs with different cations, i.e., N-alkyl-N‘-methylimidazolium, 2-methyl-N-methyl-N‘-alkyimidazolium, N-alkylpyridinium, N-butyl-N-methylpyrrolidinium, and N-alkyl-N,N-dimethyl-N-(2-hydroxyethyl)ammonium has been determined using medium-pressure NMR spectroscopy. The observed solubilities are significantly higher than those reported for many other gases in ILs, suggesting the occurrence of specific interactions between H₂S and the examined ILs. Quantum chemical calculations have been used to investigate at a molecular level the interaction between H₂S and the [bmim]⁺-based ILs.