Solubility of CO2 in 1-(2-hydroxyethyl)-3-methylimidazolium ionic liquids with different anions

The solubility of carbon dioxide in a series of 1-(2-hydroxyethyl)-3-methylimidazolium ([hemim]+) based ionic liquids (ILs) with different anions, viz. hexafluorophosphate ([PF6]−), trifluoromethanesulfonate ([OTf]−), and bis-(trifluoromethyl)sulfonylimide ([Tf2N]−) at temperatures ranging from 303.15 K to 353.15 K and pressures up to 1.3 MPa were determined. The solubility data were correlated using the Krichevsky–Kasarnovsky equation and Henry’s law constants were obtained at different temperatures. Using the solubility data, the partial molar thermodynamic functions of solution such as Gibbs free energy, enthalpy, and entropy were calculated. Comparison showed that the solubility of CO2 in the ILs studied follows the same behaviour as the corresponding conventional 1-ethyl-3-methylimidazolium ([emim]+) based ILs with the same anions, i.e. [hemim][NTf2] > [hemim][OTf] > [hemim][PF6] > [hemim][BF4].