Measurement of activity coefficients at infinite dilution of organic solutes in the ionic liquid 1-ethyl-3-methylimidazolium 2-(2-methoxyethoxy) ethylsulfate at T = (308.15, 313.15, 323.15 and 333.15) K using gas + liquid chromatography

Abstract

In this study, the interactions between volatile organic compounds and the ionic liquid (IL) 1-ethyl-3-methylimidazolium 2-(2-methoxyethoxy) ethylsulfate [EMIM]+[MDEGSO4]− were investigated using gas+liquid chromatography measurements. The activity coefficients at infinite dilution γ13∞ were determined for 28 polar and non-polar organic solutes (alkanes, cycloalkanes, alkenes, alkynes, aromatic compounds, alcohols, and ketones) in 1-ethyl-3-methylimidazolium 2-(2-methoxyethoxy) ethylsulfate at T=(308.15, 313.15, 323.15 and 333.15)K. Packed columns with phase loadings of 0.27 and 0.37 mass fraction of the IL in the stationary phase were employed to obtain γ13∞ values at each temperature. Density and refractive index values were also measured for the pure IL at P=0.1MPa and at the experimental temperatures. Partial molar excess enthalpies at infinite dilution ΔH1E,∞ were calculated for the solutes from the temperature dependency of the γ13∞ values. The uncertainties in the activity coefficient at infinite dilution were critically evaluated and estimated on average to be ±5.3%. Selectivity values at infinite dilution Sij∞ for the hexane/benzene separation were also calculated at T=308.15K. The selectivity Sij∞ value of the IL investigated in this study is approximately 3.7 times greater than that for NMP, 2.6 times greater than that for NFM, and 2.3 times greater than that for sulfolane. These results indicate the potential use of this IL in extractive separation processes.