Activity coefficients at infinite dilution of organic solutes in the ionic liquid PEG-5 cocomonium methylsulfate at T = (313.15, 323.15, 333.15, and 343.15) K: Experimental results and COSMO-RS predictions

Abstract

Activity coefficients at infinite dilution γ13∞ have been determined for 25 polar and non-polar organic solutes (alkanes, cycloalkanes, alk-1-enes, alk-1-ynes, aromatic compounds, alcohols, and ketones) in the ionic liquid PEG-5 cocomonium methylsulfate with gas–liquid chromatography at four different temperatures, T=(313.15, 323.15, 333.15, and 343.15)K. Packed columns with phase loadings of 0.28 and 0.34 ionic liquid mass fraction in the stationary phase were employed to obtain γ13∞ values at each temperature investigated. Speed of sound, density, and refractive index values have also been measured for the pure ionic liquid at P=0.1MPa and T=(303.15, 313.15, 323.15, 333.15, and 343.15)K. The uncertainties in the sound speeds, densities, and refractive indices are estimated to be values of 0.9m·s−1, 0.00003g·cm−3, and 0.00002, respectively. Partial molar excess enthalpies at infinite dilution ΔH1E,∞ were calculated for the solutes from the temperature dependency of the γ13∞ values for the temperature range of this study. The uncertainties in the determinations of γ13∞ and ΔH1E,∞ values are 5% and 10%, respectively. Selectivity values at infinite dilution S12∞ for hexane/benzene, cyclohexane/benzene, hexane/hex-1-ene, and hexane/ethanol separations have been calculated. These have been compared against values obtained from COSMO-RS predictions.