VLE measurement of binary systems containing imidazolium ionic liquids and water or ethanol

Abstract

Experimental VLE data for binary systems of ethanol or water with three 1-ethyl-3-methylimidazolium ionic liquids (ILs) containing different anions were measured at normal pressure using the Siwoloboff procedure. ILs selected in this study were those that appear to be suitable for the ethanol−water mixture separation by extractive distillation. Measured vapor–liquid equilibria were described by the extended Raoult's law with components activity coefficients calculated using the NRTL equation. Detailed analysis of the VLE data is presented in form of equilibrium diagrams, variation of activity coefficients with mixture composition and thermodynamic consistency tests. Experimental t–x data were measured within a wider range of the binary mixture compositions and compared to those found in literature. Boiling point temperature measurement of binary mixtures (adapted Siwoloboff procedure) provided comparable results to those obtained applying conventional methods of VLE estimation (circulation method, ebulliometric measurement, etc.). Reliability and thermodynamic consistency of experimental data obtained using the adapted Siwoloboff procedure for high ILs’ content (high temperature) were affected by the accuracy of the temperature measurement. However, the trend of these experimental data is useful for VLE description in concentration regions where usually only coarse extrapolation is applied. Experimental data obtained for a wide binary mixture composition range (IL content of more than 70 mole%) seem to be more suitable for binary and ternary VLE description in separation equipment simulations, e.g. extractive distillation columns.