Acetone + 1-ethyl-3-methylimidazolium acetate phase diagram: A correlation challenge

Abstract

Several physical properties and the isobaric vapour-liquid equilibria at 101.32, 50, and 30 kPa were measured for the binary system consisting of acetone and the ionic liquid 1-ethyl-3-methyl-imidazolium acetate. Liquid-liquid equilibrium data were also measured at temperatures from 298.15 up to 328.35 K and atmospheric pressure. An hourglass-shaped miscibility gap was found. The simultaneous correlation of both VLE and LLE regions at 101.32 kPa was addressed. The NRTL model, considering different options to formulate the temperature dependence of the parameters, was tested and found unable to correlate the whole set of equilibrium data. A detailed analysis of the excess Gibbs energy demonstrated the limitations of the classical equation and allowed the definition of a new model with a correction term. A unique set of parameters were used to simultaneously correlate both sets of equilibrium data with very low deviations from experimental data. Moreover, the corrected NRTL function overcomes some uncertainty problems that may occur in liquid-liquid equilibrium calculations.