Liquid-liquid equilibria of choline chloride + 1-propanol or 2-propanol + water ternary systems at different temperatures: Study of choline chloride ability for recovering of these alcohols from water mixtures

Abstract

1-propanol or 2-propanol and water form azeotropic mixtures with the minimum boiling point at constant pressure. The separation of these azeotropes is an important issue in the chemical industries. Their separation by simple distillation is basically impossible, and the extractive distillation consumes much more energy than liquid- liquid extraction. For a better understanding of extraction processes, liquid-liquid equilibrium data containing binodal data and tie-lines are essential. The aim of this work is investigating the choline ability for recovering 1-propanol and 2-propanol from water mixtures by liquid-liquid extraction method. In this respect, binodal data and tie-lines were experimentally measured for (1-propanol or 2-propanol + choline chloride + water) systems at T = (298.15, 308.15 and 318.15) K under atmospheric pressure (≈85 kPa). The phase-separation ability of these systems was discussed on the basis of the solubility of the constitutive alcohol. Moreover, the critical concentration of the choline, slope and tie-line length for these systems were determined and the obtained results were used to evaluate temperature influence on these parameters. Two empirical equations consist of the Merchuk equation and a logarithmic equation with the temperature dependency was utilized for representing the experimental binodals. Furthermore, the experimentally obtained compositions for tie-lines were correlated by Othmer-Tobias, Bancraft, Bachman, and Setschenow equations and non-random two-liquid models (e-or m-NRTL). Finally, the distribution coefficients and selectivity of the studied alcohols in this work were computed and compared with the same values reported for these alcohols in the literature using other ionic liquids. It was found that the choline has more ability for breaking of azeotropes formed between 1-propanol or 2-propanol and water.