Phase equilibria of binary mixtures (ionic liquid + aromatic hydrocarbon): Effect of the structure of the components on the solubility

In this work, mutual solubilities of 24 binary mixtures containing ionic liquids (1-ethyl-3-methylpyridinium ethylsulfate, 1-ethyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide, 1-hexyl-3-methylimidazolium dicyanamide and 1-propyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide) with aromatic hydrocarbons (benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene) were determined in the range T = (293.15–333.15) K and at atmospheric pressure, and the corresponding temperature-composition phase diagrams were obtained from the density of the equilibrium phases. From the experimental data, the effect of the structure of the ionic liquid and the aromatic hydrocarbon on the solubility was analyzed and discussed. The ionic liquids reported in this work show a negligible solubility in the studied aromatic hydrocarbons and the solubility of the aromatic compounds in the ionic liquids decreases in the order benzene > toluene > ethylbenzene > xylene isomers. The experimental results show that solubility is also affected by the ionic liquid structure while the temperature has a very little effect on the phase equilibria. Finally, experimental liquid–liquid equilibrium data were satisfactorily correlated using the Non-Random Two-Liquid (NRTL) model.