Liquid-liquid equilibria of imidazolium ionic liquids having bistriflamide or triflate anions with aromatic non-polar and polar compounds

Abstract

Liquid-liquid equilibria (LLE) of the solutions of imidazolium ionic liquids having bistriflamide [NTf2](-) and triflate [OTf](-) anions with non-polar (benzene, toluene and p-xylene) and polar aromatic compounds (nicotine and aniline) were investigated. The respective temperature-composition phase diagrams were obtained at 0.1 MPa and in a temperature range 273.15 K-423.15 K. The diagrams posses the features already established for the systems of this type: (i) for the same anion, the mutual solubility continuously increases as the cation alkyl chain extends; (ii) the mutual solubility of the imidazolium ionic liquids having bistriflamide [NTf2](-) anion is higher compared to that when the triflate [OTf](-) anion is present; (iii) the solubility is reduced as the alkylation of the benzene ring increases. However, the LLE results for the solutions [C(n)mim][OTf] + nicotine/or aniline) demonstrate a very sudden effect of the cation chain length on the liquid phase behavior. In particular, the addition of only two CH2 groups to the chain drastically increases the mutual solubility making the respective solutions always homogeneous. The experimental liquid-liquid equilibria (LLE) data for the [C(2)mim][OTf] + aniline, [C(4)mim][OTf] + aniline, and [C(2)mim][OTf] + nicotine systems were modeled using the UNIQUAC equation. The agreement of calculated compositions with experimental data is very satisfactory.