Solubility of Phosphonium Ionic Liquid in Alcohols, Benzene, and Alkylbenzenes

The (solid + liquid) phase equilibria and (liquid + liquid) phase equilibria of binary mixtures containing quaternary phosphonium salt−tetrabutylphosphonium methanesulfonate and alcohols or alkylbenzenes were investigated. The systems {[(CH₃CH₂CH₂CH₂)₄P][CH₃SO₃] + 1-butanol, or 1-hexanol, 1-octanol, 1-decanol, or 1-dodecanol} and {[(CH₃CH₂CH₂CH₂)₄P][CH₃SO₃] + benzene, or toluene, ethylbenzene, or propylbenzene} have been measured by a dynamic method at a wide range of temperatures from 220 to 386 K. Solid−liquid equilibria with immiscibility in the liquid phase were detected with the aromatic hydrocarbons ethylbenzene and propylbenzene. The basic thermodynamic properties of pure ionic liquidthe melting point, enthalpy of fusion, enthalpy of solid−solid-phase transition, and glass transitionhave been determined by differential scanning calorimetry. The experimental data of systems with alcohols were correlated by means of the UNIQUAC ASM and NRTL1 equations and of systems with alkylbenzenes with Wilson and NRTL equations utilizing parameters derived from the (solid + liquid) equilibrium. The root-mean-square deviations of the solubility temperatures for all calculated data are dependent upon the particular system and the particular equation used.