Thermophysical Properties and Water Saturation of [PF6]-Based Ionic Liquids

Abstract

In this work, mutual solubilities of two [PF6]-based ionic liquids (ILs) with water and their thermophysical properties, namely, melting properties of pure ILs and densities and viscosities of both pure and water-saturated ILs, were determined. The selected ILs comprise 1-methyl-3-propylimidazolium and 1-methyl-3-propylpyridinium cations combined with the anion hexafluorophosphate. Mutual solubilities with water were measured in the temperature range from (288.15 to 318.15) K. From the experimental solubility data dependence on temperature, the molar thermodynamic functions of solution, such as Gibbs energy, enthalpy, and entropy of the ILs in water were further derived. In addition, a simulation study based on the COSMO-RS methodology was carried out. For both pure ILs and water-equilibrated samples, densities and viscosities were determined in the temperature interval between (303.15 and 373.15) K. The isobaric thermal expansion coefficients for pure and water-saturated ILs were calculated based on the density dependence on temperature.