Modeling of the volumetric properties and estimation of the solubility parameters of ionic liquid + ethanol mixtures with the Sanchez–Lacombe and Simha–Somcynsky equations of state: [EMIM]Ac + ethanol and [EMIM]Cl + ethanol mixtures

Abstract

A variable-volume view-cell equipped with a motorized pressure generator was utilized to collect PVT data for two different ionic liquids, [EMIM]Ac and [EMIM]Cl, and their mixtures with ethanol which are of interest as alternative solvents for processing of lignocellulosic materials. Continuous density data were generated from 10 to 40MPa at temperatures of 298, 323, 348, 373, and 398K. Pressure scans were performed on both ILs, ethanol, and their mixtures with 5, 25, 50, and 75wt% IL content. The density data were used to determine the parameters for the Sanchez–Lacombe (S-L) and Simha–Somcynsky (S-S) equations of state (EOS). The S-L EOS was then employed to estimate isobaric expansivity, isothermal compressibility, internal pressure, free-volume fractions, and the solubility parameters for these mixtures. The S-S EOS was also used to evaluate the free-volume fractions, and the solubility parameters as this EOS provides more direct assessments of these quantities. The manuscript provides for the first time solubility parameter values for [EMIM]Cl. The manuscript for the first time also provides solubility parameter values at pressures above ambient pressure for both of these ionic liquids, for ethanol, and for their mixtures. The solubility parameters estimated for [EMIM]Ac at 10MPa and 298K were around 22.7MPa0.5 by S-L EOS, and around 21.8MPa0.5 by S-S EOS as compared to the literature value of 23.1MPa0.5 reported at ambient pressure and at 313K.