Prediction of Ionic Liquid Properties. I. Volumetric Properties as a Function of Temperature at 0.1 MPa

Abstract

The prediction of molar volumes and densities of several ionic liquids has been achieved using a group contribution model as a function of temperature between (273 and 423) K at atmospheric pressure. It was observed that the calculation of molar volumes or densities could be performed using the "ideal" behavior of the molar volumes of mixtures of ionic liquids. This model is based on the observations of Canongia Lopes et al. (J. Phys. Chem. B 2005, 109, 3519-3525) which showed that this ideal behavior is independent of the temperature and allows the molar volume of a given ionic liquid to be calculated by the sum of the effective molar volume of the component ions. Using this assumption, the effective molar volumes of ions constituting more than 220 different ionic liquids were calculated as a function of the temperature at 0.1 MPa using more than 2150 data points. These calculated results were used to build up a group contribution model for the calculation of ionic liquid molar volumes and densities with an estimated repeatability and uncertainty of 0.36 % and 0.48 %, respectively. The impact of impurities (water and halide content) in ionic liquids as well as the method of determination were also analyzed and quantified to estimate the overall uncertainty.

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“…Average absolute deviations of 0.7 % and 4.4 % between the experimental molar volumes and the predicted values were obtained, respectively. The first value is coherent with the uncertainty of 0.5 % claimed by Jacquemin et al [25] The value of 4.4 %, higher but acceptable, can be due to the contribution of the anion [C 8 SO 4 ] À , calculated by Jacquemin et al using only few experimental data. [25] Gas solubility…”

“…Their densities were similar to the density of 1-hexyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)imide [C 6 mIm][Tf 2 N] (1.37 g cm À3 at 303 K). [25] The logarithm of the densities was fitted as a linear function of temperature:…”

“…[25][26][27] Using this tool, we have calculated the densities of the functionalized ionic liquids studied in the present work. Canongia Lopes et al [28] have observed that the molar volume of an ionic liquid can be calculated as the sum of the effective molar volumes of the component ions at a given temperature.…”

“…Canongia Lopes et al [28] have observed that the molar volume of an ionic liquid can be calculated as the sum of the effective molar volumes of the component ions at a given temperature. Based on this assumption, Jacquemin et al have developed a group contribution method for the calculation of ionic liquid densities as a function of temperature at 0.1 MPa [25] or at higher pressures. [29] In this model, the effective molar volume of an nalkylmethylimidazolium cation, V C n mIm ½ þ , is calculated as the sum of the molar volumes of the methylimidazolium cation [C 0 mIm] + and of the n ÀCH 2 À groups present in the alkyl chain:…”

“…According to Jacquemin et al, [25] the molar volume of each group (V group ) can be expressed as a function of temperature:…”