Measurement and prediction of vapor pressure in binary systems containing the ionic liquid [EMIM][DCA

Abstract

The vapor-liquid equilibrium (VLE) data for water/methanol/ethanol +1-ethyl-3-methylimidazolium dicyanamide ([EMIM][DCA]) binary mixtures were measured by a saturated vapor pressure device at different temperatures. The experimental results showed that the existence of ionic liquid (IL) has a significant effect on the VLE data for all the investigated systems. The thermodynamic model (i.e., modified UNIFAC model) for quantitative prediction has been extended to estimate the VLE data for water/methanol/ethanol + [EMIM][DCA] systems, and the relative mean deviations (RMDs) are 6.02%, 3.45% and 3.05%, respectively. Besides, the binding energy, excess enthalpies and σ -profiles were derived by the COSMO-RS model and density functional theory (DFT) calculation to further understand the nature of the interactions between ordinary matter and IL at the molecular scale. It was clear that the intermolecular interaction between [EMIM][DCA] and methanol/ethanol is weaker than that between [EMIM][DCA] and water; Moreover, the hydrogen bonding interaction is the dominant intermolecular force between [EMIM][DCA] and water/methanol/ethanol. • The vapor pressures for the binary systems of water/methanol/ethanol + [EMIM][DCA] were measured. • The popular UNIFAC-Lei model was extended to predict the VLE of these systems. • The binding energy, excess enthalpies and σ -profiles were used to understand the thermodynamic behavior at the molecular scale.