Temperature and Composition Dependence of the Thermodynamic Properties of an Aqueous Solution of 1-Ethyl-3-methylimidazolium Formate and 1-Ethyl-3-methylimidazolium Acetate

Abstract

New experimental data on the thermodynamic properties of imidazolium-based ionic liquids (ILs) and {IL + water} solutions are presented. The isothermal (vapor + liquid) phase equilibrium (VLE) and the density of binary mixtures composed of 1-ethyl-3-methylimidazolium formate, [EMIM][HCOO], or 1-ethyl-3-methylimidazolium acetate, [EMIM][CH3COO], and water are demonstrated. The experimental data were measured at temperatures from 298.15 to 348.15 K over a wide IL mole fraction under ambient pressure. Both ILs were delivered by IoLiTec, and the water content was determined by the Karl–Fischer titration technique. The thermophysical properties of the pure ILs, that is, glass-transition temperature, heat capacity at glass-transition change, and the temperature and enthalpy of melting, were determined by differential scanning calorimetry technique. The VLE has been measured by an ebulliometric method at temperatures from 338.15 to 368.15 K and pressures up to 85 kPa. The experimental VLE data were tested for thermodynamic consistency using the Van Ness test. The nonrandom two-liquid model equation was used to correlate the experimental VLE data. The density of the tested aqueous solution has been measured as a function of IL’s mole fraction over a wide temperature range. The empirical equations were applied for density data correlation. From the experimental density data for the {[EMIM][CH3COO] (1) + water (2)} system, the excess molar volumes were determined and correlated using the Redlich–Kister equation.