Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

Vapor pressure data for water, 1-propanol, 2-propanol, as well as the mixtures of {water + 1-propanol} and {water + 2-propanol}, were measured by a quasi-static ebulliometric method, in the presence of an alkylsulfate-based IL, namely, 1-ethyl-3-methylimidazolium methylsulfate ([EMIM][MS]) or 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][ES]). The experimental vapor pressure data for binary systems containing IL were correlated by NRTL model with an overall relative root mean square deviation (rRMSD) of 0.0053, and the obtained binary NRTL parameters were employed to predict the vapor pressure for two ternary systems with an overall rRMSD of 0.0196. In addition, isobaric vapor liquid equilibria were predicted for the ternary systems containing [EMIM][MS], [EMIM][ES], 1,3-dimethylimidazolium methylsulfate ([MMIM][MS]), 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]), and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [EMIM][OTf], respectively, with IL mole fraction of 0.05, 0.15, and 0.25 at 101.325 kPa. It was found that the addition of IL can enhance the relative volatility of propanol to water, and the separation ability follows the order of [MMIM][MS] greater than [EMIM][MS] greater than [EMIM][ES] greater than [EMIM][BF4] greater than [EMIM][OTf], which was further explained at electronic level with quantum chemical calculation. Therefore, the azeotropic mixtures of {water + 1-propanol}, and {water + 2-propanol} might be separated effectively by the addition of the alkylsulfate-based ILs in extractive distillation.