Vapor pressure measurement and prediction for ethanol plus methanol and ethanol plus water systems containing ionic liquids

Vapor pressure data for ternary systems ethanol + methanol + [MMIM][DMP] (1-methyl-3-methylimidazolium dimethyl phosphate), ethanol + methanol + [EMIM][DEP] (1-ethyl-3-methylimidazolium diethyl phosphate), ethanol + methanol + [BMIM][DBP] (1-butyl-3-methyl imidazolium dibutyl phosphate), and ethanol + water + [MMIM][ DMP] were measured at ionic liquid (IL) mass fraction of 50% by a quasi-static method. The vapor pressure data were correlated with the NRTL model for nonelectrolyte solution, and the average absolute relative deviations of vapor pressure for the above systems were 0.55%, 0.42%, 0.67%, and 1.68%, respectively. On the basis of the predicted isothermal vapor-liquid equilibrium data for the ethanol + methanol and ethanol + water systems at 320 K and ionic liquid mass fraction of 50 %, it is found that all ILs show salting-out effect for ethanol. The salting-out effect follows the order [EMIM][DEP] > [MMIM][DMP] > [BMIM][DBP] for the ethanol + methanol system. Moreover, the azeotropic phenomenon in the ethanol + water system can be completely removed. Furthermore, the ethanol component in the ethanol + methanol system is converted from a heavy component to a light one due to the stronger affinity between methanol and IL involved, which is helpful for the separation of methanol and water from ethanol.