Isobaric Vapor-Liquid Equilibria for Water plus Acetic Acid + 1-Ethyl-3-methylimidazolium Diethylphosphate at 101.32 kPa

The removal and recycling of acetic acid from aqueous solutions is important for environmental protection and resource utilization. In this work, ionic liquid (IL) 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]) as an entrainer for the extractive distillation of the system water + acetic acid was investigated. Isobaric vapor-liquid equilibrium (VLE) data of the systems acetic acid + water, water + [EMIM]-[DEP], acetic acid + [EMIM][DEP], and water + acetic acid + [EMIM][DEP] have been measured at 101.32 kPa by using an improved Rose Williams equilibrium still. The addition of [EMIM][DEP] showed a remarkable entrainer performance for the separation of acetic acid from its aqueous solution. The boiling point difference of the water + acetic acid system increased from 17.88 K (0 wt % IL) to 42.41 K (about 50 wt % IL), and the relative volatility (x(1)' = 0.9) increased from 1.60 (0 wt % IL) to 5.28 (about 50 wt % IL). On the basis of the chemical theory and the Hayden-O'Connell (HOC) method, the parameters of the NRTL model for the binary systems were obtained, and the predicted values of the ternary systems of water + acetic acid + [EMIM][DEP] fitted the experimental VLE data well.