| This paper study the effect of the various ILs on vapor-liquid equilibria of the water-ethanol system, select IL [bmim][OAc] which has strong interaction with water and ethanol but weak with ethyl acetate as extractant to separate water-ethanol-ethyl acetate system, the VLE data was measured and correlated by NRTL equation. At the same time, made the process simulation of the extractive distillation with [bmim][OAc] as extractant to purify ethyl acetate.T, x, y data were measured for ternary systems containing water -ethanol -IL at 100 kPa, While the mole fraction of ethanol calculated on the IL-free basis, x2' = 0.95, activity coefficients of the volatile components as well as the relative volatility were obtained from the experimental data. Eight ILs were investigated, cation including [emim]+, [bmim]+; anion including [BF4]-, [N(CN)2]-, [OAc]-, [Cl]-. Results showed that the activity coefficients are mainly decided by the anions; the interactions of the anions with water and ethanol are in the order of [Cl]-≈[OAc]- > [N(CN)2]-> [BF4]-. The similar order cancels the effect of ILs in some extent. The interactions of the cations with water and ethanol are in the reversed: for water, [emim]+ > [bmim]+; for ethanol, [emim]+ < [bmim]+; this is in favor of enhancing the relative volatility of the volatile components. Among the systems investigated, the ILs with [OAc]-or [Cl]- as the anion, and [emim]+ as the cation, have the best separation effect. The VLE data were correlated by the NRTL model. Isobaric T, x, y data were measured for quaternary system water + ethanol + ethyl acetate +1-butyl-3-methylimidazolium acetate at 100 kPa. From the experimental data, relative volatility and activity coefficients of the volatile components were obtained, NRTL parameters was correlated. Results showed the ionic liquid [bmim][OAc] can decrease the activity coefficients of water and ethanol,while increase the ethyl acetate dramaticly, therefore increaseα32 andα31 obviously. In this paper, a simulating computation of an process, separation of ternary azeotrope by extractive distillation with [bmim][OAc] as extractant, the NRTL equation as thermodynamics method, is performed using Aspen plus. The extractive distillation column is 10 theory stages, the azeotropic mixtures and the extractant feed stage are respectively 5 and 2; the ratio of solvent to feed is 0.75, the reflux ratio 0.8 and the distillate ratio 0.832 kg/kg. The mass fraction of ethyl acetate at the top and bottom is respectively higher than 99% and lower than 0.5%, [bmim][OAc] can be recovered by flash and stripping method.
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