In order to avoid the disadvantages of common organic solvent in extractive distillation, such as low selectivity, high volatility and poor molecular design capability, ionic liquids (ILs) were selected as en trainers for the separation of 2-butanone + ethanol azeotropic mixture. The isobaric vapor-liquid equilibrium (VLE) data were measured for the ternary systems of 2-butanone + ethanol + ILs (1-ethyl-3-methylimidazolium diethylphosohate [EMIM][DEP], 1-butyl-3-methylimidazolium diethylphosphate [BMIIVI][DEP] or 1-butyl-3-methylimidazolium dibutylphosphate [BMIM][DBP]) at 101.3 kPa. A remarkable salting-out effect was produced by the addition of IL. After the content of ILs was increased to a specific value, the azeotropic phenomenon of 2-butanone-ethanol system could be completely eliminated. The separation ability of the three ILs follows this order: [EMIM]IDEP] > [BMIM] [DEP] > [BMIM][DBP]. The VLE data are well correlated with the nonrandom two-liquid (NRTL) model. (C) 2017 Published by Elsevier B.V.