Ionic liquid 1-ethyl-3-methylimidazolium dicyanamide ([C(2)mim][DCA]) and a mixture of ionic liquids [C(2)mim][DCA] + 1-ethyl-3-methylimidazolium acetate ([C(2)mim][OAc]) were used as extractive distillation solvents to separate tert-Butyl alcohol (TBA) + water. The vapor-liquid equilibria for TBA + water + [C(2)mim][DCA] and TBA + water + [C(2)mim][DCA] + [C2(m)im][OAc] were measured at 1013 kPa. The NRTL model was employed to correlate the vapor-liquid equilibrium data, and the binary interaction parameters were obtained. The experimental results show that both of the solvents can improve the relative volatility of TBA to water, and completely destroy the azeotropic point of TBA-water. There is no synergistic effects between [C(2)mim][DCA] and [C(2)mim][OAc], and the selectivity of [C(2)mim] [OAc] is higher than that of [C(2)mim][DCA], but the viscosity of [C(2)mim][DCA] is lower. (C) 2019 Elsevier B.V. All rights reserved.