Measurements of vapour pressure data were conducted using a quasi-static ebulliometer for systems containing water, methanol, ethanol, and a mixture of (water + ethanol) in the presence of an ionic liquid (IL), namely, 1-methylimidazolium chloride ([MIm]Cl), wherein the IL-content ranged from w(2) = (0.10 to 0.50). The vapour pressure data of IL-containing binary systems were correlated by the NRTL model with an overall average absolute relative deviation (AARD) of 0.0103, and the resulting binary parameters were used to predict the vapour pressures of a ternary system (water + ethanol + [MIm[Cl) with an AARD less than 0.0077. Further, the isobaric vapour liquid equilibria (VLE) for the ternary system (water + ethanol IL) with IL-content of w(3) = (0.10, 0.30, and 0.50) for [MIm]Cl and x(3) = 0.15 for [MIm]Cl, [C(4)MIm]Cl, and [C(6)MIm]Cl were predicted at 101.3 kPa, respectively. It is indicated that [MIm]Cl presents the strongest ability to enhance the relative volatility of ethanol to water in the mixture of (water + ethanol) than that of [C(4)MIm]Cl and [C(6)MIm]Cl, which is consistent with the cationic sizes and hence the ionic hydration ability. Therefore, distillation separation of the azeotrope of (water + ethanol) can be sufficiently facilitated by the addition of [MIm]Cl at a specified content. (C) 2011 Elsevier Ltd. All rights reserved.