Isobaric vapor liquid equilibrium (VLE) for the acetonitrile-n-propanol system containing different ionic liquids (ILs) at atmospheric pressure (101.3 kPa) was measured. The employed ionic liquids (ILs) are 1-benzyl-3-methylimidazolium chloride ([BzMIM][Cl])

1-benzyl-3-methylimidazolium bromide ([BzMIM][Br]) and 1-hexyl-3-methylimidazolium bromide ([HMIM][Br]). The results showed that all the three ILs could enhance the relative volatility of acetonitrile to n-propanol. The order of the separation ability of ILs is [BzMIM][Cl] > [BzMIM][Br] > [HMIM][Br]. The ternary vapor liquid equilibrium experimental data were fitted with the nonrandom two-liquid (NRTL) model. It was demonstrated that NRTL model was suitable for the description of the ternary system of acetonitrile + n-propanol + IL.