Study on the selective separation of methanol and methyl ethyl ketone from the azeotropic system using ionic liquids and their separation mechanism

•The separation of methanol - methyl ethyl ketone azeotropic system using two bis(trifluoromethanesulfonyl)imide-ionic liquids with different cations as extractants was reported.•The vapor–liquid equilibrium (VLE) data of the methanol + methyl ethyl ketone + [DMIM][NTf2] or [N4441][NTf2] systems were measured under 101.3 kPa.•The NRTL model and UNIFAC-Lei model were used to correlate the VLE data.•The separation mechanism of ionic liquids was systematically explored by quantum chemical calculation.