Isobaric VLE data for the system of butan-1-ol + butyl ethanoate + 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide

• Vapor–liquid equilibrium (VLE) for the azeotropic mixture with ionic liquid.
• The addition of ionic liquid enhanced the relative volatility.
• Use the NRTL activity coefficient model to correlate the experimental VLE data.
• The correlated results and the experimental data agreed well.

Vapor–liquid equilibrium (VLE) for the ternary system of butan-1-ol + butyl ethanoate + 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ([BMIM][NTf2]) and the binary system of butan-1-ol + [BMIM][NTf2], as well as butyl ethanoate + [BMIM][NTf2] were measured at 101.3 kPa. The experimental VLE data were correlated by the nonrandom two-liquid (NRTL) activity coefficient model, and the correlated results agreed well with the experimental data. The results showed that the addition of ionic liquid ([BMIM][NTf2]) to the azeotropic mixture produced a notable salting-out effect, which enhanced the relative volatility of butan-1-ol to butyl ethanoate. The ionic liquid entrainer [BMIM][NTf2] was compared with the conventional entrainer ethylene glycol, and [BMIM][NTf2] is more effective for the separation of the azeotropic mixture of butan-1-ol + butyl ethanoate via extractive distillation.