Isobaric Vapor–Liquid Equilibrium Experiments of Butyl Acetate + Butanol with Different Ionic Liquids at 101.3 kPa

This study examines the vapor–liquid equilibrium (VLE) of the butyl acetate + butanol binary system and the corresponding ternary mixtures containing [EMIM][OAC], [EMIM][Cl], or [BMIM][OAC]. The results show that [EMIM][OAC] and [BMIM][OAC] enhance the separation driving force and effectively eliminate azeotropic behavior. Among the tested ionic liquids, [EMIM][OAC] provides the strongest enhancement. The phase equilibrium data were correlated with the NRTL model, yielding average relative deviations (ARDs) of 4.80% for the binary system and 3.48, 3.65, and 3.57% for the ternary systems. Thermodynamic consistency tests further support the reliability of both the experimental data and the fitted model. Overall, these findings highlight the potential of ionic liquids (particularly [EMIM][OAC]) to improve separation efficiency in azeotropic systems.