Liquid-liquid equilibrium measurements and interaction explorations for separation of azeotrope n-butyl acetate and n-butanol using three ionic liquids

Abstract

To separate the azeotropic mixture n-butyl acetate and n-butanol by liquid–liquid extraction, three ionic liquids (ILs) 1-ethyl-3-methylimidazolium dihydrogen phosphate ([Emim]H2PO4), 1-butyl-3-methylimidazolium dihydrogen phosphate ([Bmim]H2PO4) and 1-hexyl-3-methylimidazolium dihydrogen phosphate ([Hmim]H2PO4) were adopted as extractants. The liquid–liquid equilibrium data for the ternary mixtures (n-butyl acetate + n-butanol + [Emim]H2PO4/[Bmim]H2PO4/[Hmim]H2PO4) was measured at 298.15 K and 101.3 kPa. The extraction capacity of the ionic liquids was evaluated by partition coefficient and selectivity. The NRTL model was applied to fit the measured data with the root mean square deviation less than 0.009. The hydrogen bond length and interaction energy between the ionic liquids and n-butyl acetate/n-butanol was calculated and the effect of the ionic liquid cations with different carbon chain length was explored.