Separation of Azeotropes Hexane + Ethanol/1-Propanol by Ionic Liquid Extraction: Liquid–Liquid Phase Equilibrium Measurements and Thermodynamic Modeling

To separate the azeotropes of hexane + ethanol/1-propanol, two ionic liquids [HMIM][BF4] and [HMIM][OTf] were adopted as extractive agents. The corresponding ternary liquid–liquid equilibrium data for the mixtures of hexane + ethanol + [HMIM][BF4], hexane +1-propanol + [HMIM][BF4], and hexane +1-propanol + [HMIM][OTf] were measured at 298.15 K and 101.3 kPa. The distribution coefficient (B) and selectivity (S) were obtained to evaluate the separation performance of the selected extractants to extract ethanol/1-propanol from the azeotropes. Meanwhile, the influence of the ILs' anions and the alcohol carbon chain length were investigated. In addition, the nonrandom two-liquid (NRTL) and universal quasichemical activity coefficient (UNIQUAC) models were adopted to correlate the ternary liquid–liquid equilibrium data, and the binary interactive parameters were regressed. Also, the calculated results of the models agreeed with the measured data. Meanwhile, the binodal curves of the ternary systems were predicted using the universial functional activity coefficient (UNIFAC) model.