Improving the Separation of n-Heptane + Ethanol Azeotropic Mixtures Combining Ionic Liquid 1-Ethyl-3-methylimidazolium Acetate with Different Inorganic Salts

Abstract

In this work, the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate, [C2MIM][Ac], was combined with the inorganic salts (ISs) ammonium acetate, [NH4][Ac], ammonium chloride, [NH4]Cl, and ammonium thiocyanate, [NH4][SCN], and used as an extraction solvent for the separation of the azeotropic mixture of n-heptane + ethanol. The liquid–liquid equilibria (LLE) of the ternary mixtures of n-heptane + ethanol + IL or IL-IS was experimentally measured at 298.15 K and 0.1 MPa. The feasibility of the extraction solvents was assessed by the distribution coefficient and the selectivity. The results showed that the extraction solvents studied can be suitable candidates for the separation of ethanol from n-heptane. Additionally, we show that the solubilization of ISs in the IL can greatly increase the selectivity of the latter, while no significant impact on the distribution coefficient is verified. Moreover, the distribution coefficient values obtained for the [C2MIM][Ac] and its mixtures with ISs are the highest among neat ILs tested so far for the azeotropic mixture in study. The experimental liquid–liquid equilibrium data were correlated using the nonrandom two-liquid (NRTL) excess Gibbs free energy model.