Separation of azeotropic mixtures using high ionicity ionic liquids based on 1-ethyl-3-methylimidazolium thiocyanate

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Abstract
The separation of azeotropic mixtures, so that their components can be reused in productions cycles, is of particular interest in modern sustainable chemical plants. In the last decade, ionic liquids have shown to possess the ability to act as extraction solvents and have been emerging as a greener alternative to organic solvents in the separation of azeotropes. Recently, high ionicity ionic liquids (HIILs) have been developed through the addition of inorganic salts to an ionic liquid, as well as by mixing two or more ionic liquids. In this work, a high ionicity ionic liquid, prepared by mixing 0.1 of 1-ethyl-3-methylimidazolium thiocyanate ([C2MIM][SCN]) and 0.9 of [C2MIM][C2SO4] was used to separate the azeotrope ethanol + heptane. Liquid–liquid equilibria for the two ternary systems: ethanol + heptane + [C2MIM][SCN] and ethanol + heptane + HIIL was measured at 298.15 K and 0.1 MPa. Both the selectivity and the distribution coefficient were used in the assessment of the extraction solvent feasibility and a correlation of these parameters with the ionicity of the solvent was established.