Vapor-liquid equilibrium for the separation of the n-hexane + ethanol azeotropic mixture with biobased entrainers guaiacol and dimethyl isosorbide

Abstract

In extractive distillation for the separation of azeotropic mixtures, eco-friendly solvents have demonstrated potential as greener alternatives to conventional entrainers. However, the absence of thermodynamic data for mixtures that include green solvents presents a significant hurdle to their practical application. This work explores, for the first time, vapor-liquid equilibrium (VLE) data for the azeotropic mixture of n-hexane and ethanol in the presence of the biobased entrainers guaiacol and dimethyl isosorbide (DMI). The VLE measurements were conducted using a Fischer Labodest VLE 502 ebulliometer with varying pressures and entrainer-to-feed ratios (E/Fs). The VLE data met the criteria of the Van Ness method and thereby pass the thermodynamic consistency test. The results confirm that the relative volatility of n-hexane to ethanol is increased by the addition of guaiacol and DMI to the mixture. Moreover, the azeotrope has been successfully removed. The VLE data were well regressed using the Non-Random Two Liquid (NRTL) thermodynamic model, which provided accurate binary interaction parameters (BIPs). The thermodynamic modeling verifies the reliability of the experimental data and its relevance for effective process design, emphasizing the viability of guaiacol and DMI as biobased entrainers for more sustainable and greener extractive distillation.