Vapor–liquid equilibrium for the ternary carbon dioxide + ethanol + n-hexane and quaternary carbon dioxide + ethanol + n-hexane + thiophene systems

In this work, the experimental vapor–liquid equilibria (VLE) for a ternary and a quaternary system was measured in a static–analytic apparatus from subcritical up to near critical pressures of the systems. The VLE for the ternary carbon dioxide + ethanol + n-hexane system was determined at (313.66, 342.82 and 372.76) K. VLE for the same components in the presence of thiophene was obtained at (313.11, 343.39 and 373.06) K. Combined uncertainties for the measured properties were estimated to be ±0.008 MPa, ±0.03 K, ±0.0019 mol/mol for the vapor phase and ±0.0038 mol/mol for the liquid phase with respect to carbon dioxide composition. A high selectivity of n-hexane over ethanol and thiophene was obtained in both systems in the presence of carbon dioxide for the studied range of temperature and pressure. The vapor–liquid equilibrium data were correlated with the Peng–Robinson equation of state using the classical mixing rule.

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► VLE data of carbon dioxide + ethanol + n-hexane, and +thiophene from (313 to 363) K.
► A static-analytic apparatus with a ROLSI sampler was used.
► Equilibrium ratios Ki and relative volatilities αij were evaluated for these systems.
► α32 {n-hexane (3) over ethanol (2)} were higher in the quaternary system.
► n-Hexane had higher relative volatilities than ethanol and thiophene.