Excess molar enthalpies for mixtures of supercritical carbon dioxide and water + ethanol solutions

Abstract

Excess molar enthalpies ( H m E ) for mixtures of supercritical CO 2 and ethanol aqueous solutions were measured at 323.15 K and 7.64 and 15.00 MPa using an isothermal high-pressure flow calorimeter. H m E values obtained at the lower pressure are very exothermic while those obtained at the higher pressure are moderately endothermic. H m E for CO 2 + H 2O mixtures at 308.15 K and 7.64 MPa and 323.15 K and 15.00 MPa were also measured. These data are examined together with H m E data previously reported for mixtures of supercritical CO 2 and ethanol aqueous solutions, vapor–liquid equilibrium data for the ternary system CO 2 + H 2O + ethanol and the excess enthalpy data for the three related binary systems. CO 2–ethanol interactions are shown to be the main contribution to excess enthalpies when supercritical CO 2 and ethanol aqueous solutions are mixed. Ternary excess enthalpies for CO 2 + H 2O + ethanol are also obtained. Kohler's method is used for estimating these ternary data from the excess enthalpy data of the three related binary systems.