Thermodynamic Study of the N2O + CO2 and N2O + CO2 + Cyclohexane Systems in the Near-Critical and Supercritical Regions

Abstract

Carbon dioxide, CO2, and nitrous oxide, N2O, are fluids used in supercritical extraction. Mixtures of N2O and CO2 are excellent candidates to be used as supercritical fluids. In this work, excess enthalpies, , are reported for the N2O + CO2 and N2O + CO2 + cyclohexane systems at 308.15 K and 7.64 MPa. This temperature lies between the N2O and CO2 critical temperatures, and the pressure is higher than the N2O and CO2 critical pressures. Measurements have been carried out using an isothermal high-pressure flow calorimeter. Results for the N2O + CO2 system are analyzed simultaneously with excess enthalpy data and excess volume data, , taken from the literature, using different equations of state and mixing rules. The magnitude of the heat involved is large because of the proximity of experimental conditions to the mixture's critical locus. Experimental data for the ternary system are analyzed using different equations of state and mixing rules, and several empirical and semiempirical prediction methods are t...