Thermodynamic study of the N2O+CO2 and N2O+CO2 plus cyclohexane systems inthe near-critical and supercritical regions

Carbon dioxide, CO2, and nitrous oxide, N2O, are fluids used in supercritic al extraction. Mixtures of N2O and CO2 are excellent candidates to be used as supercritical fluids. In this work, excess enthalpies, H-m(E), are repor ted 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 temperature s, and the pressure is higher than the N2O and CO2 critical pressures. Meas urements have been carried out using an isothermal high-pressure flow calor imeter. Results for the N2O + CO2 system are analyzed simultaneously with e xcess enthalpy data and excess volume data, V-m(E), taken from the literatu re, using different equations of state and mixing rules. The magnitude of t he heat involved is large because of the proximity of experimental conditio ns to the mixture's critical locus. Experimental data for the ternary syste m are analyzed using different equations of state and mixing rules, and sev eral empirical and semiempirical prediction methods are tested.