Excess enthalpies of (carbon dioxide + propylene carbonate or N-methyl-ε-caprolactam or 1-formyl piperidine) at the temperatures 298.15 K and 308.15 K and pressures from 7.5 MPa to 12.5 MPa

Abstract

The excess molar enthalpies H E mof [ xCO 2+ (1 − x){C 4H 6O 3(propylene carbonate) or C 7H 13NO ( N-methyl-ε-caprolactam) or C 6H 11NO (1-formyl piperidine)}] were measured at the temperatures 298.15 K and 308.15 K and pressures (7.5, 10.0, and 12.5) MPa. (Vapour + liquid) phase boundaries were determined from the H E ms. The excess enthalpies for all of the mixtures are negative over the entire composition, temperature, and pressure range. Large changes in the values of H E mwere observed near the critical temperature and pressure of carbon dioxide. The Peng-Robinson equation of state with a composition-dependent interaction parameter was used to model the behaviour of H E m. At low xthe Peng-Robinson equation provided a satisfactory fit for all mixtures studied over the full range of pressures and temperatures. For { xCO 2+ (1 − x)C 4H 6O 3}, the predicted H E mvalues for x> 0.5 were more negative than the experimental results. The fits to the other mixing curves were somewhat better, but show similar discrepancies at T= 308.15 K and p= 7.5 MPa.