Density Measurement and PC-SAFT/tPC-PSAFT Modeling of the CO2 + H2O System over a Wide Temperature Range

The aim of this work is to report the (p, p, T) densities for the CO2 + H2O system from 274.15 K to 413.15 K and for pressures up to 18 MPa. The binary mixtures were initially synthesized at compositions with a CO2 mole fraction of x(1) = (0, 0.0042, 0.0084, and 0.0124). The experimental densities were measured using a magnetic suspension balance with a high-pressure measurement cell. The densities of the CO2 + H2O solutions increased linearly with increasing pressure and decreased with increasing temperature. The partial molar volumes calculated from the experimental densities had a good agreement with the model proposed by Sedlbauer et al. The perturbed chain-statistical associating fluid theory (PC-SAFT) and the truncated PC-polar SAFT (tPC-PSAFT) equations of state were used to calculate the densities of the CO2 + H2O systems in four different cases. Different models of the CO2 and the H2O components were presented in this work. In PC-SAFT, CO2 was modeled as a nonassociation molecule, and H2O was modeled as a molecule with four associating sites. For tPC-PSAFT, CO2 was considered as a nonassociation molecule with a quadrupole moment, and H2O was a molecule with four association sites and a dipole moment. In both PC-SAFT and tPC-PSAFT, correlations were established for the association parameters of pure water and the binary interaction parameter k(12), which markedly improved the accuracy of the prediction. The improved PC-SAFT, combined with the correlated association parameters of the pure water and k(12), gave the best prediction for the experimental densities in this work and in previous studies. The density differences between the pure water and the CO2 + H2O solutions were also predicted well by the improved PC-SAFT.