A modified group-contribution PC-SAFT equation of state for prediction of phase equilibria

The group contribution (GC) method proposed by Tamouza et al. (Fluid Phase Equilibria 222–223, (2004), 67–76) has been improved to estimate parameters of the Perturbed-Chain statistical associating fluid theory (hereby called mg-SAFT). The improvement is the “exclusion” of the over-accounting of dispersion energy between intra-molecular segments through an empirical correlation parameter. We have treated three hydrocarbon families (n-alkanes, n-alkyl-cycloalkanes and n-alkyl-benzenes); several pure compound properties such as the enthalpy of vaporization, single-phase density, speed of sound, heat capacities are predicted. The results indicate that most pure compound property predictions are satisfactory, mg-SAFT appears to offer a systematic improvement as compared to the original GC-PC-SAFT approach, but no improvement in prediction of speed of sound. Vapor-liquid equilibria of some binary mixtures are purely predicted using the mg-SAFT (kij = 0). Good agreements between the model predictions and the experimental data were found. Comparison with other existing SAFT-based group contribution approach was performed in calculating vapor pressure and saturated liquid density of heavy hydrocarbon; mg-SAFT demonstrated significant improvements in accuracy. [Display omitted]