The Perturbed Chain-Statistical Associating Fluid Theory (PC-SAFT) is extended to polar molecular fluids, namely dipolar and quadrupolar fluids. The extension is based on the perturbation theory for polar fluids by Stell and co-workers. Appropriate expressions are proposed for dipole – dipole, quadrupole – quadrupole and dipole – quadrupole interactions. Furthermore, induced dipole interactions are calculated explicitly in the model. The new polar PC-SAFT model is relatively complex, for this purpose a truncated polar PC-SAFT (tPC-PSAFT) model is proposed using only the leading term in the polynomial expansion for polar interactions. The new model is used for the calculation of thermodynamic properties of various dipolar and quadrupolar pure fluids. Furthermore, tPC-PSAFT is generalized to multicomponent mixtures and evaluated for a wide range of highly non-ideal polar mixtures. Binary and ternary mixtures of dipolar, quadrupolar and / or associating fluids are examined. Vapor-liquid and liquid-liquid equilibria at low and high pressures are calculated. Comparisons against PC-SAFT calculations are made. It is shown that tPC-PSAFT is an accurate model for polar fluid mixture phase equilibria. In all cases, the agreement between experimental data and model predictions is very good.

References

E.K. Karakatsani, T. Spyriouni and I.G. Economou, "Extended SAFT Equations of State for Dipolar Fluids", AIChE J., 51(8), 2328 – 2342 (2005).

E.K. Karakatsani and I.G. Economou, "Perturbed Chain-Statistical Associating Fluid Theory Extended to Dipolar and Quadrupolar Molecular Fluids", J. Phys. Chem. B, 110(18), 9252 – 9261 (2006).

E.K. Karakatsani, G.M. Kontogeorgis and I.G. Economou, "Evaluation of the Truncated Perturbed Chain – Polar Statistical Associating Fluid Theory for Complex Mixture Fluid Phase Equilibria”, Ind. Eng. Chem. Res., 45(17), 6063 – 6074 (2006).