Modeling Liquid-Liquid and Liquid-Vapor Equilibria of Binary Systems Containing Water with an Alkane, an Aromatic Hydrocarbon, an Alcohol or a Gas (Methane, Ethane, CO2 or H2S), Using Group Contribution Polar Perturbed-Chain Statistical Associating Fluid Theory

The present paper proposes to use the group contribution (GC) polar perturbed-chain-statistical associating fluid theory (GC-PPC-SAFT) equation of state (EoS), that has already been used with success on various organic mixtures, and extend it to model simultaneously the liquid liquid equilibrium (LLE) and vapor liquid equilibrium (VLE) of hydrocarbons + water systems, in wide ranges of pressure and temperature. Mixtures of water with aliphatics, aromatics, alcohols, carbon dioxide, and hydrogen sulfide have been investigated. Pure water is assumed associative (according to the 4C association scheme) and dipolar; the aromatic compounds are quadrupolar. Alcohols are autoassociative with a 3B association scheme. A cross-association between water and alcohols or H2S is taken into account. Cross association between water and other polar molecules (CO2 or aromatic molecules) was also taken into account explicitly. Only one set of cross association parameters epsilon(cross)/k and kappa(cross) values were used for all the water + aromatic mixtures considered here. epsilon(cross)/k was adjusted on experimental data, whereas kappa(cross) is set to the value found for pure water. For each system, the same binary interaction parameter k(ij) was used for simultaneous modeling LLE and VLE. This parameter was correlated to pseudo-ionization energy parameters for pure compounds through London's dispersion force theory, and reused from previous works [Nguyen-Huynh, D.; Passarello, J.P.; Tobaly, P.; de Hemptinne, J.C. Ind. Eng. Chem. Res., 2008, 47, 8847-8858]. For pure water, the average deviation on vapor pressure is 3.36% and that on volume 4.74%. The water solubility in the organic phase is very well reproduced (AAD = 7.5% for water + n-hexane), but most importantly the hydrocarbon solubility in water shows an overall AAD of 30% which is very small considering the very low solubility values. Trends are similar for all families as tabulated in the manuscript and detailed in the Supporting Information.