Here, a group contribution statistical associating fluid theory equation of state (SAFT EOS) (GC-SAFT) proposed earlier by our group (Tamouza et al., Fluid Phase Equilib. 2004, 222-223, 67-76) is extended to some asymmetric systems, using a method for correlating the k ij binary parameters, using only pure compound parameters. The method is inspired by London's theory of dispersive interactions and correlates the k ij values to the "pseudo-ionization energies" of compounds i and j (denoted as J i and J j , respectively). A group contribution for the latter parameters is also proposed, in view of obtaining a more-predictive model. Correlation tests of phase equilibria are conducted on some CO 2 + n-alkane systems. Using the parameters thus obtained, the phase envelopes of other CO 2 + n-alkane systems, as well as methane + n-alkane and ethane + n-alkane systems, were fully predicted. Correlation and predictions are qualitatively and quantitatively satisfactory. The deviations are within 4%-5% (i.e., comparable to those obtained on previously investigated systems).

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 liquidÀliquid equilibrium (LLE) and vaporÀliquid equilibrium (VLE) of hydrocarbons þ 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 H 2 S is taken into account. Cross association between water and other polar molecules (CO 2 or aromatic molecules) was also taken into account explicitly. Only one set of cross association parameters ε cross /k and k cross values were used for all the water þ aromatic mixtures considered here. ε cross /k was adjusted on experimental data, whereas k 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 [

A group-contribution statistical associating fluid theory equation of state (GC-SAFT EOS) that was proposed by Tamouza et al. [Tamouza et al. Fluid Phase Equilib. 2004, 222−223, 67−76], which was extended in the first part in this series of papers to the asymmetric systems CO2 + n-alkane, methane + n-alkane, and ethane + n-alkane, is further tested here on binary mixtures that contain aromatic hydrocarbons, n-alkanes, CO2, N2, and H2S. The method for correlating the binary interaction parameters (k ij ), which is inspired by Londonʼs theory of dispersive interactions, uses only pure compound adjustable parameters (“pseudo-ionization energies” of compounds i and j, denoted as J i and J j ). A group contribution for the latter parameters also is used for n-alkane and alkyl benzene series. Numerous prediction tests on the aforementioned cited systems were performed in a systematic and comprehensive way. Predictions are both qualitatively and quantitatively satisfactory, within deviations (4%−5%) that are comparable to those obtained on previously investigated systems (n-alkane + n-alkane, n-alkane + aromatic, n-alkane + n-alkanol).