Modeling Phase Equilibrium of H2 + n-Alkane and CO2 + n-Alkane Binary Mixtures Using a Group Contribution Statistical Association Fluid Theory Equation of State (GC−SAFT−EOS) with a kij Group Contribution Method

A group contribution (GC) method combined with a SAFT equation of state (EOS) [Tamouza et al., Fluid Phase Equilib. 2004, 222 − 223, 67 and 2005, 228 − 229, 409] is extended here to model vapor−liquid phase equilibria of binary mixtures of H 2 + n -alkanes and CO 2 + n -alkanes. Modeling these systems requires binary interaction parameters k ij that are estimated here in the same spirit as pure compound GC−SAFT parameters, i.e., through a specific group contribution method. Molecule−group interaction parameters ( k H 2,CH 2, k H 2,CH 3, k CO 2,CH 2, and k CO 2,CH 3 ) are used rather than molecule−molecule interaction parameters. Two versions of SAFT are tested here: the Perturbed-Chain SAFT (PC−SAFT) [Gross and Sadowski, Ind. Eng. Chem. Res. 2000, 40, 1244] and Variable-Range SAFT (VR−SAFT) [Gil-Villegas et al., J. Chem. Phys. 1997, 106, 4168]. The results are very encouraging, particularly for predicting binary mixtures of CO 2 and heavy n -alkanes. Mixtures that contain H 2 are modeled here with deviations that compare well with those of the classically used Grayson−Streed model.