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 CO2 + 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 (kH(2), CH2, kH(2), CH3, kCO(2), CH2, and kCO(2), CH3) 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 CO2 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.