Phase equilibria in hydrogen-containing binary systems modeled with the Peng–Robinson equation of state and temperature-dependent binary interaction parameters calculated through a group-contribution method

The study of phase equilibria in hydrogen-containing mixtures is essential for petroleum and chemical engineering, electricity production, transportation and for many other energy needs. Fluid-phase diagrams are however atypical because of the size-asymmetric nature of these mixtures and the quantum behavior of hydrogen. Therefore, the development of a thermodynamic model able to accurately predict the phase behavior of such systems over wide ranges of pressure and temperature is a difficult and challenging task. In this work, the H2 group is added to the well-established PPR78 model in order to predict mutual solubility and critical loci of hydrogen-containing systems. Such a model combines the widely used Peng–Robinson equation of state (EoS) with a group-contribution method aimed at estimating the temperature-dependent binary interaction parameters [kij(T)]. In our previous papers, 15 groups were defined: CH3, CH2, CH, C, CH4 (methane), C2H6 (ethane), CHaro, Caro, Cfused aromatic rings, CH2,cyclic, CHcyclic ⇔ Ccyclic, CO2, N2, H2S, and SH. It was thus possible to estimate the kij for any mixture containing alkanes, aromatics, naphthenes, CO2, N2, H2S and mercaptans regardless of the temperature. In this study, the addition of the H2 group makes it possible to extend the PPR78 model to hydrogen-containing systems.