Binary interaction parameters for nonpolar systems with cubic equations of state: a theoretical approach 1. CO2/hydrocarbons using SRK equation of state

This work shows that, when suitable theoretically based combining rules are used for the cross energy and cross co-volume parameters, cubic equations of state (EoS) with the van der Waals one-fluid mixing rules can adequately represent phase equilibria for the asymmetric CO2/hydrocarbon mixtures. These combining rules lead to semi-theoretical yet simple, meaningful and successful correlations for the interactions parameters Kij (of the cross-energy term) and lij (of the cross volumef term). Unlike previous correlations, the proposed equations relate the interaction parameters only to the pure component co-volume (bi) parameters, meaning that no additional critical volume), besides those required by the EoS itself (the critical temperature Tc, the critical pressure Pc and the acentric factor) are used. Furthermore, the form of the correlations enables us to tune easily the cubic EoS when this is required for the prediction of phase behavior of petroleum fluids. A brief theoretical analysis on the temperature dependency of the Kij interaction parameter is also presented.