Modeling of solid-fluid equilibria of pure n-alkanes and binary methane + n-alkane systems through predictive correlations

Abstract

In this work, we systematically study the phase behavior of the binary systems homologous series of methane with heavier n-alkanes, by considering the appearance of fluid and pure solid phases. The Peng-Robinson (PR) and the generalized Redlich–Kwong–Peng–Robinson (RK-PR) equations of state (EoS) are coupled to a solid fugacity model which considers the solid phase as only formed by the pure heavy compound. Correlations are developed here for all the solid fugacity model parameters, as functions of the n-alkane carbon number; and a high-quality reproduction of the melting curves of pure n-alkanes is obtained. Furthermore, diagrams of the global phase behavior, as well as solid-fluid isopleths, in wide ranges of conditions are computed through numerical continuation methods. The evaluation and comparison of results show that both PR and RKPR, associated to the solid fugacity model with the correlations here developed, are able to correctly predict the solid-fluid phase behavior of the studied mixtures along the methane + n-alkane series, although the predictions obtained with the RK-PR model are more accurate, especially for the more asymmetric systems.