Application of a non-cubic equation of state to predict the solid-liquid-vapor phase coexistences of pure alkanes

Abstract

A methodology to predict solid-liquid, solid-vapor, and liquid-vapor phase coexistences using a non-cubic equation of state is presented. The solid phase is additional to the liquid and vapor phases that can be worked with a cubic equation of state; thus, the triple point of the substance is represented. For a given substance, the seven parameters of this equation of state are obtained using the following data: the liquid-vapor critical point, acentric factor, boiling point temperature, and triple point temperature. The procedure to do this is described and is used to validate the methodology through obtaining the pure component parameters of this equation of state for 40 pure alkanes. As examples of the capacity of the reported non-cubic EoS to represent the coordinates of the three different phase transitions, predicted P-T and P-V phase transition diagrams are reported for methane, pentane and octane, and they are in good agreement with experimental data. This methodology is suitable to be used with any substance for which the density of solid phase is higher than that of liquid phase.