Fluid Phase Equilibria, Vol.485, 264-269, 2019
Updated versions of the generalized Soave alpha-function suitable for the Redlich-Kwong and Peng-Robinson equations of state
More than 40 years after their publication, updated versions of the generalized Soave alpha-function (alpha(T-r,omega) = [1 + m(omega)(1 T-r(0.5))](2)) suitable for the Redlich-Kwong (RK) and Peng-Robinson (PR) equations of state (EoS) are proposed in this work. The new mathematical expressions of m(RK)(omega) and m(PR)(omega)) have been determined by correlating the optimal m values, fitted on vapor pressures (P-sat) and/or enthalpies of vaporization (Delta H-vap) and/or saturated-liquid heat capacities (C-p,liq(sat)) against the acentric factor omega. The correlations determined in this study can be considered as broad-based and sound since they were established for 1721 pure compounds belonging to many different chemical families (hydrocarbons, halogenated, oxygenated, sulfur, nitrogen compounds ...) for which experimental data were available. Significant improvements on the reproduction of vapor pressures were obtained for the PR EoS with respect to the original version. The updated SRK EoS achieved similar average deviations for the three properties of interest (P-sat,Delta H-vap and C-p,liq(sat)), in comparison with the original SRK equation. A substantial improvement is however noticeable for heavy molecules with an acentric factor larger than 0.9. (C) 2018 Elsevier B.V. All rights reserved.