Group contribution method with SAFT EOS applied to vapor liquid equilibria of various hydrocarbon series

Abstract

A new group contribution method is proposed using the statistical associating fluid theory (SAFT) equation of state (EOS), in order to describe the thermodynamic properties of hydrocarbon series. The method is developed for vapor–liquid equilibrium (VLE) calculations for a large number of hydrocarbons, with the use of several group parameters. SAFT models are chosen for the physical meaning of their parameters. These can be related to the molecular structure. Two versions of the SAFT EOS are used in this work: the original SAFT equation of state, proposed by Chapman et al. [Ind. Eng. Chem. Res. 29 (1990) 1709] and SAFT variable range (SAFT-VR) equation of state, proposed by Gil-Villegas et al. [J. Chem. Phys. 106 (1997) 4168]. The present group contribution method consists in calculating the equation of state parameters (dispersion energy ε, segment diameter σ, chain length m and square-well range parameter λ for SAFT-VR) using group contribution rules. In this paper, we have treated pure compounds of five hydrocarbon families: n-alkanes, alkyl-benzenes, alkyl-cyclohexanes, α-olefins and 1-alkanols. The results obtained are compared with those of the usual approach (fitting the molecular parameters of each compound on its own properties) and seem to be nearly equivalent. The results of the present method are comparable with those of other predictive approaches.