Prediction of vapor–liquid equilibrium in water–alcohol–hydrocarbon systems with the dipolar perturbed-chain SAFT equation of state

Abstract

It is well known that water–alcohol–hydrocarbon systems are very difficult to model due to the existence of hydrogen bonding interactions, permanent dipole–dipole interactions and induced dipole–permanent dipole interactions. Although the statistical association fluid theory (SAFT) which is a successful model to describe hydrogen bonding interactions has been employed for such systems before, neglecting some intermolecular interactions necessitates the introduction of an adjustable binary interaction parameter to reproduce the VLE data. This of course limits the SAFT as a predictive tool. Among these interactions which may influence the phase behavior and have not been considered in the original form of the SAFT are the dipole–dipole interactions. Recently, three approaches, namely, Jog and Chapman, Gross and Vrabec, and Economou have been proposed to incorporate such interactions in SAFT. In this study, water–alcohol–hydrocarbon systems are modeled by the inclusion of the three dipolar theories to the perturbed-chain statistical association fluid theory (PC-SAFT) where different classes of alcohols are considered including glycols. A comparison of the performance of the three approaches is presented by using data from 53 binary systems. Finally, it is demonstrated that binary data are not necessarily needed to estimate pure component parameters.