Solvent extraction of aromatics from middle distillates: Equilibria prediction method by group contribution

Abstract

This work describes a method of calculating liquid-liquid aromatics extraction of a middle distillate. The group contribution models of the ASOG and UNIFAC type are investigated. Four vapour liquid equilibrium (VLE), two solid-liquid equilibrium (SLE), three binary and six ternary liquid-liquid equilibrium (LLE) have been measured. The parameters of the models are based mainly on the data of the systems having 10–20 carbon number. VLE, SLE, and infinite dilution activity coefficient data (17–245°C) have been used for calculating interaction parameters between hydrocarbon groups and LLE data (20–80°C) for interaction parameters of dimethylformamide-hydrocarbon groups. Middle distillate representation is based on mass spectrometric and gas chromatographic analysis and on limited data of middle distillate-DMF liquid-liquid equilibrium. It is shown that the performance of ASOG and UNIFAC models are sufficiently valid in representation of data base and in extraction calculations. Considering the predictive character and the rapidi of its application this method can be useful in the preliminary study of extraction processes.