Some difficulties on the application of the UNIFAC model for the prediction of liquid-liquid equilibrium compositions

Abstract

UNIFAC group parameters for the interaction between CH2 and CF2 (c) and CH2 and CF3 were obtained using experimental liquid-liquid equilibrium data for hydrocarbon - perfluorodecaline (PFD) and hydrocarbon - perfluoromethylcyclohexane (PFMCH) systems. Some difficulties were experienced on the use of the UNIFAC method with those particular systems, namely the group parameters dependence on the length of the hydrocarbon chain. Attempts were made to correlate UNIFAC parameters with the number of carbon atoms and temperature and the results compared with those obtained with NRTL equations.