Calculation for liquid–liquid equilibria of quaternary alkane–ethyl acetate–methanol–water systems used in counter-current chromatography

The calculation of liquid–liquid equilibrium compositions of solvent systems is very important for the work on counter-current chromatography (CCC), especially the phase composition and volume ratio obtained from liquid–liquid equilibrium calculation. In this work, liquid–liquid equilibria of quaternary Arizona solvent systems, alkane–ethyl acetate–methanol–water, and related ternary systems are correlated and predicted using the non-random two-liquid model (NRTL). Hexane, heptane and isooctane are the used alkanes. The parameters in the model are regressed only with the special systems considered. Detailed comparison with experimental data shows that liquid–liquid equilibria of these systems can be predicted with greatly improved accuracy as compared to the group contribution method (UNIFAC).