Liquid−Liquid Equilibria for Binary and Ternary Polymer Solutions with PC-SAFT

Two algorithms for evaluating liquid−liquid equilibria (LLE) for binary and ternary polymer solutions are presented. The binary algorithm provides the temperature versus concentration cloud-point curve at fixed pressure, whereas the ternary algorithm provides component 1 versus component 2 concentration coexistence curves at fixed pressure and temperature. The algorithms automatically trace the entire liquid−liquid coexistence curves in steps by adjusting the step size, generating initial estimates, and subsequently solving the phase-equilibrium problem by a second-order method. The algorithms are used for investigating the correlative and predictive capabilities of the thermodynamic model PC-SAFT. The investigation shows that the model correlates well experimental LLE data for binary as well as ternary systems but further predicts the behavior of the ternary systems with reasonably good accuracy, even by using interaction parameters obtained from binary vapor−liquid equlibrium data.