A ZERO-PRESSURE CUBIC EQUATION OF STATE MIXING RULE FOR PREDICTING HIGH-PRESSURE PHASE-EQUILIBRIA USING INFINITE DILUTION ACTIVITY-COEFFICIENTS AT LOW-TEMPERATURE

The infinite dilution activity coefficients (gamma(i)(infinity)) of a solute in a solvent are important data in process separation calculati ons. These values reflect the degree of non-ideal solution behavior of the solute in the solvent. This paper investigates the use of infinit e dilution activity coefficients in cubic equation of state mixing rul es for the prediction of phase behavior at high pressures. A mixing ru le recently developed by Twu and Goon has been extended from infinite pressure to zero pressure. The methodology for extending the infinite- pressure Twu-Coon mixing rule was developed so that the zero-pressure Twu-Coon mixing rule reproduces the excess Gibbs free energy, as well as liquid activity coefficients of any activity models, with extremely high accuracy without requiring any additional binary interaction par ameters. We compare the performance of this new mixing rule with the M HV1 and Wong-Sandler mixing rules for its ability to use gamma(i)(infi nity) in the prediction of high pressure phase behavior for strongly n on-ideal systems. (C) 1998 Elsevier Science B.V. All rights reserved.