A NEW EQUATION OF STATE MIXING RULE FOR THE PREDICTION OF PHASE-EQUILIBRIA FROM AVAILABLE ACTIVITY-COEFFICIENT MODEL PARAMETERS

A recently proposed mixing rule for cubic equations of state, which re duces to the van der Waals mixing rule and satisfies the second virial coefficient constraint, has been combined with activity coefficient m odel parameters recently reported in the DECHEMA Chemistry Data Series at a low isothermal temperature to predict high pressure phase behavi or for nonideal systems. Wong and Sandler (WS, 1992) and Dahl and Mich elsen (MHV 2, 1990) are two recent equation of state mixing rules that can make use of the reported activity coefficient model parameters in the equation of state mixing rule model. Although they are excellent mixing rules for correlating data for highly nonideal systems, they ha ve some shortcomings when applied to simple and asymmetric systems (Co utsikos et al., 1995; Voros and Tassios, 1993). Huang and Sandler (199 3) reported that the WS mixing rule has a significant advantage in acc uracy over the MHV 2 mixing rule. For this reason, the Wong-Sandler mi xing rule has therefore been selected in this work for comparison of t he performance of our mixing rule for its the ability to reproduce the excess free energy function of the incorporated activity coefficient model and in the prediction of the high pressure phase behavior for st rongly nonideal systems using published activity coefficient parameter s at low temperature.