Prediction of Activity Coefficients at Infinite Dilution by Using the Weighted Volatility Function

Abstract

Abstract A new method for calculating activity coefficients at infinite dilution is proposed, based on extrapolation of the weighted volatility functio ω=x1 In (y1/x1)+ x2 In (y2/x2), to dilute compositions. The values of ω are calculated from vapor-liquid equilibria data smoothed by an appropriate G e function. The ω function exhibits very good numerical sensitivity that improves the extrapolation capabilities of an activity coefficient model, when its parameters are adjusted to experimental VLE data instead of a bubble-point pressure fit technique. The results of the proposed method are compared with the results predicted by DECHMA and by MOSCED for 95 systems of known thermodynamic consistency and shown to be more accurate than those of DECHEMA and of equal or better accuracy to those of MOSCED. A mean deviation of 14% is achieved with respect to experiemental data on activity coefficients at infinite dilution.