COMPARISON OF 2 PREDICTIVE G(E) MODELS FOR VAPOR-LIQUID-EQUILIBRIUM CALCULATIONS

Ash (S.N. Ash, P. Ray and B.V. Detta, AIChE J., 31 (1985) 821; S.N. As h, Chem. Eng. J., 48 (1992) 183) has proposed a correlation for calcul ating the binary parameters of the Wilson g(E) model by using only pur e-component parameters: solubility parameters, molar liquid volumes, r elative van der Waals volumes and surfaces, critical properties, acent ric factors and dipole moments. To evaluate the Ash correlation the va pour-liquid equilibria for 75 binary systems, activity coefficients at ininite dilution and excess enthalpies were predicted and compared wi th experimental data and with the modified UNIFAC model (J. Gmehling, J. Li and M. Schiller, Ind. Eng. Chem. Res., 32 (1993) 178). It was fo und that the correlation of Ash and coworkers is significantly inferio r to the modified UNIFAC model and cannot be recommended for phase equ ilibrium predictions for those cases where UNIFAC parameters are avail able.