PREDICTION OF VAPOR-PRESSURE FOR NONAQUEOUS ELECTROLYTE-SOLUTIONS USING AN ELECTROLYTE EQUATION OF STATE

The aqueous electrolyte equation of state (EOS) developed by Furst and Renon [W. Furst, H. Renon, AIChE J. 39 (1993) 335-343] has been exten ded to nonaqueous electrolyte solutions. Binary interaction parameters for ion-solvent and ion-ion pairs are estimated from ionic Stokes and Pauling diameters. The temperature dependence of the interaction para meters involving ions has been neglected since the temperature range i n question is from 278.15 to 348.25 K. The extended electrolyte EOS ha s been used to calculate vapor pressures and mean ionic activity coeff icients of nonaqueous solutions of single electrolytes without any adj ustable parameters. The predicted results are quite satisfactory, the overall average absolute deviation (AAD) for predicted vapor pressure being approximately 1%. In addition, the extended electrolyte EOS has been compared with the electrolyte NRTL model of Mock et al. [B. Mock, L.B. Evans, C.C. Chen, AIChE J. 32 (1986) 1655-1664], with the extend ed electrolyte UNIQUAC models of Sander et al. [B. Sander, Aa. Fredens lund, P. Rasmussen, Chem. Eng. Sci. 41 (1986) 1171-1183] and Macedo et al. [E.A. Macedo, V. Skovborg, P. Rasmussen, Chem. Eng. Sci. 45 (1990 ) 875-882] and also with the one and three adjustable parameter models of Fitter [K.S. Fitter, J. Phys. Chem. 77 (1973) 268-277]. The deviat ions obtained by the application of our electrolyte EOS to various non aqueous systems are of the same order of magnitude as those obtained b y the models of Mock ct al., Sander et al. and Macedo ct al. as well a s by Fitter's model with one adjustable parameter, although our model is a predictive one. (C) 1997 Elsevier Science B.V.