A SIMPLIFIED SAFT EQUATION OF STATE FOR ASSOCIATING COMPOUNDS AND MIXTURES

A simplified statistical associating fluid theory (SAFT) equation of state is developed for associating and nonassociating compounds. The new equation of state has the same number of adjustable parameters as the original SAFT equation, but is simpler. For pure compounds, this equation of state can correlate the vapor pressure and liquid density with errors equal to those of the original SAFT equation. Both self-associating and cross-associating binary mixtures were used to test the simplified SAFT equation of state. With a single binary adjustable parameter, the new equation results in better correlations of vapor-liquid equilibria than the original SAFT equation for most mixtures. However, for some mixtures, both the original and simplified SAFT equations of state fail to provide a satisfactory description. The optimized binary parameter of the simplified SAFT equation of state is found to be linearly dependent on temperature for each mixture. Consequently, the binary parameter computed from several data sets can be used to accurately predict the vapor-liquid equilibrium at temperatures other than those for which experimental data are available.