(64g) Calculating Vapor Pressure and Concentration for Binary Mixtures through Equations of State

Equations of state (EOS) relating the variables pressure, volume, and temperature are often used in chemical engineering to predict vapor-liquid equilibrium (VLE) properties. Using cubic EOS, vapor pressures of pure substances can be found as a function of temperature and substance specific parameters using an algorithm. The purpose of this research was to extend previously existing programs for predicting pure component vapor pressure to predict vapor pressures and concentrations of binary mixtures. The Soave-Redlich-Kwong (SRK) cubic equation of state was used to generate data sets in order to better understand the relationships among the variables and parameters characterizing VLE in a binary mixture. These included critical temperature ratio, critical pressure ratio, vapor pressure ratio, and acentric factors. Standard plots such as Px, xy, and relative volatility illustrated the results. Comparisons were made among predictions of Raoult's Law, the Lewis and Randall Rule, and EOS calculations with an ideal solution mixing rule, which show different values for ideal solutions. These data sets cover a range of critical temperature ratios from 0.8 to 1.2, critical pressure ratios from 0.8 to 1.2, and acentric factors from -0.4 to 1.0, and are expected to be useful in future research applying cubic EOS to mixtures.