Evaluation of an Equation of State Method for Calculating the Critical Properties of Mixtures

The accuracy of an equation of state method for predicting critical properties of mixtures is evaluated and compared to several empirical methods. The Soave equation of state is used with binary interaction coefficients predicted from vapor–liquid equilibrium data. An extensive data base of about 1500 points each for critical temperature and critical pressure is used in the evaluation. These data include hydrocarbon mixtures and hydrocarbon–non–hydrocarbon mixtures with H₂, N₂, CO, CO₂, and H₂S. The equation of state method is determined to be more accurate than the empirical methods for critical temperature and critical pressure and slightly less accurate for critical volume. Furthermore, the equation of state method predicts anomalous trends in critical loci which were previously noncalculable by empirical methods.