Prediction of Critical Temperature and Critical Volume of Mixtures by a New Group Contribution Method

Abstract

The vapor–liquid critical properties of mixtures are essential for defining the vapor–liquid phase boundary and play a crucial role in predicting various thermophysical properties of mixtures, which are particularly significant in applications such as supercritical extraction and transcritical cycles. While experimental measurement is the most efficient and direct approach to obtaining critical properties, it is often time-consuming and labor-intensive, necessitating the use of theoretical prediction methods. Nonetheless, existing prediction models tend to be complex and frequently rely on the critical properties of pure substances, which limit their applicability. In this article, a new group contribution method for predicting the critical temperature and critical volume of mixtures is proposed. The new group contribution method is simple in calculation form, simple in group division, has good accuracy, and does not need the critical temperature and critical volume of pure substances when calculating the critical temperature and critical volume of mixtures. This new method includes 24 groups and can be applied to systems consisting of organic compounds made up of C, H, O, F, Cl, Br, and I elements or CO₂. The experimental critical temperatures of 272 compounds and 368 groups of binary mixtures (3223 data points), as well as the experimental critical volumes of 224 compounds and 68 groups of binary mixtures (400 data points), were used to determine the group contribution values and model parameters. The average absolute relative deviations (AARDs) for the correlation of compounds are 1.28% for critical temperature and 4.93% for critical volume. For binary mixtures, the AARDs are 1.62% for the critical temperature and 7.33% for the critical volume. Additionally, the predictive capability of the new method for critical temperature and critical volume has been evaluated. The AARDs for critical temperature are 2.48, 1.98, and 0.94% for 25 data points of pure substances, 615 data points of binary mixtures, and 565 data points of ternary mixtures, respectively. For critical volumes, the AARDs are 5.52% for 26 data points of pure substances and 7.49% for 61 data points of binary mixtures.