New equation of state for mixtures of nonspherical molecules based on statistical mechanics

Abstract

Equations of state are models that describe the thermodynamic behavior of chemical systems, and are used to estimate relevant thermophysical properties for the modeling and optimization of industrial processes. Among the different classes of thermodynamic models, equations of state based on Statistical Mechanics excel by incorporating concepts of thermodynamic perturbation theory (TPT), which makes possible the study of complex systems from minor perturbations in the Hamiltonian function of simpler systems. With the concepts of Statistical Mechanics, especially the TPT, statistical thermodynamic models -- such as the BACK, SAFT and SAFT-BACK equations of state -- feature a high predictive capacity, providing a better description of molecular systems, even though they still dependend on correlations to experimental data of phase equilibria. Thus, a crucial point to be considered in the development of new thermodynamic models is the choice of a reference fluid that captures the tendency of the molecular behavior of the studied system. In this project, we propose the development of a new equation of state for fluid mixtures of different nonspherical geometries. The development of this new equation will be based on Onsager's theory, on Monte Carlo molecular simulations, on methodologies present in the literature for calculating liquid-liquid and liquid-vapor equilibrium phase diagrams and on methodologies developed by us in recent works to calculate the full Helmholtz free energy via molecular simulation. Finally, to assess the predictive capacity of the model, results obtained from the new equation of state will be compared with experimental data from the open literature.