(189bn) Thermodynamic Properties and Molecular Interactions of Azeotropic Mixtures Using Molecular Simulation and Modeling

The occurrence of azeotropes poses great challenges for separation processes based on vapor-liquid equilibria (VLE), such as distillation, where the liquid and vapor phases have identical compositions. Despite the abundance of experimental data of many azeotropic systems, understanding into the molecular mechanism is lacking which is impeding the design of more efficient separation processes. In this study, we use the united atom transferable potentials for phase equilibria (TraPPE-UA) force-field to model, at the molecular level, different azeotropic systems with both positive and negative deviations (from the ideal solution). VLE of these mixtures are explored using Gibbs ensemble Monte Carlo (GEMC) simulation. Our VLE results agree well with experimental data. Partial thermodynamic properties of different components in the mixtures are calculated to reveal the molecular origin for the strong departure from ideal solution behaviors. Liquid structure of the mixture is characterized for the molecular details responsible for the thermodynamic changes. Finally, we attempt at the quantitative structure-activity (QSAR) modeling for the prediction of the existence of azeotropes from the molecular constituents based on data collected from both molecular simulation and experimental measurements.