Phase equilibrium calculations at low and high pressures with a modified COSMO-SAC model

This work presents the development of a modified variant of the COSMO-SAC model, aiming to achieve reliable phase equilibrium predictions at both low and high pressures. Two major modifications of the previously published COSMO-SAC models are introduced. First, an improved combinatorial term is used to improve the results in nearly athermal and asymmetric mixtures. Second, a further separation of the hydrogen-bonding sigma profile has been introduced, differentiating the hydroxyl group belonging to water from hydroxyl groups belonging to other compounds, to improve the results in aqueous systems. The model's performance is studied for vapor-liquid equilibrium at low pressures and infinite dilution activity coefficient predictions, and it is benchmarked with respect to COSMO-SAC and COSMO-SAC 2010 models. Furthermore, the model is combined with the Peng Robinson equation of state via the Universal Mixing Rules (UMR) and applied for high pressure vapor-liquid equilibrium predictions. The results indicate that the modified COSMO-SAC model represents a reliable tool for phase-equilibria predictions for systems of various degrees of non-ideality and asymmetry.