Predictions of high pressure phase equilibria of CO2-containing mixtures with the NRCOSMO model

NRCOSMO, a recently proposed equation-of-state model based on the COSMO approach for the quantum-mechanical description of fluids, is tested for its capacity to predict the phase equilibrium behavior of mixtures containing carbon dioxide (CO2).The advantage of the new model is that it can be used as semi-predictive equation-of-state, just needing pure component parameters, based on the benefits of the COSMO approach. Due to its equation-of-state character, this new model overcomes the inherent limitations of the original COSMO approach for the description of the gaseous or supercritical state. The NRCOSMO model needs only pure component parameters for the prediction of thermodynamic properties of multicomponent complex systems (including systems of ionic liquids) at ordinary or high pressures. The scaling constants of pure fluids were easily obtained from a few vapor pressure and density data. Results are compared with other predictive thermodynamic models such as the COSMO-SAC and UNIFAC models. The NRCOSMO model shows particularly promising results in the description of vapor–liquid equilibria of associating mixtures containing CO2.

► A new NRCOSMO is presented as a predictive model.
► NRCOSMO is a very good model for predicting VLE of ionic liquids + CO2 systems.
► Comparisons are made with SRK and PC-SAFT models.