Accurate modeling of supercritical CO₂ for sustainable processes: Water + CO₂ and CO₂ + fatty acid esters mixtures

Supercritical fluid technology has allowed significant improvements in several industrial processes, and there are still many opportunities for further applications in new emergent areas. This contribution provides some perspectives on drivers and opportunities for new or advanced applications of supercritical fluids, including the search for sustainable processes and healthy products. It also addresses some of the needs, such as using refined modeling tools with a specific treatment taking into account the long range fluctuations in the density (or composition for the case of mixtures) as one approaches the critical point to accurately design the process in this region. New results are presented on the application of the crossover soft-SAFT equation of state to two motivating systems involving supercritical CO₂, the CO₂-water mixture and the solubility of supercritical CO₂ in fatty acid esters. Both systems are challenging from a modeling perspective as they are highly non-ideal. Crossover soft-SAFT gives very accurate results, compared to available experimental systems, for the CO₂-water mixtures. The equation is also able to predict the critical line in quantitative agreement with experimental data with one constant binary parameter, being a step forward in modeling the behavior of this mixture. The equation also gives excellent results when modeling the solubility of supercritical CO₂ in fatty acid esters, with two binary parameters, independent of the temperature and composition, in this case.