Developing Electrolyte Perturbed-Chain Statistical Associating Fluid Theory Density Functional Theory for CO2 Separation by Confined Ionic Liquids C

The electrolyte perturbed-chain statistical associating fluid theory (ePC-SAFT) classical density functional theory (DFT) was developed to describe the behavior of pure ionic liquid (IL) and CO₂/IL mixture confined in nanopores, in which a new ionic functional based on the ionic term from ePC-SAFT was proposed for electrostatic free-energy contribution. The developed model was verified by comparing the model prediction with molecular simulation results for ionic fluids, and the agreement shows that the model is reliable in representing the confined behavior of ionic fluids. The developed model was further used to study the behavior of pure IL and CO₂/IL mixture in silica nanopores where the IL ions and CO₂ were modeled as chains that consisted of spherical segments with the parameters taken from the bulk ePC-SAFT. The results reveal that the nanoconfinement can lead to an increased CO₂ solubility, and the solubility increases with increasing pressure. The averaged density of pure IL and solubility of CO₂ are strongly dependent on pore sizes and geometries. In addition, the choice of IL ions is very important for the CO₂ solubility. Overall, the modeling results for silica-confined systems are consistent with available molecular simulation and experimental results.