Modified COSMO‐UNIFAC model for ionic liquid–CO2 systems and molecular dynamic simulation

Abstract A new predictive molecular thermodynamic model (i.e., modified COSMO‐SAC‐UNIFAC) was first proposed and extended to predict the solubility of CO 2 in pure and mixed ionic liquids (ILs) at the temperatures down to 263.2 K. It is interesting to discover that with equimolar amounts, the solubility of CO 2 in such 1:1 IL pairs, that is, [A 1 ][B 1 ] + [A 2 ][B 2 ] and [A 1 ][B 2 ] + [A 2 ][B 1 ], was consistent at the same temperature and pressure in the case of exchanging their respective cations and anions. The molecular dynamic (MD) simulation for CO 2 + mixed ILs was performed to deeply analyze and explain this intriguing phenomenon. Not only the CO 2 gas drying experiment with the ILs ([C2mim][OAc], [C2mim][dca], and [C2mim][OAc] + [C2mim][dca]) as absorbents but also the corresponding process simulation and optimization were made to stress the effectiveness and applicability of the new thermodynamic model. Thus, this work ranges from molecular level to systematic scale.