(742c) Molecular Simulation Investigation of Pure and Mixed Gas Absorption in a Non-Ideal Binary Ionic Liquid Mixture

Ionic liquids (ILs) are novel environmentally benign solvents comprised only of ions and are attractive candidates for replacement of volatile organic compounds used in chemical industry due to their non-volatile nature. One of the widely studied research topics in the field of ILs is to use their difference in ability to absorb polar and nonpolar substances such as carbon dioxide (CO₂) or methane (CH₄), owing to their amphiphilic nature, for gas separation purposes. The knowledge of gas mixture solubility in ILs at high pressures, which becomes relevant in applications such as tertiary oil recovery and landfill gas utilization, is critical for the design. A large repertoire of ionic liquids has been designed leveraging the observation that the pure gas solubility is governed by the anion identity and ionic liquid free volume. However, in this study, we take a different approach of ionic liquid mixtures in tuning the gas solubility. Our work is guided by the hypothesis that the presence of non-native structures in binary IL mixtures will translate into nonideality in both pure and mixed gas solubilities, which can be used for efficient separation. Although the presence of non-ideality in the pure gas solubilities in IL mixture has been reported previously, in this presentation we provide a molecular level interpretation of this behavior. We also evaluate the validity of ideal gas solubility selectivity in IL mixtures. The focus of this study will be on solubility of CO₂, CH₄and their mixtures in binary IL mixtures containing common cation 1-n-butyl-3-methylimidazolium and different anions, namely, chloride and bis(trifluoromethanesulfonyl)imide as a function of molar composition at 353 K. The results of the Henry’s law constants of CO₂and CH₄ along with single and binary component gas absorption isotherms obtained from Gibbs ensemble Monte Carlo simulations will be presented.