(192i) Pure and Mixed Gas Absorption in Nonideal Binary Ionic Liquid Mixtures, a Molecular Simulation Study

Ionic liquids (ILs) are novel chemical substances composed entirely of ions and are attractive candidates for replacement of volatile organic compounds used in chemical industry. One of the widely studied research topics in the field of ILs is their ability to absorb polar substances such as carbon dioxide (CO₂) and sulfur dioxide (SO₂) owing to their ionic nature. At the same time, conventional ILs exhibit rather poor solubility for nonpolar substances such as alkanes. A large repertoire of ionic liquids has been designed given that the solubility is governed by the anion identity and ionic liquid free volume. 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 positive deviation in the excess molar volume will translate into nonideality in gas solubility. This study focuses on bulk fluid solubility of CO₂, SO₂ and CH₄ and their mixtures in two sets of binary IL systems: (a) 1-n-butyl-3-methylimidazolium [C₄mim]⁺, chloride Cl^- and bis(trifluoromethanesulfonyl)imide [NTf₂]^- and (b) [C₄mim]⁺ , Cl^- and trifluoroacetate [CF₃COO]^- as a function of temperature. The choice of ionic components was influenced from our prior work suggesting that these ionic liquid systems are characterized by small yet positive excess molar volumes independent of the temperature. We will present the results of the Henry’s law constants along with single and binary component gas absorption isotherms.