Vinyl chloride capture by ionic liquids: Structural effects and molecular thermodynamic insights

Abstract

Ionic liquids (ILs) have been proposed as potential environmentally friendly and efficient solvents for gas absorption and purification. In this study, we propose the utilization of ILs for vinyl chloride (VC) capture. The structural effects, including the cationic skeleton and alkyl chain length on the cation, as well as the anionic structures such as alkyl chain length for phosphate and sulfate anions and the fluorination effect, were systematically investigated at a microscopic level using COSMO-RS mode and quantum chemical calculations. ILs screening results reveal that noncyclic cationic skeletons with long alkyl chains on both cations and phosphate/sulfate-based anions, without fluorinated derivatives, are favorable for VC absorption due to their large fractional free volume and nonpolar nature. Both the anion and cation contribute to the absorption process; however, the anion effect plays a more significant role. The interaction between VC and the cation is mainly governed by van der Waals forces, while both hydrogen bonding interactions and van der Waals forces exist between VC and the anion.