Simultaneous CO2 and SO2 capture by using ionic liquids: a theoretical approach.

Density functional theory (DFT) methods were used to analyze the mechanism of interaction between acidic gases and ionic liquids based on the 1-ethyl-3-methylimidazolium cation coupled with five different anions. Single ion pairs and ionic clusters containing six ion pairs were used to model the interactions of the ionic liquids with acidic gas molecules. The properties of the systems were analyzed based on geometric properties, interaction energies and Bader's theory. The cluster approach gives a more accurate representation of the behavior of ions and gases in the bulk liquid phase, and despite computational challenges, the cluster approach allows us to quantify interactions beyond short range ones used in the single ion pair-acidic gas model commonly applied in the literature. The results reported herein point out efficient simultaneous capturing of both gases especially for ionic liquids containing the acetate anion.