Absorption of dichloromethane in deep eutectic solvents: Experimental and computational thermodynamics

A series of benzyl-based deep eutectic solvents (DESs) were successfully prepared and used for the capture of condensable dichloromethane gas. The COSMO-RS model was implemented to screen out the appropriate absorbent (i.e., DES TEBAC-TEG) for capturing dichloromethane. The physical properties of density and viscosity of DESs were measured to prove the feasibility of industrial application. The result of absorption experiment shows that TEBAC-TEG (the molar ratio 1:3) has big capacity of 581.72 mg/g with DCM partial pressure of 50 kPa at 303.15 K, and the removal ratio of dichloromethane reached 91.65 %. Further, the absorption mechanism was revealed by Gibbs free energy analysis and quantum chemical calculations. It was found that both chloride ion and TEG displayed high hydrogen bond (HB) acceptance ability, which could form HB with dichloromethane to enhance the absorption process. Particularly, the C-H...pi interaction is dominant between TEBA cation and dichloromethane molecule.