Efficient capture of benzene and its homologues volatile organic compounds with π electron donor-based deep eutectic solvent: Experimental and computational thermodynamics

Abstract

π-electron donor-based deep eutectic solvents (DESs) were proposed to enhance the absorption of benzene, toluene, ethylbenzene, xylene (BTEX). The gas absorption performance of π-electron donor-based DESs for BTEX were systematically studied by computational thermodynamics combined with gas absorption experiments. COSMO-RS model was implemented to obtain the solvent capacity of BTEX in 182 DESs (i.e., 13 HBDs and 14 HBAs) to screen out potential excellent absorbents. In addition, the selected HBA, HBD and BTEX were analyzed by σ-profiles to preliminarily determine the interaction between molecules. The absorption properties of BTEX in DESs were measured. The results showed that the DES tetrabutylammonium bromide (TBAB) + benzoic acid (BA) (1:3) had the highest absorption capacity for BTEX in all DESs studied in this work (e.g. 0.911 g benzene/g at 298.15 K). Molecular dynamics simulations were performed to explore the diffusion behavior of gas in DESs. The free volume of DESs-gas blends gradually decreases with the increase of aromatics branched chains, and the mean square displacement shows the same trend. This indicates that aromatics without branched chains are easier to diffuse in DESs. Non-bond interaction analysis shows that electrostatic interaction and π-π interaction are the main interactions. In addition, the direct reason for the enhancement of BTEX absorption by π-electron donors is to enhance the X (O, C)-H···π interactions between DES and BTEX, and increase the additional π-π interaction with BTEX.