Deep removal of chlorobenzene based volatile organic compounds from exhaust gas with ionic liquids

Taking chlorobenzene (C6H5Cl) and o-dichlorobenzene (C6H4Cl2) as representatives of chlorobenzene based volatile organic compounds (CBs), a novel deep-purification technology of absorbing with ionic liquids (ILs) as absorbent was proposed and systematically investigated. Based on conductor-like screening model for real sol-vents (COSMO-RS) model, the suitable IL 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) for absorbing CBs was screened out from 289 kinds of commonly used ILs. Removal experiments of C6H5Cl and C6H4Cl2 by [EMIM][BF4] were carried out at different temperatures, pressures and IL flow rates. Results sug-gested that [EMIM][BF4] had excellent absorption properties, and deep removal of CBs can be achieved that the content of C6H5Cl/C6H4Cl2 in the purified gas can be decreased down to 13.6 ppm/9.9 ppm (in molar fraction). Absorption capacity of [EMIM][BF4] to CBs was almost unchanged after absorbing and desorbing for up to 20 times, proving the repeatability of the absorption performance. Characterization by NMR and FT-IR showed that there was no chemical bond formed between [EMIM][BF4] and CBs, proving that the absorption process was physical absorption. Moreover, the structure of the regenerated [EMIM][BF4] had not been changed, which indicates that [EMIM][BF4] has strong thermal stability and chemical stability. Finally, the interaction mecha-nisms between [EMIM][BF4] and CBs were clarified from the aspects of interaction energy and interaction sites by quantum chemical calculation and wave function analysis. This work fills the gap of removing CBs by ab-sorption method with ILs, and proved that ILs could be employed as promising green solvents for chlorobenzene based VOCs removal.