Efficient Recovery of Dichloromethane from Tail Gas by 1-Alkyl-2-ethylimidazole Ethyl Sulfate and 1-Ethylpyridine Ethyl Sulfate

Four sulfate-based ILs, 1-butyl-3-ethylimidazolium ethyl sulfate [Beim][EtSO4], 1-ethyl-3-ethylimidazolium ethyl sulfate [Eeim][EtSO4], 1-ethyl-3-methylimidazolium ethyl sulfate [Emim][EtSO4], and 1-ethylpyridinium ethyl sulfate [Epy][EtSO4], were synthesized and used as an absorbent for dichloromethane (DCM). Among them, the maximum DCM absorption capacity of 0.426 g DCM g–1 IL was achieved in [Beim][EtSO4] at 313.15 K and 37.7% DCM concentration, which was 42.2% higher than that of common organic solvent bis(2-ethylhexyl) adipate under the same conditions. The density and viscosity of [Beim][EtSO4] containing different mass fractions of DCM were measured. The density of [Beim][EtSO4] increases with the mass fraction of adsorbed DCM, while the viscosity decreases sharply. The efficient performance of ILs to absorb DCM is mainly due to the hydrogen bonding interaction between the anion and DCM, which was confirmed by spectroscopic measurement and quantum chemical calculations. This work demonstrates the great potential of ILs in separating and recovering DCM from exhaust gas.