Highly Efficient, Reversible, and Selective Absorption of SO 2 in 1-Ethyl-3-methylimidazolium Chloride Plus Imidazole Deep Eutectic Solvents

The capture of SO 2 from industrial tail gas is of great significance to control air pollution and reserve sulfur resource. In this work, we proposed the use of deep eutectic solvents (DESs) formed by 1-ethyl-3-methylimidazolium chloride ([emim]Cl) and imidazole for SO 2 capture, considering the strong electron-donating ability of Cl – in [emim]Cl and the weak basicity of tertiary N in imidazole. Both components should exhibit strong interaction with SO 2, which is electron-deficient and Lewis acidic. The SO 2 capture performance of [emim]Cl+imidazole DESs was thus investigated systematically by both pure gas and mixed gas absorption experiments. It is found that highly efficient absorption of SO 2 can be achieved in DESs. The SO 2 absorption capacities reach as high as 19.15 mol/kg at 101.3 kPa and 5.73 mol/kg at 2.0 kPa, exceeding most other solvents reported in the literature. The DESs also display good reversibility and excellent selectivity for SO 2 absorption, which is rather important for practical SO 2 capture applications. Moreover, the mechanism of SO 2 absorption was analyzed by quantum chemistry calculations and spectroscopic characterizations.