Efficient SO<sub>2</sub> Absorption by Anion-Functionalized Deep Eutectic Solvents
Ge Cui, Dezhong Yang, Hongbin Qi
Abstract
In this work, the anion-functionalized deep eutectic solvents (DESs) comprising solid organic salt tetraethylammonium tetrazolate ([N2222][Tetz]) and ethylene glycol (EG) at a molar ratio 1:2 were synthesized to capture SO2. DESs [N2222][Tetz]-EG(1:2) could capture 0.853 g of SO2/g solvent (4.31 mol SO2/mol solvent) at 1.0 atm and 20 °C. Interestingly, [N2222][Tetz]-EG(1:2) exhibited a high SO2 absorption capacity of 0.140 g of SO2/g solvent (0.708 mol SO2/mol solvent) at 2000 ppm, which was much higher than the absorption capacity (0.002 g of SO2/g solvent or 0.009 mol SO2/mol solvent) of non-functionalized DESs consisting of tetraethylammonium chloride ([N2222][Cl])-EG(1:2) under the same conditions. Moreover, [N2222][Tetz]-EG(1:2) can be reused and showed good reversibility. Nuclear magnetic resonance and Fourier transform infrared results indicated that the high SO2 absorption capacity of [N2222][Tetz]-EG(1:2) was due to the chemical reaction between SO2 and anion [Tetz]−, and the SO2 absorption enthalpy of [N2222][Tetz]-EG(1:2) was −52.7 kJ/mol which also confirmed the strong interaction between SO2 and [N2222][Tetz]-EG(1:2).