Ether-Linked Diamine Carboxylate Ionic Liquid Aqueous Solution for Efficient Absorption of SO2

Ionic liquids (ILs) as promising absorbents for SO2 capture in flue gas desulfurization have been extensively studied. In this work, a multisite absorption strategy was used to synthesize ether-linked diamine protic ionic liquids (EDPILs) for efficient SO2 capture. The prepared EDPILs containing ether-linkage chain exhibited superior SO2 absorption relative to conventional protic ionic liquids (PILs). Density functional theory calculations demonstrated that the ether-linkage chain intensified the physical interaction between EDPILs and SO2. In a subsequent experiment, bis(2-dimethylaminoethyl) ether dilactate [BDMAEE][L]2, which possessed outstanding SO2 capture capacities, was used to prepare aqueous solutions (aq), which reduced viscosity of PILs and improved their applicability. An in-depth assessment of the desulfurization performance of [BDMAEE][L]2 aq revealed that effective SO2 absorption can be achieved even at relatively low concentrations. Specifically, 50 wt % [BDMAEE][L]2 aq exhibited a high absorption capacity (1.04 molSO2/molILs, 0.097 gSO2/gabsorbents) as well as a high SO2/CO2 selectivity at 0.2 vol % SO2 and 40 °C. Overall, ether-linked absorbents with improved desulfurization performance (high SO2 absorption capacity, satisfactory SO2 removal efficiency, and excellent reusability) possess good application prospects in flue gas desulfurization.