Design of multiple-site imidazole derivative aqueous solution for SO2 capture in low concentration

In this work, a novel strategy was reported for improving SO 2 capture through multiple-site interactions of N-imidazole derivative. The tris (2-(1-H-imidazole-1-y1)ethyl) amine (TIA) was designed, synthesised and mixed with water to form the mixed absorbents for SO 2 absorption. The physical properties were determined and the mixed absorbents exhibited low densities and viscosities, which are beneficial to the mass and heat transfer. The SO 2 absorption reached equilibrium rapidly within 60 s and as high as 2.09 mol SO 2 per mol TIA could be absorbed at low SO 2 concentration (<2 kPa). With increasing the mass ratio of TIA in the aqueous absorbents to 50%, more than 6.2 mol/kg absorbent absorption performance was obtained. The desorption was carried out at 80 °C and the recycling performance was excellent without any change during 5 cycles. High SO 2 /CO 2 selectivity was achieved due to the suitable basicity of the absorbents. In addition, the absorption mechanism was established and proved by FTIR and 1 H NMR. Thermodynamic analysis was determined using gPROMS, which suggested the pK a of the TIA varied in a proper range for SO 2 capture. Overall, the novel mixed absorbents with excellent physical properties and high SO 2 absorption capacity have much potential for flue gas desulfurization.