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

Abstract

In this work, a novel strategy was reported for improving SO2 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 SO2 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 SO2 absorption reached equilibrium rapidly within 60 s and as high as 2.09 mol SO2 per mol TIA could be absorbed at low SO2 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 SO2/CO2 selectivity was achieved due to the suitable basicity of the absorbents. In addition, the absorption mechanism was established and proved by FTIR and 1H NMR. Thermodynamic analysis was determined using gPROMS, which suggested the pKa of the TIA varied in a proper range for SO2 capture. Overall, the novel mixed absorbents with excellent physical properties and high SO2 absorption capacity have much potential for flue gas desulfurization.