Nitrate Doping for SO₂Resistance Enhancement of Solid Sorbents Made from Polyamine-Based Protic Ionic Liquid-Functionalized Mesoporous Silica

Flue gas from coal-fired power plants often contains SO2 even after desulfurization, the existence of which can dramatically reduce the adsorption of CO2 with amine-based solid sorbents. To tackle this challenge, a new sorbent, polyamine-based protic ionic liquid-functionalized mesoporous silica, was developed by doping nitrate into triethylenetetramine. The dynamic CO2 adsorption/desorption experiments under 500 ppm SO2 show that the CO2 adsorption capacities of the nitrate-containing sorbent almost remain invariant after 11 adsorption/desorption cycles, but the adsorption capacities of the sorbent without nitrate decrease by 50.9%. The significant improvement in SO2 resistance of the nitrate-containing sorbent was further explained with density functional theory calculation, which reveals the binding energy and net charge transfer amounts between SO2 and the secondary amine-N(2)H decrease by 6.3 and 22.1%, respectively. In addition, the experimental results from Fourier-transform infrared spectroscopy demonstrate that nitrate inhibits the reaction between amine groups and SO2 to form sulfonamides.