Nitrate Doping for SO₂ Resistance Enhancement of Solid Sorbents Made from Polyamine-Based Protic Ionic Liquid-Functionalized Mesoporous Silica

Abstract

Flue gas from coal-fired power plants often contains SO 2 even after desulfurization, the existence of which can dramatically reduce the adsorption of CO 2 with amine-based solid sorbents. To tackle this challenge, a new sorbent, polyaminebased protic ionic liquid-functionalized mesoporous silica, was developed by doping nitrate into triethylenetetramine. The dynamic CO 2 adsorption/desorption experiments under 500 ppm SO 2 show that the CO 2 adsorption capacities of the nitratecontaining 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 SO 2 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 SO 2 and the secondary amine −N(2)H decrease by 6.3 and 22.1%, respectively. In addition, the experimental results from Fouriertransform infrared spectroscopy demonstrate that nitrate inhibits the reaction between amine groups and SO 2 to form sulfonamides.