Microscopic poisoning mechanism of heavy metals on the deNOx over the β-MnO2 catalyst

Abstract

Mn-based catalysts are promising materials for the removal of NOx by NH3-SCR reaction. Heavy metals can cause the deactivation of deNOx of catalysts. However, the inactivation mechanism of catalysts requires further research. In this paper, the effects of Pb and Zn doping on the deNOx reaction over the β-MnO2 catalyst were investigated by the DFT method, and the poisoning mechanism of heavy metals on the catalyst was revealed. Pb and Zn can not only inhibit the adsorption of NH3 and O2 at the peripheral sites, but also weaken the adsorption properties of NH3 at the doping sites, leading to a decrease in the activity of the β-MnO2 catalyst. Meanwhile, Pb and Zn can limit the formation and decomposition of *NH2NO intermediates, which is detrimental to the SCR reaction. In addition, the production of hydroxyl groups is restricted due to Pb and Zn preventing the formation of *H and *O. Although Pb and Zn can make the conversion of hydroxyl groups to *H2O easier, it is not enough to compensate for the restricted *H2O generation caused by the large reduction in the number of hydroxyl groups, and the deNOx reaction is ultimately inhibited.