The effects of manganese precursors on NO catalytic removal with MnOx/SiO2 catalyst at low temperature

Abstract

The low-temperature catalytic NO removal efficiencies of catalysts with two different manganese precursors, manganese acetate (αMA catalyst) and manganese nitrate (αMN catalyst), were compared and studied. The NH3-SCR of NO tests using these catalysts were carried out in a self-made reaction device to measure the catalytic activity of the catalysts. Moreover, the reaction pathway analysis of NH3-SCR of NO on the surface of MnO2/SiO2 catalyst and Mn2O3/SiO2 catalyst were performed based on DFT calculations individually. The experimental results show that the NO conversion of αMN catalyst is higher than the αMA catalyst at low temperature (< 180 °C). Besides, the XRD test shows that the main crystal phase is MnO2 for αMN catalysts, and Mn2O3 for αMA catalyst, and the XPS characterization exhibits that the αMN catalyst has the highest MnO2/Mn2O3 ratio. Moreover, DFT calculations indicate that the decompositions of NH2NO and NHNO are the rate determining steps in the whole NH3-SCR of NO process and the decomposition activation energy of NH2OH and NHNO on MnO2 is lower than that on Mn2O3. This is the main reason for the higher NO conversion of catalyst prepared with manganese nitrate as precursor at low temperature.