Study on the mechanism of selective catalytic reduction with propylene (C3H6-SCR) on the MnOx-based catalysts by a doping experiment and DFT+U calculation

Abstract

For a long time, the research of the C3H6-SCR reaction relied only on experimental techniques, which limited the recognition of the mechanism for this process. Herein, we systematically calculated the adsorption characteristics, electronic structure, oxidation pathways, and reaction pathways of the C3H6-SCR procedure by density functional theory (DFT) based on a representative doping model. DFT calculations show that the C3H6 oxidation with NO to CH3NO2/CH3CN is more favorable to achieve energetically than CH3NO/CH3NCO, while the NO2 is a better oxidant than O2 and NO for the C3H6 oxidation at low temperatures. The excellent correlation between temperature programmed experiment and the C3H6-SCR reaction path barrier can reasonably conclude that the first step oxidation of C3H6 and the formation of amino intermediates(−NH2) are the keys to the low-temperature activity of C3H6-SCR. Besides, the stronger charge non-localization on the surface with lanthanum doping demonstrated by XPS could be responsible for the enhanced oxidation of the active sites, hence promoting NO to NO2. The study shed more light on the C3H6-SCR reaction mechanism at the molecular level and expects to contribute to the development of low-temperature C3H6-SCR.