NO (or NH3) + O2 adsorption on fluorine-doped vanadia/titania and its role in the mechanism of a two-step process characterized by EPR

This study aimed at elucidating a two-step process of the low-temperature selective catalytic reduction (SCR) reaction. The data were collected through studying the EPR signal of NO (or NH3) + O2 adsorption on fluorine-doped vanadia/titania and vanadia/titania catalysts used for SCR reaction, as well as the impact of SO2 and H2O added to the gas mixtures. The EPR experiments provided a new method to explain the SCR reaction, which were associated with NO (NH3) + O2 reacting systems and had been inferred step by step. In summary, the first step of the two-step process was that the vanadium sites were reduced by NO or NH3 as electron donor; then, the superoxide ions appeared over vanadium.The experimental findings showed that the surface acidity, surface oxygen vacancies and the superoxide could be increased by fluorine doping, accordingly, the two-step process rate would be enhanced by F doping. It was the reason for F-doped catalyst had the higher catalytic activity than vanadia/titania. This two-step process could also be used to elucidate the inhibition mechanism of SO2 and H2O for the SCR reaction.

The research used a new method through studying the EPR signal of NO (or NH3) + O2 adsorption on fluorine-doped vanadia/titania and vanadia/titania catalysts, as well as the impact of SO2 and H2O added to the gas mixtures. A two-step process was proposed in the adsorption of reactants over vanadia/titania catalyst, which could be used to elucidate the inhibition mechanism of SO2 and H2O on the SCR reaction. The importance of this two-step process in the mechanism of low-temperature NH3-SCR over F-doped vanadia/titania catalyst was revealed.Figure optionsDownload as PowerPoint slideHighlights
► The enclosed manuscript has investigated the adsorption of reactants over the F-doped catalysts by EPR, which led to the finding of a two-step process in the adsorption.
► It is a new method to investigate this two-step process through studying EPR.
► This study will advance the knowledge about the affecting pattern of H2O and SO2 on the low-temperature SCR over the F-doped vanadia/titania catalyst, as well as the character of the two-step process in this affecting pattern.