The smart surface modification of Fe2O3 by WOx for significantly promoting the selective catalytic reduction of NOx with NH3

Abstract

The deposition of WOx species using conventional impregnation method is a very simple and efficient way to adjust the surface acidity and redox ability of hematite Fe2O3 simultaneously, significantly improving its catalytic activity and N2 selectivity for the selective catalytic reduction of NOx with NH3 (NH3-SCR). The deposited WOx species on Fe2O3 surface was in highly unsaturated coordination state acting as an effective surface modifier. Through the electronic inductive effect in WOFe bonds, the oxidation ability of surface Fe(3+δ)+ species was well increased, yet the over-oxidation of NH3 on bulk Fe2O3 was significantly suppressed, which was quite beneficial to the improvement of NH3-SCR activity and N2 selectivity simultaneously. Besides, the deposited WOx species could also supply abundant surface reactive Lewis and Brønsted acid sites for NH3 adsorption and activation during the SCR reaction. The NH3-SCR process on this WOx/Fe2O3 catalyst mainly followed an Eley-Rideal (E-R) reaction pathway between gaseous NO and active NH3 adsorbed species, which was the main reason for its superior SO2 resistance. This opens a new route for the preparation of highly efficient, selective, cost effective and SO2 resistant NH3-SCR catalysts for the deNOx process on diesel engines.