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

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 N-2 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 W-O-Fe bonds, the oxidation ability of surface Fe(3+delta)+ 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 N-2 selectivity simultaneously. Besides, the deposited WOx species could also supply abundant surface reactive Lewis and Bronsted 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 deNO(x) process on diesel engines.