Activity enhancement of WO3 modified FeTiOx catalysts for the selective catalytic reduction of NOx by NH3

A series of WO3 modified iron-titanate mixed metal oxides catalysts (the molar ratio of Fe/Ti = 4:1) were synthesized by conventional impregnation method and tested for selective catalytic reduction of NOx by NH3. The addition of WO3 species could enhance the catalytic performance of FeTiOx and 6 W/FeTiOx showed optimal activity with above 80 % NO conversion under a wide operating temperature window of 200-400 degrees C. It also exhibited excellent stability in the presence of H2O and SO2 at 250 degrees C, even as low as 225 degrees C, which provided a suitable deNO(x) candidate for stationary sources. The characterization methods including XRD, BET, XPS, H-2-TPR, NH3-TPD, NO-TPD and in situ DRIFTs were used to investigate the structure and surface properties of catalysts and their influence on the catalytic activity. The results demonstrated that the impregnation of WO3 species led to the strong electronic inductive effects between Fe3+ and W6+, Ti4+ and W6+ in the forms of Fe(3+n)+-O-W(6-n)+ and Ti(4+n)+-O-W(6-n)+ structures, increasing the ratio of chemical adsorbed oxygen species, surface OH-, which were stimulative to low-temperature NH3-SCR reaction. The increased amount of surface Bronsted acid sites mainly came from W-OH species. Besides, the reaction pathway over 6 W/FeTiOx mainly followed Eley-Rideal mechanism at 225 degrees C through the reaction between gaseous NO and adsorbed NH3 species.

Automated summary

A series of WO3 modified iron-titanate mixed metal oxides catalysts with optimized activity for high efficiency NO conversion over a wide temperature range have been synthesized. These catalysts show excellent stability in the presence of water and SO2, making them suitable for stationary source deNO(x) applications.