The property tuning of NH3-SCR over iron-tungsten catalyst: Role of calcination temperature on surface defect and acidity

Iron-tungsten composite oxide catalysts have been prepared using a no-water grinding method followed by calcination from 400 to 800 degrees C. Treatment from 400 degrees C to 800 degrees C led to the crystallinity increase and weaker interaction between Fe and W. The catalyst calcined at low temperature (400 degrees C) obtained ample lattice defect, more surface Fe2+ species and surface oxygen and showed the greatest low-temperature catalytic activity. At high calcination temperature, less surface oxygen-vacancies and weak reducibility of samples were found and correspond to decreased catalytic properties. The calcination at 500 degrees C for iron-tungsten catalyst was accompanied by the coexistence of surface defect and FeWO4 or WO3 species with an optimal ratio, prompting its best active window with more than 90% NOx conversion at 220-500 degrees C. More specially, the unsaturated cations (Fe-m + and Wn+) about surface defect gave rise to form more Lewis acid sites, and the O-W-O and W-O-W in connection with hydrated tungsten species led to the formation of BrOnsted acid sites. The reaction intermediate between NO3- and NH2 formed on the surface of FeOx-WO3 catalyst was such a crucial factor in improving the reaction performance of NH3-SCR and the difference of N-2 selectivity.

Automated summary

Iron-tungsten composite oxide catalysts were prepared using a no-water grinding method followed by calcination at different temperatures. The study found that catalysts prepared at low temperatures showed the greatest catalytic activity, while high-temperature calcination led to decreased catalytic properties. Additionally, catalysts calcined at 500 degrees Celsius exhibited the best catalytic performance due to the coexistence of surface defects and specific species, resulting in over 90% NOx conversion in the 220-500 degrees Celsius range.