Highly synergistic effects of Fe-W catalysts to enhance medium-low temperature NH3-SCR activity

In this study, we investigated the effects of diffirent tungsten additions on the NH3-SCR activities of iron-based catalysts at medium-low temperatures. By comparing the denitration activity, it was found that the catalyst with 20 % tungsten addition (Fe8W2) was determined to have the best denitration activity at medium-low temperatures, and the catalysts' NOx conversion was more than 80 % in the temperature range of 225-475 degrees C. Combined with the activity analysis and characterization results, both the WO3-Fe2O3 composite and its entry into the Fe2O3 lattice can effectively promote FeOx dispersion and surface species activation, improving FeOx's redox properties. Meanwhile, WO3 and Fe2O3 compound to form FeWOx, and the content of this species is closely related to the medium-low temperature NH3-SCR activity of the catalyst. The results of XPS and H2-TPR indicated that the formation of FeWOx was conducive to the production of more active O species and Fe3+ on the catalyst surface, which may be related to oxygen defects on Fe2O3 and WO3 surfaces caused by Fe-W synergy and the formation of bridged oxygen in Fex+-On--W6+. In addition, the NH3-TPD results show that the generation of FeWOx can also significantly increase the number of acid sites on the catalyst surface. Fe-W synergy facilitates the formation of Fe-O-W bonds and uncoordinated saturated Fex+, creating more Br & oslash;nsted and Lewis acid sites. This increases the catalyst's capacity to adsorb and activate NH3 species.