New insight on optimization of acid promoter over Fe/Zr catalyst for selective catalytic reduction of NOx with NH3

MoO3 and WO3, as acidic promoter, were widely used in the modification of vanadium based and vanadium-free based catalysts, which could significantly ameliorate the catalytic performance of the catalysts. In this work, the effects of MoO3 and WO3 on the selective catalytic reduction (SCR) performance of Fe/Zr catalyst were studied, and the role of acidic promoters was clarified. The results indicated that MoO3 and WO3 could improve the catalytic activity of Fe/Zr catalyst in the entire reaction temperature range. Noteworthy, Fe/Zr-W catalyst exhibited the highest SCR catalytic activity, and the NOx conversion rate achieved nearly 100% at 250 degrees C. The characterization results suggested that the promoting effect of WO3 on catalytic performance of Fe/Zr catalyst might be due to the improvement of redox property and surface acidity, higher Fe3+/(Fe2++Fe3+) ratio and abundant surface chemisorbed oxygen. The in-situ DRIFTS experiments indicated that both E-R and L-H mech-anisms were obeyed on Fe/Zr-W catalyst, while only E-R mechanism was obeyed on Fe/Zr and Fe/Zr-Mo cat-alysts in the NH3-SCR reaction at 250 degrees C. This study might provide an alternative development of high-performance vanadium-free catalyst for NOx abatement.