Promotional mechanism of WO3 over RuO2-Fe2O3 catalyst for NH3-SCO reaction

The promoting effects of WO3 on RuO2-Fe2O3 catalyst were systematically investigated for the selective catalytic oxidation of ammonia to nitrogen. It was found that the introduction of 5 wt.% WO3 led to a dramatic promoting effect on the high-temperature N-2 selectivity of RuO2-Fe2O3 catalyst, giving 100% NH 3 conversion at 250 degrees C and 94% N-2 selectivity at a high temperature of 400 degrees C. In depth analysis using XRD, Raman and H-2-TPR revealed that the addition of WO3 into the RuO2-Fe2O3 catalyst could strongly inhibit the crystallinity of Fe2O3 and decrease the reducibility of RuO2-Fe2O3 catalyst, which were related to the strong interaction between WO3 and Fe2O3. Moreover, in situ DRIFTS studies illustrated that the ammonia oxidation over 1RuO(2)-5WO(3)-Fe2O3 catalyst followed the iSCR mechanism, involving the oxidation of NH 3 into NO species and the reaction of -NH 2 with in situ-formed NO to form N-2. The introduction of WO 3 not only promoted the formation of more acid sites on the catalyst surface but also restrained the formation of nitrate species at high temperature, with few NO2 formed, which contributed to the high N-2 selectivity.