Low-temperature selective catalytic reduction of NO with NH3 over iron and manganese oxides supported on titania

A series of catalysts of manganese oxide supported on TiO2 and iron–manganese oxide supported on TiO2 with different amounts of manganese and iron were studied for low-temperature selective catalytic reduction (SCR) of NO with ammonia in the presence of excess oxygen. It was found that the addition of iron oxide not only increased the NO conversion and N2 selectivity but also increased the resistance to H2O and SO2. The Fe–Mn/TiO2 catalysts yield high activities and high N2 product selectivity. The N2O product selectivity increased with the amount of MnOx as well as temperature. Crystalline phase of MnOx was present at ≥15% Mn on TiO2, and the amount increased with Mn content. In addition, SO2 and H2O decreased the activities only slightly, while such effect was reversible. The Fe–Mn/TiO2 with Mn/Fe=1 showed the highest activity. The results showed that this catalyst yielded nearly 100% NO conversion at 120 °C at a space velocity of 15,000 h−1. The effect of oxygen was also studied. Reversible transient behaviors similar to that on other oxide catalysts, including vanadia and chromia, were observed for the Fe–Mn/TiO2 catalyst.