Low-temperature selective catalytic reduction of NO with NH 3 over iron and manganese oxides supported on titania

Abstract

A series of catalysts of manganese oxide supported on TiO 2 and iron–manganese oxide supported on TiO 2 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 N 2 selectivity but also increased the resistance to H 2O and SO 2. The Fe–Mn/TiO 2 catalysts yield high activities and high N 2 product selectivity. The N 2O product selectivity increased with the amount of MnO x as well as temperature. Crystalline phase of MnO x was present at ≥15% Mn on TiO 2, and the amount increased with Mn content. In addition, SO 2 and H 2O decreased the activities only slightly, while such effect was reversible. The Fe–Mn/TiO 2 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/TiO 2 catalyst.