Low-Temperature Selective Catalytic Reduction of NOx with NH3 over Fe–Mn Mixed-Oxide Catalysts Containing Fe3Mn3O8 Phase

Novel Fe–Mn mixed-oxide catalysts were prepared for the low-temperature selective catalytic reduction (SCR) of NO x with ammonia in the presence of excess oxygen. It was found that Fe(0.4)–MnO x catalyst showed the highest activity, yielding 98.8% NO x conversion and 100% selectivity of N 2 at 120 °C at a space velocity of 30 000 h –1 . XRD results suggested that a new crystal phase of Fe 3 Mn 3 O 8 was formed in the Fe–MnO x catalysts. TPR and Raman data showed that there was a strong interaction between the iron oxide and manganese oxide, which is responsible for the formation of the active center―Fe 3 Mn 3 O 8 . Intensive analysis of fresh, used, and regenerated catalysts by XPS revealed that electron transfer between Fe n + and Mn n + ions in Fe 3 Mn 3 O 8 may account for the long lifetime of the Fe(0.4)–MnO x catalyst. In addition, the SCR activity was suppressed a little in the presence of SO 2 and H 2 O, but it was reversible after their removal.