The synergy between Fe and Ru in N2O decomposition over FeRu-FER catalysts: A mechanistic explanation

Fe-FER is an active catalyst for the abatement of N2O in the tail gas of nitric acid plants. The activity of Fe-FER can be increased if Ru is added as a second active component. This is a surprising finding, because noble metals are usually strongly inhibited by NO, which is always present in tail gas. Yet the bimetallic FeRu-FER catalyst is more active than the sum of the components, Fe-FER and Ru-FER. A synergy between Fe and Ru can explain this phenomenon. This work discusses the role of Fe and Ru in the reaction mechanism as well as the interplay of these two components. In situ IR measurements show that the preferential adsorption of NO and its reaction products on Fe in the bimetallic catalyst reduces the inhibiting effect of NO on the Ru component; this effect largely contributes to the synergy between Fe and Ru. Moreover, in situ X-ray absorption data are presented, which allow for tracing the average oxidation state of the two active components Fe and Ru under reaction conditions.