Effect of NO upon N ₂O decomposition over Fe/ZSM-5 with low iron loading

An Fe/ZSM-5 catalyst with a very high Si/Al ratio was prepared, and using it, the effect of NO upon the kinetics of N ₂O decomposition was studied. The addition of small, nonstoichiometric amounts of NO was observed to cause the rate to increase by more than an order of magnitude. The kinetics were well-fit by a rate expression that was first order in the partial pressure of N ₂O for the situation without added NO and separately for the situation where NO was added. The Arrhenius parameters of the rate coefficient differed for the two situations. The results are consistent with a mechanistic scheme wherein the reaction proceeds via an oxide-oxo redox cycle in the absence of NO. The results suggest that the NO-assisted decomposition of N ₂O does not require a second iron site adjacent to the active site and that NO _x species adsorbed on the same cation site could serve as locations for oxygen storage if, in fact, the promotional effect of NO is related to such storage.