Mechanism of the Reaction of Nitric Oxide, Ammonia, and Oxygen over Vanadia Catalysts. 2. Isotopic Transient Studies with Oxygen-18 and Nitrogen-15

Article abstract of DOI:10.1021/j100311a016

The mechanism of nitric oxide reduction with ammonia to form N2, H2O, and N2O both in the presence and in the absence of O2 over the following series of catalysts, unsupported V2O5, V2O5 on TiO2, V2O5 on SiO2/Al2O3, and V2O5 on Al2O3, has been investigated with the aid of labeled O2 and labeled NH3 at 400 deg C.The behavior of ammonia was studied both in the presence and in the absence of O2.The presence of labeled O2 gives extra information about the product distribution and the reaction mechanism.Evidence is given that ammonia does not react with O2 or O from any source during the reaction, but that nitrogen and nitrous oxide were produced by a reaction involving all three species, NO, NH3, and/or O2.Nitrous oxide and water are both formed at two different sites of the catalyst.A series of transient tracing studies were performed in a plug-flow reactor using (15)NH3 and (18)O2.Both (15)NN and (15)NNO were produced on the unsupported V2O5, V2O5 on TiO2, V2O5 on SiO2/Al2O3, and V2O5 on Al2O3 with very high selectivities.The mechanism of the reaction of NO, NH3, and O2, proposed in a previous paper (ref 2), is further evaluated on the basis of this new experimental evidence.