The activity of supported vanadium oxide catalysts for the selective reduction of NO with ammonia

The activities of monolayer V2O5 catalysts for the selective reduction of NO with NH3 are compared with those of commercial available catalysts containing V and/or W. From steady state and pulse experiments it can be concluded that the reduction of surface sites proceeds either by NH3 + NO or by NH3 alone. The reoxidation of the reduced sites occurs by gaseous oxygen or NO. The experimental reaction stoichiometry can be explained in terms of suitable combinations of these four reactions

Mechanism of the reaction of nitric oxide, ammonia, and oxygen over vanadia catalysts: 2. Isotopic transient studies with oxygen-18 and nitrogen-15

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°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 15NH3 and 18O2. Both 15NN and 15NNO 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