Selective Reduction of NO with NH3 over Various Supported Vanadia Catalysts

摘要

The work described in the paper will concentrate on: (1) the mechanism of the reaction of NO, NH3 and O2 over the monolayer catalyst V2O5 on TiO2, and (2) the development of silica-supported vanadia/titania catalysts for the selective reduction of NOx by ammonia in the presence of an excess of oxygen. The mechanistic work was carried out with the aid of labelled molecules such as (15)NH3, (15)NO and (18)O2. The role of O2 and NH3 is discussed in both a qualitative and a quantitative sense. The results confirm that lattice oxygen participates in the reaction. Water, produced from the reaction involving NO, NH3 and O2, is formed at two sites; the first part comes from the reaction of gaseous nitric oxide and adsorbed ammonia via an Eley-Rideal mechanism; the other part comes from a surface dehydration process. Evidence is given that ammonia does not react with oxygen during the reaction, but that nitrogen and nitrous oxide were produced by a reaction involving all three species: NO, NH3 and O2. Nitrous oxide and water are both formed at different sites of the catalyst.