The catalytic oxidation of ammonia over platinum or platinum-rhodium catalysts is a crucial reaction for both the manufacture of nitric acid and in the catalytic exhaust gas after treatment systems for lean burn engines (e.g.with Diesel and natural gas fuels).In the first application, the oxidation of NH3 to NO is carried out industrially using a gauze catalyst composed of an alloy of platinum and rhodium.This design gives relatively short contact times between the reactant stream and the catalyst.