Oxidation catalysts are mainly used in diesel engines for the reduction of pollutant emissions. The conversion of the pollutants into CO2 and water takes place on the precious metal coating of the catalyst.
In contrast to the 3-way principle, there is a surplus of air in diesel exhaust gas, referred to as lean exhaust. This means that NOx cannot be converted to nitrogen on an oxidation catalyst. Instead, at temperatures of 150 - 400 °C, NO is oxidized to NO2.
Furthermore, the exhaust of a diesel engine is generally considerably cooler than that of a gasoline engine. This means that the working temperature of the catalyst has greater significance in the oxidation catalyst, for the catalyst only becomes active above a certain temperature. Frequent changes in temperature and deposits of engine oil and fuel additives push this working temperature to higher levels and the catalyst ages.
Catalyst coatings of Heraeus for oxidation catalysts permit a low working temperature with good resistance to ageing. With our special expertise a low precious metal loading is achieved. Furthermore the more economical palladium can be substituted for the expensive platinum which results in a cost saving. This has no influence on the performance of the catalyst.
Depending on the design of the coating, the oxidation of the NO can be increased or also almost completely suppressed. This makes it possible to design application-specific catalysts to customer requirements. Contact us.