Platinum as a Catalyst
Exhaust Gas Catalysts
The best known examples are the exhaust purification catalysts for motor vehicles. In most cases here, platinum is used as an active component. Besides the well known three-way catalysts and oxidation catalysts for gasoline and diesel cars, catalysts are now to be found in just about all other motor driven devices and equipment, such as in motor bikes, heavy goods vehicles, building machines, small engines in gardening implements, large stationary engines, and also in boats and yachts. Exhaust gases from industrial processes and chemical plants are also purified over exhaust gas catalysts.
In this type of catalytic purification, the hazardous substances contained in the exhaust gas, e.g. carbon monoxide, hydrocarbons, other organic substances and nitrogen oxides, are converted to carbon dioxide, water and nitrogen.
The active catalyst material (precious metal + support substance) is usually applied to honeycomb ceramic bodies or to metal substrates. The narrow channels of these monoliths permit the intensive contact of the exhaust gas with the catalyst layer that has been applied inside the channels, thus ensuring the effective conversion of the hazardous contents.
Although the high demands on modern exhaust gas catalysts usually require catalyst formulations that are very complex, platinum is an indispensible constituent of the great majority of exhaust gas catalysts.