Catalytic Converter: Description and Operation

Generic Catalyst and Exhaust System:

Catalyst and Exhaust System Overview
The catalytic converter and exhaust systems work together to control the release of harmful engine exhaust emissions into the atmosphere. The engine exhaust gas consists mainly of nitrogen, carbon dioxide and water vapor. However, it also contains carbon monoxide, oxides of nitrogen, hydrogen, and various unburned hydrocarbons, which are major air pollutants and their emission into the atmosphere has to be controlled.

Three Way Catalytic Converter
A catalyst is a material that remains unchanged when it initiates and increases the speed of a chemical reaction. A catalyst will also enable a chemical reaction to occur at a lower temperature. The TWC contains a catalyst in the form of a specially treated honeycomb structure saturated with catalytically active precious metals (either platinum and rhodium, or palladium and rhodium). The TWC catalyzes the oxidation reactions of unburned hydrocarbons and carbon monoxide and the reduction reaction of oxides of nitrogen. This three-way conversion only occurs when the
air/fuel ratio is near stoichiometry.

Three-Way Catalytic Converter:

The catalyst initiates and speeds up heat producing chemical reactions of the exhaust gas components so they are used up as much as possible. As the exhaust gases come in contact with the catalyst they are changed into mostly harmless products.

WARNING: EXHAUST GASES CONTAIN CARBON MONOXIDE WHICH CAN BE HARMFUL TO HEALTH AND ARE POTENTIALLY LETHAL. EXHAUST SYSTEM LEAKS SHOULD BE SERVICED IMMEDIATELY. NEVER OPERATE THE ENGINE IN ENCLOSED AREAS.

CAUTION: Leaded fuel must not be used in a vehicle fitted with a three way catalytic converter. The lead will damage the catalyst.