Catalytic converters convert noxious emissions of hydrocarbons (HC) and carbon monoxide (CO) into harmless carbon dioxide and water. The reaction takes place inside the reactor(s) at great heat using platinum or palladium metals as the catalyst. The 5 in. (127mm) diameter units are installed in the exhaust system ahead of the mufflers. They are designed, if the engine is properly tuned, to last 50,000 miles or more before replacement.
See Figure 1
There are different types of catalytic converters for your vehicle. The most common type used on vehicles today is the Three Way Catalytic Converter (TWC). This converter contains either platinum and rhodium to pallidadium and rhodium. The TWC converter catalyzes the oxidation reactions of the unburned hydrocarbons and carbon monoxide and the reduction reaction of oxides of nitrogen. The three way conversion only occurs with the air fuel/ratio near stoichiometry.
Lead-free gasoline must be used on all converter equipped vehicles.
A Catalytic converter should last you almost the lifetime of your vehicle if taken care of. You should never allow your engine run at an idle for long periods of time. This can overheat the converter and shorten the life.