What is a catalytic converter?

Millions of people enjoy the many benefits provided by the motorcar. Few of us however are unaware of the effects of pollution on the atmosphere. One of the most effective anti-pollution automotive components (introduced in California in the 1970s) is the catalytic converter.

Catalytic converters are now compulsory on virtually all new cars sold in western Europe, the USA and most of the developed world, and have been found to dramatically reduce damaging exhaust emissions.

 ‘3 way’ catalytic converters are designed to remove the three most harmful exhaust emissions, ie;

• Carbon monoxide, a poisonous gas.
• Hydrocarbons, which cause ground level ozone.
• Nitrogen oxide, which contributes to smog and acid rain.

Typically, a catalytic converter consists of a stainless steel box, fitted to the exhaust system, which contains a ceramic or metal honeycombed monolith. The monolith is coated with precious metals such as platinum, rhodium and/or palladium to form the catalyst.

As the exhaust gases flow through the catalyst a chemical reaction converts the harmful emissions viz. carbon monoxide, hydrocarbons and nitrogen oxide, into nitrogen, carbon dioxide and water vapour.

These emissions are generally benign, (although carbon dioxide emissions are believed to contribute to global warming.)

The catalytic converter is of course part of an integrated emission control system.

It can only function efficiently at the specified operating temperature and the correct ratio of fuel/air entering the engine must be maintained. Unburnt fuel entering the catalyst (as a result of a misfire for example) can cause damage and unleaded fuel is essential as lead will poison the catalyst and render it ineffective.

It is important therefore that the engine management system on the car is maintained in in good working order order to prevent any loss of efficiency and prolong the life of the catalyst.