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What we want to do is reduce the pollution from vehicle exhaust to give us cleaner air.

You probably already know what gases are formed in internal combustion engines.

The Introduction of Catalytic Converters
image: vehicle exhaust


Can you name them?

What harm do they cause?

button: providing answer to question

To reduce air pollution catalytic converters have been fitted to cars since the 1970s.

What is a catalytic converter?

It is a stainless steel box mounted in the exhaust system. Inside is a catalyst on a ceramic or metallic support protected from vibration and shock by a resilient ceramic or metallic 'mat'. The catalysts are combinations of platinum, palladium and rhodium.

imae: three-way closed loop catalytic converter
images: catalysis in a strong protective mat inside a strong steel catalytic converter
Three-way catalysts operate in a closed-loop system including an oxygen sensor to regulate the air/fuel ratio in petrol engines. The catalyst can then simultaneously oxidise carbon monoxide and hydrocarbons to carbon dioxide and water while reducing NOx to nitrogen. The push for development came from legislation.
By 2001 275 million of the world's 500 million cars were fitted with catalysts

85% of all new cars worldwide are fitted with catalytic converters.

How bad was it?

Between 1970 and 1989

  • CO emissions from vehicles in the United Kingdom increased by 74 per cent
  • NOx emissions more than doubled.

By 1993, road vehicles were the source of

  • 90 per cent of all emissions of CO
  • 49 per cent of all emissions of NOx.
1974 Cars with catalytic converters introduced in USA
1974 first with thermal catalysts
1975 then oxidation catalysts
1980 then with three way catalyst
1985 Introduced in Europe
1993 Legislation passed requiring catalytic converters in Europe

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