Autocatalyst - PMM

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What is an Autocatalyst?

Production Autocatalyst.jpg

An autocatalyst is a cylinder of circular or elliptical cross section made from ceramic or metal formed into a fine honeycomb and coated with a solution of chemicals and platinum group metals. It is mounted inside a stainless steel canister (the whole assembly is called a catalytic converter) and is installed in the exhaust line of the vehicle between the engine and the silencer (muffler).

How do autocatalysts help the environment?

Vehicle exhaust contains a number of harmful elements which can be controlled by the platinum group metals in autocatalysts. The major exhaust pollutants are:

  • carbon monoxide, which is a poisonous gas
  • oxides of nitrogen, which contribute to acid rain, low level ozone and smog formation and which exacerbate breathing problems
  • hydrocarbons, which are involved in the formation of smog and have an unpleasant smell
  • particulate, which contains known cancer-causing compounds

Autocatalysts convert over 90 per cent of hydrocarbons, carbon monoxide and oxides of nitrogen from gasoline engines into less harmful carbon dioxide, nitrogen and water vapour. Autocatalysts also reduce the pollutants in diesel exhaust by converting over 90 per cent of hydrocarbons, carbon monoxide and particulate matter into carbon dioxide and water vapour.

A brief history of pollution controls

In 1975 the United States, following the lead of the Californian Air Resources Board, and Japan applied clean air legislation which led to autocatalysts being fitted to light duty vehicles. Many other countries with large vehicle markets have followed since then, including South Korea (1987), Mexico (1989), the member states of the European Union (1993), Brazil (1994), Russia (1999) and China and India (2000). Today, over 95 per cent of all new vehicles sold globally each year are fitted with catalytic converters.

Autocatalysts in the future

As the number of cars on the road increases, further cuts in pollution per vehicle are needed to keep improving air quality. Many governments, including those of the USA, Japan and the EU continue to apply increasingly stricter emissions standards. Advanced autocatalysts for gasoline and diesel cars and heavy trucks are being developed by Johnson Matthey in partnership with the world automotive industry to meet the new rules. In many cases these will lead to greater use of the catalyst metals platinum, palladium and rhodium.

Autocatalyst demand for platinum, palladium and rhodium is estimated in our market data tables.


’Twenty-Five Years of Autocatalysts’

The first autocatalysts were manufactured on a commercial scale by Johnson Matthey at Royston, UK. This article looks at the background to this major contribution towards cleaning urban air and briefly...

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