††††A catalyst is a chemical substance that speeds up a chemical change. The catalyst itself is not changed. Catalysts are widely used in industrial chemistry. Enzymes are also catalysts.
A catalytic converter is a device for reducing the amounts of poisonous pollutants in the exhaust gases from internal combustion engines. The exhaust gases are passed over a mixture of catalysts which turn most of the poisonous hydrocarbons into carbon dioxide and water. This reduces some forms of pollution, but the carbon dioxide produced can contribute to the greenhouse effect.
