Define: Catalytic Converter

A catalytic converter is a device used in the exhaust system of a vehicle to reduce the emissions of harmful pollutants, such as carbon monoxide, nitrogen oxides, and hydrocarbons. It works by catalysing a chemical reaction that converts these pollutants into less harmful substances. The use of catalytic converters is mandated by law in many jurisdictions to meet emissions standards and protect air quality. Theft or tampering with a catalytic converter is illegal and can result in criminal charges.

A catalytic converter is an emissions control device that transforms harmful gases and pollutants in exhaust emissions from internal combustion engines into less harmful substances through catalysing a redox reaction. These converters are primarily employed with gasoline or diesel-fueled internal combustion engines, including lean-burn engines, and are sometimes used with kerosene heaters and stoves.

The widespread adoption of catalytic converters began in the automotive industry of the United States. In order to meet stricter regulations on exhaust emissions set by the U.S. Environmental Protection Agency, most gasoline-powered vehicles manufactured from the 1975 model year onwards were equipped with catalytic converters. Initially, “two-way” converters were employed, which reacted oxygen with carbon monoxide (CO) and unburned hydrocarbons (HC) to produce carbon dioxide (CO2) and water (H2O). However, these two-way converters became outdated by 1981 when “three-way” converters were introduced, which also reduced oxides of nitrogen (NOx). Nevertheless, two-way converters are still used on lean-burn engines to oxidise particulate matter and hydrocarbon emissions, such as in diesel engines that typically use lean combustion, as three-way converters necessitate fuel-rich or stoichiometric combustion to effectively reduce NOx.

While catalytic converters are most commonly associated with automobile exhaust systems, they are also used in other applications, including electrical generators, forklifts, mining equipment, trucks, buses, locomotives, motorcycles, and ships. They are even integrated into certain wood stoves to control emissions. The implementation of catalytic converters in these diverse applications is often in response to government regulations, either related to environmental standards or health and safety regulations.

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This glossary post was last updated: 28th April 2024.