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- Catalytic converters are designed to clean up the exhaust fumes from petrol-driven vehicles, which are otherwise the major threat to air quality standards in congested urban streets and on motorways. Converters remove carbon monoxide, the unburned hydrocarbons and the oxides of nitrogen. These compounds are damaging to human health and the environment in a variety of ways. The converter is attached to the vehicle' s exhaust near the engine. Exhaust gases pass through the cellular ceramic substrate, a honeycomb-like filter. While compact, the intricate honeycomb structure provides a surface area of 23.000 square metres. This is coated with a thin layer of platinum, palladium and rhodium metals, which act as catalysts that simulate a reaction to changes in the chemical composition of the gases. Platinum and palladium convert hydrocarbons and carbon monoxide into carbon dioxide and water vapour. Rhodium changes nitrogen oxides and hydrocarbons into nitrogen and water, which are harmless.
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| Abstract from DBPedia | A catalytic converter is an exhaust emission control device that converts toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction. Catalytic converters are usually used with internal combustion engines fueled by gasoline or diesel, including lean-burn engines, and sometimes on kerosene heaters and stoves. The first widespread introduction of catalytic converters was in the United States automobile market. To comply with the U.S. Environmental Protection Agency's stricter regulation of exhaust emissions, most gasoline-powered vehicles starting with the 1975 model year are equipped with catalytic converters. These "two-way" converters combine oxygen with carbon monoxide (CO) and unburned hydrocarbons (HC) to produce carbon dioxide (CO2) and water (H2O). Although two-way converters on gasoline engines were rendered obsolete in 1981 by "three-way" converters that also reduce oxides of nitrogen (NOx); they are still used on lean-burn engines to oxidize particulate matter and hydrocarbon emissions (including Diesel engines, which typically use lean combustion), as three-way-converters require fuel-rich or stoichiometric combustion to successfully reduce NOx. Although catalytic converters are most commonly applied to exhaust systems in automobiles, they are also used on electrical generators, forklifts, mining equipment, trucks, buses, locomotives, motorcycles, and on ships. They are even used on some wood stoves to control emissions. This is usually in response to government regulation, either through environmental regulation or through health and safety regulations.三元触媒（さんげんしょくばい、英: Three-Way Catalyst, TWC）は、ガソリン車・ディーゼル車の排出ガス中の3種類の有害成分を酸化・還元によって同時に浄化する装置である。 (Source: http://dbpedia.org/resource/Catalytic_converter) |
