Kiera Jefferson
Cars, buses, and trucks have been a great gift to the world, but their engine pollution spoils the places where we live and harms our health. Fortunately, most vehicles are now fitted with pollution-reducing units called catalytic converters, which turn the harmful chemicals in vehicle exhaust into harmless gases such as steam. Catalytic converters are simple devices that use basic redox reactions to reduce the pollutants a car makes. They are usually used with internal combustion engines fueled by gasoline or diesel. The first widespread introduction of catalytic converters was in the United States automobile market in 1975.
| Characteristics | Values |
|---|---|
| Purpose | To reduce harmful emissions from internal combustion engines |
| Function | Converts harmful pollutants into less harmful emissions |
| Effectiveness | Removes up to 98% of pollutants |
| Types | Two-way, three-way, diesel oxidation catalyst (DOC) |
| Composition | Metal housing, ceramic honeycomb-like interior, precious metals (platinum, rhodium, palladium) |
| Shortcomings | High cost, inefficient at low temperatures, increased fuel consumption |
| Applications | Cars, power plants, indoor air purification |
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What You'll Learn
- Catalytic converters turn harmful exhaust gases into less harmful emissions
- They are most effective at high temperatures, after the engine has warmed up
- They are made of precious metals like platinum, rhodium and palladium
- They are simple devices that use basic redox reactions to reduce pollutants
- They are usually fitted to the underside of cars, between the engine and tailpipe
Catalytic converters turn harmful exhaust gases into less harmful emissions
The combustion of fossil fuels releases a noxious mix of chemicals, including poisonous carbon monoxide gas, volatile organic compounds (VOCs) like formaldehyde, and nitrogen oxides, which react with VOCs to create ozone. This toxic mix of gases is released into the air through exhaust systems. Catalytic converters are devices that help reduce these harmful exhaust emissions. They are usually bolted to the underside of a car, with one pipe connected to the engine and the other to the tailpipe (exhaust).
The catalytic converter treats the exhaust before it leaves the car, removing a significant amount of pollution. It does this by using chemical catalysts to convert harmful pollutants into less harmful emissions. The hot, polluted fumes from the engine's cylinders blow over the catalyst, and chemical reactions take place on its surface. These reactions break apart the pollutant gases and convert them into safer gases that can be released into the air.
There are typically two different catalysts in a catalytic converter. The first catalyst tackles nitrogen oxide pollution through a chemical process called reduction, which removes oxygen. This process breaks up nitrogen oxides into nitrogen and oxygen gases, which are harmless as they already exist in the air around us. The second catalyst works through oxidation, which adds oxygen, and turns carbon monoxide into carbon dioxide. Another oxidation reaction turns unburned hydrocarbons in the exhaust into carbon dioxide and water.
Catalytic converters are simple yet effective devices, removing up to 98% of pollutants from exhaust gases. They are usually used with internal combustion engines fuelled by gasoline or diesel. However, they also have some shortcomings. For example, they only work at high temperatures, so when a car is started cold, the catalytic converter does little to reduce pollution. They are also expensive to produce due to the precious metals required, such as platinum, palladium, and rhodium.
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They are most effective at high temperatures, after the engine has warmed up
Catalytic converters are a simple yet important device in a car's emissions control system. They are designed to reduce immediate, local air pollution, and they do this by converting harmful pollutants into less harmful emissions before they leave the car's exhaust system. They are a large metal box, bolted to the underside of a car, with two pipes coming out of them. One of them (the input) is connected to the engine and brings in hot, polluted fumes from the engine's cylinders. The second pipe (the output) is connected to the tailpipe (exhaust).
The converters use chemical reactions to break apart the pollutant gases and convert them into other gases that are safe to blow out into the air. They are most effective at high temperatures (over 300°C/600°F), after the engine has warmed up. When you start your car when it is cold, the catalytic converter does little to reduce the pollution in your exhaust. This is because catalytic converters only work within a specific temperature range. This is one of their biggest shortcomings.
To solve this problem, some carmakers have moved the catalytic converter closer to the engine so that hotter exhaust gases reach the converter, and it heats up faster. However, this may reduce the life of the converter by exposing it to extremely high temperatures. Another solution is to preheat the catalytic converter, which can be done using electric resistance heaters.
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They are made of precious metals like platinum, rhodium and palladium
Catalytic converters are metal boxes bolted to the underside of vehicles, designed to reduce harmful emissions produced by internal combustion engines. They are indispensable components of modern vehicles, playing a critical role in reducing vehicle emissions and helping to improve air quality in cities worldwide.
The high cost of catalytic converters is due in part to the precious metals they contain, such as platinum, rhodium, and palladium. These metals are thinly coated onto a substrate, typically made of ceramic or metal, which is structured to maximise its surface area. The substrate is contained within a protective shell made of stainless steel, which is designed to withstand high temperatures and protect the inner components.
Platinum and palladium are primarily used to convert carbon monoxide and hydrocarbons into carbon dioxide and water. Rhodium is particularly effective at converting nitrogen oxides into nitrogen and oxygen. These metals are crucial to the functioning of catalytic converters, acting as catalysts that facilitate chemical reactions to convert harmful pollutants into safer compounds.
The use of these precious metals in catalytic converters has led to an increasing demand and, as a result, they have become a target for thieves. Recycling of catalytic converters is, therefore, important for both economic and environmental reasons.
The application of these metals onto the substrate is preceded by a washcoat, which serves to disperse the catalyst materials evenly, increasing the surface area available for the catalytic reaction and enhancing the efficiency of the conversion process.
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They are simple devices that use basic redox reactions to reduce pollutants
Catalytic converters are simple devices that use basic redox reactions to reduce pollutants. They are large metal boxes bolted to the underside of a car, with two pipes coming out of them. One of these pipes, the converter's "input", is connected to the engine and brings in hot, polluted fumes from the engine's cylinders. The second pipe, the converter's "output", is connected to the tailpipe (exhaust).
The catalytic converter treats the exhaust before it leaves the car and removes a lot of the pollution. As the gases from the engine fumes blow over the catalyst, chemical reactions take place on its surface, breaking apart the pollutant gases and converting them into other gases that are safe enough to blow out into the air. These gases are typically carbon dioxide, water vapour, and nitrogen gas.
Catalytic converters are mainly designed to reduce immediate, local air pollution. They can remove up to 98% of pollutants from exhaust fumes, and regulations requiring their installation have helped dramatically improve air quality in cities around the world since the 1970s. Despite their success, the dramatic increase in the number of vehicles on the planet over the last 50 years has caused an overall decline in air quality.
Catalytic converters have some shortcomings. They are inefficient before the car 'warms up', and they only work at a fairly high temperature (over 300°C/600°F). They also consume more fuel than a lean-burn engine, resulting in approximately 10% more CO2 emissions from the vehicle.
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They are usually fitted to the underside of cars, between the engine and tailpipe
A catalytic converter is a large metal box, bolted to the underside of a car, with two pipes coming out of it. One of these pipes, the converter's "input", is connected to the engine and brings in hot, polluted fumes from the engine's cylinders. The second pipe, the converter's "output", is connected to the tailpipe (exhaust).
The catalytic converter treats the exhaust before it leaves the car, removing a lot of the pollution. It uses chemical reactions to break apart the pollutant gases and convert them into other gases that are safe enough to blow out into the air. These chemical reactions are called oxidation and reduction. Oxidation involves adding oxygen, turning carbon monoxide into carbon dioxide, and unburned hydrocarbons in the exhaust into carbon dioxide and water. Reduction, on the other hand, involves removing oxygen, breaking up nitrogen oxides into nitrogen and oxygen gases.
Catalytic converters are usually fitted to the underside of cars, between the engine and tailpipe, to reduce harmful emissions before they leave the car's exhaust system. They are designed to reduce immediate, local air pollution, and they can remove up to 98% of pollutants from exhaust fumes.
However, catalytic converters also have some drawbacks. They are ineffective until the engine has warmed up, and they only work at high temperatures. They also require rare and expensive precious metals like platinum, palladium, and rhodium, which has led to an increase in thefts of catalytic converters.
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Frequently asked questions
A catalytic converter is a device that reduces harmful emissions from an internal combustion engine.
A catalytic converter uses chemical reactions to break apart and convert harmful pollutants into less harmful gases.
Catalytic converters reduce nitrogen oxide, carbon monoxide, hydrocarbons, and particulate matter emissions.
Catalytic converters only work at high temperatures, are expensive due to the precious metals used in their construction, and can be targets for thieves.
While catalytic converters are widely used, alternatives such as selective catalytic reduction (SCR) and NOx adsorbers have been developed for lean-burn engines.
