Figure 1: Catalytic converter in vehicle exhaust system
A catalytic converter (also known as a 'cat') has been a common feature of vehicle exhaust systems since around the 1990s.
It is an emissions control device that reduces the harmful level of exhaust gases produced by internal combustion before they enter the atmosphere.
It works by converting the harmful exhaust gases into less harmful ones as the gases pass through it. These harmful gases can include a number of pollutants, such as nitrogen oxides, carbon monoxide, and hydrocarbons.
Housed inside a stainless steel can lies a ceramic monolith. This is made of a honeycomb structure which allows free air flow and maximum surface area.
Figure 2: Ceramic honeycomb structure inside the converter
This is coated with a combination of up to three precious metals: platinum, palladium, and rhodium.
This precious metal coating enables the conversion of exhaust gases that pass through the honeycomb monolith.
The monolith is held in place by a matting which initially expands when exposed to heat. This supplies the pressure needed to keep the monolith secure.
As a byproduct of internal combustion, exhaust gases including the pollutants mentioned previously enter the cat.
These gases then pass through the monolith. As they do so, a chemical reaction takes place as a result of the precious metal coating which acts as a catalyst.
This reaction takes place once the cat is at operating temperature at around 300 degrees Celsius.
Less harmful exhaust gases containing carbon dioxide, nitrogen, and water then exit the cat before eventually being expelled from the exhaust tailpipe.
Figure 3: Chemical conversion process in catalytic converter
The catalytic converter plays a crucial role in reducing harmful emissions by converting toxic gases like carbon monoxide, nitrogen oxides, and hydrocarbons into less harmful substances such as carbon dioxide, nitrogen, and water vapor.
Using precious metals like platinum, palladium, and rhodium as catalysts, it helps vehicles meet environmental regulations while improving air quality.
Regular maintenance and recognizing early signs of failure can extend its lifespan and keep your engine running efficiently.
