The catalyst is a device placed in the exhaust system of gasoline and diesel vehicles with the aim of converting the emitted pollutants into harmless for air exhaust. This conversion is accomplished by chemical reactions (eg oxidation and reduction) , occurring within the catalyst.
In these reactions :
- The carbon monoxide (CO) is oxidized to carbon dioxide (CO2).
- The unburned hydrocarbons (HC) are oxidized in water vapor (H2O).
- The Nitrogen oxides NOx are reduced to atmospheric nitrogen ( N2 ) .
The catalyst is an element in conditions of high temperature (above 250 C) helps out a reaction without the catalyst itself to take part in this. The placement of the catalyst is in the exhaust pipe near the exhaust manifold and before the muffler . There are ceramic and metal catalysts . Each category has specific advantages . Thus :
Metal :
- Longer Life
- Largest increase engine performance
- Resistant to shock
ceramic :
- Lower purchase cost
- Higher strength at temperatures above 1200 C
- Lower noise levels
Generally metal catalysts are considered more qualitative than ceramic . Automakers usually install ceramic catalysts . Few companies install metal catalysts , particularly in the top models. Those who wish to improve the exhaust system should install metal catalyst .