Catalytic converter: The aftertreatment of the exhaust gases

The catalytic converter is used for post-processing the harmful exhaust gases in vehicles with internal combustion engine. These gases are converted into carbon dioxide and water by a chemical process of oxidation or reduction.

Three-way catalytic converters (TWC)

The naming of the three-way catalytic converter is derived from the fact that three pollutants are converted by it.

  • unburned hydrocarbons (HC) in carbon dioxide (CO2) and water vapor (H2O)
  • Carbon monoxide (CO) in carbon dioxide (CO2)
  • Nitrogen oxides (NOX) in nitrogen (N2) and oxygen (O2)

A lambda control ensures a high degree of conversion of the pollutants. The catalyst itself changes temporarily during the reaction, and then returns to its initial state.



The 1956 patented device of the French engineer Eugene Houdry, which was fitted to the exhaust, was the time of the exhaust gas catalyst.

After the use in gasoline engines, diesel engines were equipped with catalytic converters in the late 1980s.

Modern catalytic converters achieve the required operating temperature of about 500 degrees faster after a cold start, and are more resistant to vibration.

Catalytic converter

Volkswagen and Ford, Fiat, Peugeot and almost all Japanese continue to sell cars that pollute the air with their exhaust fumes more than necessary. For the time being, these car companies are not making the regulated catalytic converter a standard feature, and they remain quite consistent with this: environmental protection only takes place when the state enforces it.

– German magazine: Der Spiegel 24.07.1889