CATALYTIC CONVERTER

WHAT IS CATALYTIC CONVERTER?

Catalytic converter is the device that converts the environmentally harmful substances into less harmful substances.

Catalytic converter is widely used in automobiles. A catalytic converter provides a second burning stage to hydrocarbons that are not burnt completely and performs a reduction process on the polluting gases. This burning and reduction is made by the help of several catalyzers (platinum, palladium or rhodium). The second burning stage is completed outside the engine, so there is no utilizable energy gained from this process.

Chemical Reactions

3 following reactions occur simultaneously in a 3 way catalytic converter:

  1. Burning carbon monoxide and converting it to carbon dioxide: 2CO + O2 → 2CO2
  2. Reduction of nitrogen oxides to nitrogen: NO2 → O2 + N2
  3. Burning unburned hydrocarbons (unburned fuel) and converting into carbon dioxide and water: CxHy + nO2 → xCO2 + mH2O
Metal core converter cutaway
Metal core converter cutaway

In means of balanced working, these three reactions are not in balance both in rich mixture or lean mixture. While first two reactions occur more often than the third in lean mixture, the third reaction occurs more in rich mixture. So the fuel that is not completely burned because of the rich mixture is burned in the catalytic converter. Catalytic converter channels are coated with Platinum, Palladium, Rhodium and Cerium. The Palladium and Platinum inside the converter provides the oxidation of HC and CO and the Rhodium provides the reduction of NOx. Cerium stores and keeps the needed level of oxygen varying during the rich or lean operating of the engine.