2 way Catalytic Converters

Unlike the three way catalytic converter, 2-way catalytic converters are used to reduce CO and HC gases. 2 way converters don’t eliminate or eliminate very little amount of NO_X. They are made of only oxidation catalysts (platinum (Pt) and palladium (Pd)).

It is made of honeycomb ceramic structure with a coating of alumina. A secondary coat of precious materials, platinum and palladium is applied to the structure.

The oxidation catalyst is honeycomb shaped structure made of platinum and palladium. Since, it is an oxidation reaction; the catalyst will try to attract the oxygen atoms. The CO bond is strong enough to be split by the catalyst. Thus CO molecule as a whole will be attracted towards the catalyst surface. The catalyst surface will also attract the oxygen molecules (O₂). Now, since O₂ molecules’ bonds are weaker than the CO bond, the O₂ is split into individual oxygen atoms (O). The oxygen atoms will bond with the CO molecules to form CO₂.

2CO + O₂ → 2CO₂

The hydrocarbon (HC) molecules also get treated by the oxidation catalyst. When HC molecules come in contact with the catalyst surface, they are split into hydrogen (H) and carbon (C). Both hydrogen and carbon bond with oxygen to form water vapor (H₂O) and carbon dioxide (CO₂).

C₈H₁₈ + 17O₂ → 8CO_{2 +} 18H₂O

 Or

CH₄ + 2O₂ → CO_{2 +} 2H₂O

Etc….

_{Related links:}

• Exhaust Gas Recirculation (EGR)

• Fuel Vapor Canister

• Emission norms in India

• BS 6 norms in India

• Catalytic Converter (3-way)