What is a three way catalytic converter give the catalyst used in it?

 A three-way catalytic converter is an essential component used in automobile exhaust systems to reduce harmful emissions produced by internal combustion engines. It helps in converting harmful gases such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOₓ) into less harmful substances before they are released into the atmosphere.

The Three Functions of a Three-Way Catalytic Converter:

1. Oxidation of Carbon Monoxide (CO):

   • CO is converted into carbon dioxide (CO₂).
   $$2CO + O₂ \rightarrow 2CO₂$$

2. Oxidation of Hydrocarbons (HC):

   • Hydrocarbons are burned to produce carbon dioxide (CO₂) and water (H₂O).
   $$C₈H₁₈ + 25O₂ \rightarrow 16CO₂ + 18H₂O$$

3. Reduction of Nitrogen Oxides (NOₓ):

   • NOₓ are reduced to nitrogen (N₂) and oxygen (O₂).
   $$2NO \rightarrow N₂ + O₂$$

Catalysts Used in a Three-Way Catalytic Converter:

The catalyst in a three-way catalytic converter is typically made of a combination of precious metals that promote the chemical reactions without being consumed in the process. The most common catalysts used include:

1. Platinum (Pt):

   • Platinum is primarily responsible for facilitating the oxidation reactions, particularly the oxidation of carbon monoxide and hydrocarbons.

2. Palladium (Pd):

   • Palladium also plays a role in the oxidation of hydrocarbons and carbon monoxide.

3. Rhodium (Rh):

   • Rhodium is crucial for the reduction of nitrogen oxides (NOₓ) to nitrogen and oxygen.

Working Mechanism:

• The exhaust gases from the engine pass through a ceramic or metallic substrate inside the converter, which is coated with a layer of these precious metals (platinum, palladium, and rhodium).
• As the gases flow over the catalyst, the metals facilitate chemical reactions, converting harmful substances into less harmful ones (CO₂, H₂O, and N₂).

Summary:

A three-way catalytic converter is designed to reduce three primary pollutants in exhaust gases: carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOₓ). The catalysts used in this process are typically platinum (Pt), palladium (Pd), and rhodium (Rh).

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