Effects of Air Pollutants on Health

Introduction to Air Pollutants

• Combustion of fuels in cars leads to the release of harmful pollutants.
• Notable pollutants include:
  • Nitrogen Dioxide (NO2)
  • Carbon Monoxide (CO)

Role of Catalytic Converters

• Catalytic converters convert harmful substances into harmless gases.
• Definitions:
  • Catalyst: A substance that speeds up a chemical reaction without being consumed in the process.

Types of Catalysts in Catalytic Converters

1. Reduction Catalyst

   • First stage of the catalytic converter.
   • Converts nitrogen oxides (NO or NO2) into nitrogen (N2) and oxygen (O2).
   • Reaction occurs on the surface of the catalyst.
   • Equation:
     2 NO + 2 CO → N2 + 2 CO2

2. Oxidation Catalyst

   • Second stage of the catalytic converter.
   • Oxidizes unburned hydrocarbons and carbon monoxide.
   • Utilizes platinum and palladium catalysts.
   • Equation: CxHy + O2 → CO2 + H2O

Structure of Catalytic Converters

• Honeycomb Structure:
  • Maximizes surface area exposure of the catalyst to exhaust gases.
  • Minimizes the amount of metal catalyst required (which is expensive: platinum, rhodium, palladium).

Oxygen Sensor and Monitoring

• The catalytic converter includes an oxygen sensor to monitor exhaust oxygen levels.
• This sensor links to an automatic control system:
  • Adjusts the carburetor to modify the air-to-fuel ratio.
  • Ensures optimal conditions for oxidation, allowing complete burning of unburned hydrocarbons and carbon monoxide.

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