'Automobile Catalytic Converters'

• A catalytic converter is a device used to reduce the toxicity of emissions from an internal combustion engine
• Three-way catalytic converters: These have three simultaneous tasks;
  • Reduction of nitrogen oxides to nitrogen and oxygen
  • Oxidation of (non greenhouse gas, but toxic) carbon monoxide to less harmful (greenhouse gas) carbon dioxide
  • Oxidation of unburnt carcinogenic hydrocarbons (HC) to carbon dioxide and water
• Two-way catalytic converters: These have two simultaneous tasks;
  • Oxidation of (non greenhouse gas) carbon monoxide to harmless (greenhouse gas) carbon dioxide
  • Oxidation of unburnt hydrocarbons (unburnt and partially-burnt fuel) to carbon dioxide and water
• Catalyst poisoning and deactivation: Catalytic converters become ineffective in the presence of lead due to catalyst poisoning. Therefore, vehicles equipped with catalytic converters must only be run on unleaded gasoline
• The catalytic converter consists of several components: The core, or substrate; the washcoat; and the catalyst itself, which is most often a precious metal
• Rich Burn Spark Ignition Engines Catalytic converters are used on spark ignition (gasoline; liquified petroleum gas (LPG); flexible fuel vehicles burning varying blends of E85 and gasoline; compressed natural gas (CNG)) engines; and compression ignition (diesel) engines
• Regulations: Emissions regulations vary considerably from jurisdiction to jurisdiction, as do what engines are regulated.
• Regulatory agencies: The agencies charged with regulating engine emissions vary from jurisdiction to jurisdiction, even in the same country
• Criticisms of catalytic converters: Catalytic converters have proven to be reliable devices and have been successful in reducing noxious tailpipe emissions. However, they may have some adverse environmental impacts in use: The requirement for a rich burn engine to run at the stoichiometric point means it uses more fuel than a "lean burn" engine running at a mixture of 20:1 or less. This increases the amount of fossil fuel consumed and the carbon dioxide emissions of the vehicle

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