Catalytic Converters

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Catalytic Converters
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Catalytic Converters

• Catalytic converters are heterogeneous catalysts
• Function
• Oxidizes CO and unburned hydrocarbons to CO2 and
  H2O
• Reduction of NO to N2
• SMOG CO and NO

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Design of a Converter

• Must be able to function over a wide range of
  temperatures
• Must continue to be active despite the additives
  in gasoline
• Must be rugged in design

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CO and NO Conversion

• Use metal oxides (CuO and Cr2O3) and noble metals
  such as platinum
• These are supported in either a bead or honeycomb
  structure made from alumina, Al2O3
• Adsorbs O2 gas from exhaust, weaken O2 bond and
  allows them to react with CO to form CO2

Ceramic
Steel
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Benefits

• Great heterogeneous catalysts
• Gases are only in contact with catalyst for 100
  to 400 ms, but
• 96 of hydrocarbons and CO are converted to CO2
  and H2O
• NO emission is cut to 76
• Use expensive metals (more than gold) platinum
  and rhodium which have been stolen by thieves and
  sold for !