Catalytic Converters

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                                                                                                                            Aman Tuljapurkar

Catalytic Converters

A catalytic converter is a device used to reduce the toxicity of emissions from an . Catalytic converters are still most commonly used in   systems. Catalytic converters are also used on  sets, , mining equipment, , , , and other engine-equipped machines. A catalytic converter provides an environment for a  wherein toxic combustion by-products are converted to less-toxic substances.

Three-way catalytic converters

A three-way catalytic converter has three simultaneous tasks:

  1.  of  to  and : 2NOx → xO2 + N2 
  2.  of  to : 2CO + O2 → 2CO2 
  3. Oxidation of unburnt  (HC) to carbon dioxide and : 2CxHy + (2x+y/2)O2 → 2xCO2 + yH2O

Two-way catalytic converters

A two-way catalytic converter has two simultaneous tasks:

  1.  of  to : 2CO + O2 → 2CO2 
  2. Oxidation of unburnt hydrocarbons (unburnt and partially-burnt fuel) to carbon dioxide and : 2CxHy + (2x+y/2)O2 → 2xCO2 + yH2O
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Diesel engines

For compression ignition (i.e., ) engines, the most commonly used catalytic converter is the diesel oxidation catalyst. The catalyst uses excess O2 (oxygen) in the exhaust gas stream to oxidize CO (Carbon Monoxide) to CO2 (Carbon Dioxide) and HC (hydrocarbons) to H2O (water) and CO2. These converters often reach 90% effectiveness, virtually eliminating diesel odor and helping to reduce visible  (), however they are incapable of reducing NOx as chemical reactions always occur in the simplest possible way, and the existing O2 in the exhaust gas stream would react first.

To reduce NOx on a compression ignition engine it is necessary to change ...

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