Catalytic Converter Fact Sheet
Background Information:
 First made in 1975 by John J. Mooney and Dr. Carl D. Keith. It was dedicated to stop air pollution
 A device used to reduce the toxicity of emissions from an internal combustion engine
 Works by using a specific catalyst to inspire a chemical reaction
 Convert toxic by-products from engines into less toxic substances
 In order to control emissions, amount of fuel used is carefully controlled
 Air-to-fuel ratio close to the stoichiometric point
 Ideal ratio of air to fuel. At this ratio, all of the fuel will be burned using all the oxygen in the air.
 For gasoline, ratio = 14.7 : 1. Meaning each mole of gasoline, 14.7 moles of air will be combusted
 Not constant, can easily be changed
 Preheating can increase efficiency
 Catalytic Converters in Diesel engines aren’t as efficient. Diesel engines are cooler run cooler engines.
 Even though it take away the toxins, but a major producer of CO2
 Scientists are trying to find a way to conquer both problems without any compromises
How it Works:
 The main emissions of a car are: N2(g), CO2(g) and H2O(g)
 Not considered to be health hazards, but CO2 contributes to global warming
 Since combustions are never perfect, smaller amounts of more harmful toxins are released. The catalytic
converter is made to reduce them
 CO: poisonous gas that is colourless and odourless
 Hydrocarbons: smog, evaporated unburned fuel, harmful
 NO & NO2: contributor to smog and acid rain
 2 different kinds of catalysts are needed. Reduction catalyst and oxidation catalyst
 Consist of ceramic structure coated with a metal catalyst. Usually platinum, rhodium and/or palladium.
Gold may also be used. Cheaper than those materials and reduce 40% more toxins
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 Expose maximum surface area of catalyst to the exhaust stream while minimizing catalyst required
Modern cars have three-way catalytic converters. 3 regulated commissions.
First stage, reduction catalyst. Uses Pt & Rb to reduce NO & NO2
 NO  N2 + O2 2NO2  N2 + 2O2
 When NO or NO2 contacts the catalyst, catalyst rips N atoms out of molecule, freeing the O2. The N then
bond with other N to for N2
Second stage, oxidation catalyst. Uses Pt & Pd to reduce hydrocarbons and CO
 2CO + O2  2CO2
 CxH2x+2 + [(3x+1)/2]O2 → xCO2 + (x+1)H2O
 Reduces unburned hydrocarbons and CO by burning them over a catalyst
Third stage, control system. Monitors the exhaust stream, control fuel injection system.
 A sensor will tell the engine computer how much oxygen is in the exhaust. Oxygen can be increased or
decreased by adjusting the air-to-fuel ratio. It makes sure that the engine is running close to
stoichiometric point, and it also make sure there are sufficient oxygen to combust the hydrocarbon and
CO
Bibliography
Who Invented the Catalytic Converter? | eHow.com. (n.d.). eHow | How To Do Just About Everything! | How
To Videos & Articles. Retrieved November 29, 2010, from
http://www.ehow.com/facts_5901250_invented-catalytic-converter_.html
Nice, K. (n.d.). HowStuffWorks "Car Engine Emissions". Howstuffworks "Auto ". Retrieved November 29,
2010, from http://auto.howstuffworks.com/catalytic-converter1.htm
Catalytic converter - Wikipedia, the free encyclopedia. (n.d.). Wikipedia, the free encyclopedia. Retrieved
November 30, 2010, from http://en.wikipedia.org/wiki/Catalytic_converter
Anglin, D. L. (2010). Catalytic Converter. Grolier Multimedia Encyclopedia. Retrieved November 30, 2010,
from Grolier Online http://gme.grolier.com/article?assetid=0054700-0