About a Catalytic Converter

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Catalytic converters are a vital part of any automotive emission system. These devices use heat to chemically react (catalyze) with harmful emissions like carbon monoxide, nitric oxides and unburnt hydrocarbons and convert them to more inert forms. They've been required on all cars sold in the united states since 1975, and have helped to change the landscape of the automotive industry worldwide.

History

  • Catalytic converters were first developed in the 1950s by Eugene Houdry, a French-American engineer. They first entered production for use on automobiles in 1973, and were legislated as mandatory in 1975. Other industries soon jumped on the green wagon, applying converters to practically anything with an engine, including forklifts, generators and battleships.

Function

  • All catalytic converters function on essentially the same principal. The converter housing contains a grid-like substrate that is designed to reach extremely high heat, finishing the combustion process begun by the engine and vaporizing contaminants. Many converters store excess oxygen from the catalytic process, using it to speed up the reaction under high-stress conditions. The inside of some converters can reach over 1,000 degrees under normal operation, and significantly more under meltdown conditions.

Types

  • Older converters used a lead pellet design to capture heat, forcing the exhaust to flow through and around the metal balls, which were trapped in a containing matrix. More modern converters use honeycomb-shaped matrices of platinum-palladium alloy, coated with a wash-coat of silica and alumina, which helps increase efficiency. The newest converters use a ceramic honeycomb which lasts longer, is more efficient and contains little or no precious and expensive platinum alloy.

Converter Drawbacks

  • Older catalytic converters were very heavy and restrictive, costing precious horsepower in the deficit days of the '70s and reducing fuel mileage by as much as 10 percent. The newest high-flow honeycomb designs, however, flow significantly better than lead-pellet types. Converters often produce harmful emissions of their own: hydrogen sulfide and ammonia are the most common, but some also produce the organic toxin dioxin.

Cash for Cats

  • Catalytic converter theft is rampant in some areas, since older units contain great quantities of the aforementioned precious metals. A typical catalytic converter contains over $200 worth of platinum, palladium and rhodium. But don't break out the reciprocating saw and retirement plan just yet; according to the EPA, the cost to extract these precious metals from used converters makes recycling them for the platinum only slightly more economical than simply refining more.

References

  • Photo Credit Image by Flickr.com, courtesy of Chris Keating
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