A catalytic converter is a device used to reduce the
toxicity of emissions from an internal combustion
Catalytic converters are most commonly used in
motor vehicle exhaust systems.
Catalytic converters are also used on generator sets,
mining equipment, trucks, buses, trains, and other
A catalytic converter provides an environment for a
chemical reaction wherein toxic combustion by-
products are converted to less-toxic substances.
The catalytic converter was first invented by
Eugene Houdry in the 1950’s.
Tetra-ethyl lead present in gasoline "poisoned"
the converter by forming a coating on the
catalyst's surface, effectively disabling it.
The catalytic converter was further developed
by John J. Mooney and Carl D. Keith at the
Engelhard Corporation, creating the first
production catalytic converter in 1973.
The core is often a ceramic honeycomb in
modern catalytic converters, but stainless steel
foil honeycombs are used, too.
The honey-comb surface increases the amount
of surface area available to support the
catalyst, and therefore is often called a
A washcoat is used to make converters more
efficient, often as a mixture of silica and
The catalyst is added to the washcoat (in
suspension) before being applied to the core.
Platinum is the most active catalyst and is widely
Palladium and rhodium are two other precious
Platinum and rhodium are used as a reduction
Platinum and palladium are used as an
Cerium, iron, manganese and nickel are also
1. Two way Catalytic Converter
Oxidation of carbon monoxide to carbon
dioxide: 2CO + O2 → 2CO2
Oxidation of unburnt hydrocarbons (unburnt
and partially-burnt fuel) to carbon dioxide and
2. Three way Catalytic converter
Reduction of nitrogen oxides to nitrogen and
oxygen and same reactions as in two way
Catalyst poisoning occurs when the catalytic converter is
exposed to exhaust containing substances that coat the
working surfaces, encapsulating the catalyst so that it
cannot contact and treat the exhaust.
The most notable contaminant is lead.
Any condition that causes abnormally high levels of
unburned hydrocarbons — raw or partially-burnt fuel — to
reach the converter will tend to significantly elevate its
temperature, bringing the risk of a meltdown of the
substrate and resultant catalytic deactivation and severe
exhaust restriction .
Reduces fuel economy of cars resulting in a
greater use of fossil fuels.
Although catalytic converters are effective at
removing hydrocarbons and other harmful
emissions, most of exhaust gas leaving the
engine through a catalytic converter is carbon
dioxide (CO2), which is responsible for the
green house effect.
Some early converter designs created a great
deal of restriction to the flow of exhaust,
which negatively affected vehicle
performance, drivability, and fuel economy.
It had been stated that catalytic converters are
known in a lot of cases to have an excessively
long warm-up time period, in a great deal of
cases ranging up to thirty-minutes.