BY
BY
THOMAS C
THOMAS CHERIAN A1HERIAN A11MAE171MAE17
DINESH
DINESH TEJ A1TEJ A11MAE181MAE18
VITU - ARAI
CONTENTS
CONTENTS
Introduction & History of Catcon
Introduction & History of Catcon
Construction of Catcon & Location
Construction of Catcon & Location
Types Of Catcon
Types Of Catcon
Damage to Catcons
Damage to Catcons
Negative aspects of Catcon
Negative aspects of Catcon
Conclusion
Conclusion
WHAT IS A CATALYTIC
CONVERTER (CATCON)
A
catalytic converter
is a vehicle
emissions
control
device
which
converts
toxic
by
products
of combustion in the exhaust of
an internal combustion engine to less
toxic
substances
by
way
of
catalysed chemical reactions.
BRIEF HISTORY OF THE CATALYTIC CONVERTER
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 bu John J. Mooney and Carl D. Keith at the Engelhard Corporation,
creating the first production of catalytic converter in 1973.
USES OF A CATCON
Used to reduce toxicity of emissions
from an IC engine.
Mostly used in motor vehicle exhaust
system.
Catcons are also used in gensets,
forklift, mining equipments, trucks,
buses, trains and other
COMPONENTS OF
CATCON
4 Components
Mat
Ceramic substrate
Can
Catalyst
CONSTRUCTION OF
CATCON
Metal core converter & Ceramic core
converter.
The core is often a ceramic
honeycomb(codierite 2 MgO • 2AI2O3 • 5SiO2) in modern catalytic converters, but
stainless steel foil honeycombs are also used.
Metallic cores are less expensive to build in
small production runs, and are used in sportscars where low back pressure and reliability under continuous high load is required.
The honeycomb surface increases the amount
of surface area available to support the
A washcoat( Aluminum oxide, titanium
dioxide, silicon dioxide, or a mixture
of silica and alumina can be used) is used to make the converter more efficient, often as a mixture of silica & alumina.
The washcoat when added to the core,
forms a rough, irregular surface, which has a far greater surface area than the flat core surfaces do, which then gives the converter core a larger surface area, and therefore
more places for active precious metal sites.
The catalyst is added to the washcoat
before being applied to the core.
Pt is the most active catalyst and is most
widely used.
Pt & Rh are used as reduction catalysts.
Pt & Pd are used as oxidaton catalysts.
Cerium, Fe, Mn & Ni are also used.
CATCON LIGHT OFF
TEMPERATURE
Light off temperature of a catalytic
converter is the temperature at which
the catalytic converter become 50%
effective.
Typical light off temperature is
TYPES OF CATCON
2 way catcon
2 WAY CATALYTIC
CONVERTER
Used in diesel engines
Has two simultaneous tasks
1.
Oxidation of CO to CO2
2.
Oxidation of unburned hydrocarbons to C02 &
water.
3 WAY CATALYTIC
CONVERTER
Used in SI engines.
There is control of Nox, CO & HC emissions.
1.
Reduction of nitrogen oxides to nitrogen and
oxygen.
2.
Oxidation of CO to CO2.
3.
Oxidation of unburned hydrocarbons to C02
These three reactions occur most
efficiently when the catalytic converter receives exhaust from an engine running slightly above the stoichiometric point. This is between 14.6 and 14.8 parts air to 1 part fuel, by weight, for gasoline.
When lean, the system is in oxidizing
condition. In that case, the converter's two oxidizing reactions are favoured, at the
During rich condition reduction of NOx is
favoured, at the expense of CO and HC oxidation.
Three-way catalytic converters can store
oxygen from the exhaust gas stream ( using Cerium), usually when the air fuel
ratio goes lean. When insufficient oxygen is available from the exhaust stream the
stored oxygen is released and consumed. This happens either when oxygen derived from Nox reduction is unavailable or certain maneuvers such as hard acceleration
enrich the mixture beyond the ability of the converter to compensate.
EQUATIONS FOR REACTIONS IN A
CATCON
CO + NO
CO2 + N2
DAMAGE TO CATCONS
Catalytic poisoning occurs when the
catalytic converter is exposed to exhaust containing substances that coat the
working surfaces, thus encapsulating the catalyst so that it cannot contact and treat the exhaust.
The most notable contaminant is lead. Other common catalyst poisons include
fuel sulphur, manganese, silicone, and phosphorous.
Any condition that causes abnormally
high levels of unburned hydrocarbons
(raw or partially burned fuels) 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
NEGATIVE ASPECTS OF
CATCON
Some early converter designs created a
great deal of restriction to the flow of
exhaust, which negatively affected vehicle performance, drivability and fuel economy.
Has a long warm-up time period. The
catalyst light off temperature is 250 – 300 degree celsius. Vehicles emit most of their pollution during the first five minutes of
engine operation before the catalytic
converter has warmed up sufficiently to be effective.
Reduces fuel economy of cars resulting
in a greater use of fossil fuels.
Although catcon reduces the
hydrocarbons & other harmful
emissions, most of the exhaust gases
leaving the engine through the catcon is
CO2, which is responsible for
greenhouse effect.
Pt, Pd & Rh are precious metals and
CONCLUSION
Catalytic converter is a very effective
device to reduce the emissions from IC
engines.
REFERENCES
[1]Heck, R. M., Farrauto, R. J. and Gulati, S. T., Catalytic Air Pollution Control: Commercial Technology, 2nd Ed. John Wiley & Sons, New York; 2002
[2] Gulati, S. T., Ceramic Catalyst Supports for Gasoline Fuel, Chap.2 in Structured Catalysts and Reactors, 2nd Ed. Taylor & Francis Group, Boca Raton, FL; 2006
[3] Catalytic Converters. International Platinum Group Metals Association. Retrieved January 10, 2011.
[4] http://en.wikipedia.org/wiki/Catalytic_converter [5]
