The document discusses catalytic converters, which are vehicle emission control devices that convert toxic pollutants in exhaust gas into less toxic pollutants through catalyzed redox reactions. It describes the construction of catalytic converters including the ceramic monolith core, wash coat, and precious metal catalysts. The document explains how catalytic converters work to reduce oxides of nitrogen, carbon monoxide, and unburnt hydrocarbons in exhaust. It also covers the types of catalytic converters, their use in diesel engines, proper installation, potential damage from contaminants, and their role in reducing toxic emissions despite some adverse environmental impacts.

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KARNATAKA LAW SOCIETY’S
GOGTE INSTITUTE OF TECHNO LOGY
Presentation on
Catalytic convertor
Presented by:
Prasad P. Manolkar [1115]
Prasanna Revenkar [1116]

2. CATALYTIC CONVERTOR

3. Contents:
 Introduction
 Construction
 Working
 Types
 Diesel Engine
 Installation
 Damage
 Environmental Impact

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 Introduction:
A catalytic convertor is a vehicle emission control device that converts toxic
pollutants in exhaust gas to less toxic pollutants by catalyzing a redox
reaction.
Catalytic convertors are used in internal combustion engines fueled by either
petrol(gasoline) or diesel.
Invented by:
Eugene Houndry
Year of invention:
1950

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Construction:
 The catalyst support:
The core is usually a ceramic monolith with a honey comb structure.
 The Wash coat:
A wash coat is a carrier for the catalytic materials & is used to disperse the
materials over large surface area.
 The catalysts:
The catalyst itself is made up of mixtures of precious metals such as platinum,
palladium, rhodium etc…
Rhodium is used as reduction catalyst.
Palladium is used as oxidation catalyst.
Platinum is used as both for reduction & oxidation
Catalyst.

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Working:
 Due to partial combustion, gases such as oxides of nitrogen, carbon monoxide
& un burnt hydrocarbons enter the catalytic convertor through the exhaust valve.
 There are basically two ceramic blocks,
ceramic block 1 contains platinum & rhodium and ceramic block 2
contains platinum and palladium as catalyst.
 As toxic gases enter 1st ceramic block oxides of nitrogen are 1st to react.
1. 2NOx  xO2 +N2
 The N2,O2,CO,HC enters the 2nd ceramic block.
1. 2CO+O2  2CO2
2. HC + O2  H2O + CO2

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Types:-
Two-way:
Involves two types of oxidation reaction
1. Oxidation of carbon monoxide to carbon-di-oxide
2CO+O2  2CO2
2. Oxidation of hydrocarbons
CxH2x+2+ [(3x+1)/2] O2  xCO2+(x+1) H2O (combustion reaction)

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Three-way:-
Oxidation-reduction reaction’s
1. Reduction of oxides to nitrogen & oxygen:
2NOx – xO2 +N2
2. Oxidation of carbon monoxide to carbon-di-oxide:
2CO+O2 – 2CO2
3. Oxidation of un burnt hydrocarbons:
CxH2x+2 + [(3x+1)/2] O2 – xCO2 + (x+1) H2O

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Diesel engine’s:
For diesel engines the most common catalyst used is oxygen.
In exhaust gas stream to convert carbon monoxide to carbon-di-oxide
& hydrocarbons to water & carbon-di-oxide.
These convertors often operate at 90% efficiency.

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Installation:
Many vehicles have a close-coupled catalytic converter located near
the engine's exhaust manifold.
This unit heats up quickly due to its proximity to the engine,
and reduces cold-engine emissions by burning off hydrocarbons from
the extra-rich mixture used to start a cold engine

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Damage :
Catalyst poisoning occurs when the catalytic convertor is exposed to
exhaust containing substance that coat the working surfaces, encapsulating
the catalyst so that it cannot contact & treat the exhaust.
The most notable contaminant is lead.
Vehicles equipped with catalytic Convertor can be run only
on unleaded fuels.
Vehicles equipped with OBD-II diagnostic systems are designed to alert
The driver the misfire condition by means of flashing the check engine
Light on the dashboard.

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Environmental impact:
 Catalytic convertors have proven to be reliable & effective in reducing of
toxic emissions. However, these also have adverse environmental impacts
in production.
 If a three-way catalyst must run at the stoichiometric point, means the
Fuel is consumed than in the lean burn engine.
This means app. 10% more CO2 is emitted.

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