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The three-way catalytic converter
This extract is concerned primarily with the chemistry that underpins the operation of...
This extract is concerned primarily with the chemistry that underpins the operation of the three-way catalytic converter that is placed in the exhaust systems of motor vehicles in order to reduce the emissions of primary pollutants: carbon monoxide, oxides of nitrogen and volatile organic compounds, including hydrocarbons. Discussion of the various effects of these pollutants and the consequent introduction and refinement of ‘automotive emission regulations’ has not been included, nor is there a look forward to future research trends. These topics are covered in the original Case Study.
Having read this unit you should be able to:
- discuss how the gas mixture expelled from the engine, and the conversion performance of the three-way catalytic converter, depend on the air/fuel (A/F) ratio;
- list the chemical reactions whereby the three-way catalyst removes carbon monoxide (CO), hydrocarbons and oxides of nitrogen (NOx) from petrol vehicle exhausts;
- interpret the results of experimental studies (involving activity tests, kinetic measurements, adsorption studies and/or various surface science techniques) of the three-way catalyst and appropriate model systems;
- discuss possible mechanisms for the catalytic reactions removing CO, hydrocarbons and NOx from vehicle exhausts;
- outline the modes of deterioration of the three-way catalyst, and comment on the strategies that could be used to reduce H2S emissions.
- Current section: Introduction
- Learning outcomes
- 1. Overview
- 4.1 Exhaust pollutants
- 4.2 The three-way catalytic converter
- 4.3 Exhaust emission characteristics
- 4.4 The chemical reactions
- 4.5 Catalyst deterioration
The three-way catalytic converter
Ensuring good quality air is essential for the protection of public health. Governments worldwide have adopted a range of increasingly demanding measures to curb air pollution with a particular focus on the emissions from motor vehicles. An important part of this strategy has been the development of the three-way catalytic converter to remove exhaust pollutants such as carbon monoxide, unburnt hydrocarbons and nitrogen oxides. This unit takes an in-depth look at the construction of this converter for petrol-driven vehicles and investigates the catalytic chemistry taking place at the molecular level. It is assumed that you already have a scientific background.
This unit is from our archive and is an adapted extract from Principles of chemical change (S342) which is no longer taught by The Open University. If you want to study formally with us, you may wish to explore other courses we offer in.
This is an extract from an Open University course which is no longer available to new students. If you found this interesting you could explore more free Chemistry course units or view the range of currently available OU Chemistry courses.