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ABSTRACT
Within the domain of transports and more specifically the automobile sector, mechanical energy is mainly produced by internal combustion engines. Over the last few years, combustion process technology has massively evolved as well as fuel specifications. However, aside of carbon dioxide, water, nitrogen and oxygen, a significant number of pollutants are still to be found in vehicles exhausts. Acknowledgment of the harmful effects on health induced by gaseous and particulate emissions has led to global regulation and the usage of after-treatment devices such as catalysts and filters. The role of chemistry is essential in reducing the amount of polluting molecules within catalytic mechanisms . In the case of positive-ignition engines, residual gases contain as many oxidant species as reducing ones. Post-treatment can thus be successfully carried out by means of a three-way catalyst.
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Read the articleAUTHORS
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Alain SASSI: Doctor of Chemistry - Head of the Chemistry of Pollution Control Systems Department at PSA Peugeot Citroën
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Emmanuel ROHART: Doctorate in Chemical Engineering - Head of materials development for automotive catalysis, Rhodia Rare Earths Systems
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Gérard BELOT: Doctor of Physical Sciences - Independent consultant in automotive technology, specializing in Energy, Combustion, Emissions
INTRODUCTION
The main anthropogenic sources of atmospheric pollutants are: transport, energy production, industry, housing, agriculture...
In the case of transport, and more specifically automobiles, mechanical energy is produced by internal combustion engines (gasoline and diesel) for which the combustion processes, although constantly optimized, remain incomplete.
In addition to carbon dioxide, water, nitrogen, oxygen and heat, regulated pollutants include hydrocarbons (unburned or partially transformed fuel), carbon monoxide (CO), nitrogen oxides (NOx = NO + NO 2 ), particulate matter (PM = Particulate Matter) and unregulated pollutants such as nitrogen dioxide NO 2 , nitrous oxide (N 2 O), polycyclic aromatic hydrocarbons (PAHs), sulfur dioxide (SO 2 ), aldehydes (regulated in the USA), ketones...
Recognition of the harmful effects of gaseous and particulate emissions on health has led to the introduction of regulations (see
The history of post-processing is punctuated by key events that often preceded global regulations:
– United States: 1975, oxidation catalysis for petrol vehicles;
1981, 3-way catalytic converter for petrol vehicles ;
– Japan: 1980, 3-way catalysis for petrol vehicles;
1985, DeNOx catalysis for lean-burn petrol vehicles;
– in Europe: 1992, 3-way catalytic converter for petrol vehicles;
1995, oxidation catalysis for diesel vehicles;
2000, particulate filter with fuel additive for diesel vehicles ;
2003, catalyzed filter for diesel vehicles.
These devices for the after-treatment of gaseous and particulate emissions from internal combustion engines are described conceptually and functionally in this article and the next
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