Catalysts as sensors--a promising novel approach in automotive exhaust gas aftertreatment

Sensors that detect directly and in situ the status of automotive exhaust gas catalysts by monitoring the electrical properties of the catalyst coating itself are overviewed. Examples included in this review are the in-situ determination of the electrical impedance of three-way catalysts based on ce...

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Bibliographic Details
Published in:Sensors (Basel, Switzerland) Switzerland), 2010-07, Vol.10 (7), p.6773-6787
Main Author: Moos, Ralf
Format: Article
Language:English
Subjects:
ammonia SCR
Catalysis
Electromagnetic Fields
lambda probe
lean NOx trap (LNT)
microwave
on-board diagnosis (OBD)
Review
three-way catalyst (TWC)
Vehicle Emissions
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Summary:Sensors that detect directly and in situ the status of automotive exhaust gas catalysts by monitoring the electrical properties of the catalyst coating itself are overviewed. Examples included in this review are the in-situ determination of the electrical impedance of three-way catalysts based on ceria-zirconia solutions and of lean NO(x) traps of earth-alkaline based coatings, as well as approaches to determine the ammonia loading in Fe-SCR-zeolites with electrical ac measurements. Even more sophisticated approaches based on interactions with electromagnetic waves are also reviewed. For that purpose, metallic stick-like antennas are inserted into the exhaust pipe. The catalyst properties are measured in a contactless manner, directly indicating the catalyst status. The radio frequency probes gauge the oxygen loading degree of three-way catalysts, the NO(x)-loading of lean NO(x) traps, and the soot loading of Diesel particulate filters.
ISSN:1424-8220
1424-8220
DOI:10.3390/s100706773