Abstract
Many electrochemical reactions occur at high temperatures and inside bulk materials. Because of the difficulties associated with a direct observation of the reaction, one often resorts to indirect measurement strategies. An example is the three-way catalyst (TWC) in the exhaust pipe of a gasoline engine which stores oxygen when it is abundant in the exhaust gas and releases it later to oxidize noxious gas components such as CO in oxygen-deficient (“lean”) exhaust gases. Currently, the oxygen loading of the TWC is derived indirectly from the output signals of two lambda probes, one upstream and the other downstream of the catalyst, which monitor the air-to-fuel ratio λ in the exhaust gas. We have investigated a microwave cavity perturbation approach towards the direct measurement of the catalyst state. It will be shown that the uptake or release of oxygen in the catalyst is observable in situ via the S-parameters of a cavity resonator.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
References
C. Zimmermann, Neuartiger Sensor zur Bestimmung des Zustandes eines NOx-Speicherkatalysators (Ph.D. thesis, in German). Shaker, Aachen 2007
HM. Altschuler Dielectric constant. in Handbook of Microwave Measurements, vol. II, 3rd edn ed. by M. Sucher, J. Fox (Polytech. Inst. Brooklyn, Brooklyn 1963), pp. 495–548
SH. Chao, Measurements of microwave conductivity and dielectric constant by the cavity perturbation method and their errors IEEE Trans. MTT 33, 519–526 (1985)
R. Moos, M. Spörl, G. Hagen, A. Gollwitzer, M. Wedemann, G. Fischerauer, TWC: lambda control and OBD without lambda probe – an initial approach. SAE Technical Paper Series No. 2008–01–0916 (2008)
G. Fischerauer, M. Spörl, A. Gollwitzer, M. Wedemann, R. Moos, Catalyst state observation via the perturbation of a microwave cavity resonator. Frequenz 62, 180–184 (2008)
G. Fischerauer, A. Gollwitzer, A. Nerowski, M. Spörl, R. Moos, On the inverse problem associated with the observation of electrochemical processes by the RF cavity perturbation method. in Proceedings of SSD’09, Djerba (2009)
P.S. Neelakanta, Handbook of Electromagetic Materials (CRC Press, Boca Raton, 1995)
G. Roussy, J.M. Thiebaut, F. Ename-Obiang, E. Marchal, Microwave broadband permittivity measurement with a multimode helical resonator for studying catalysts. Meas. Sci. Technol. 12, 542–547 (2001)
H.L. Tuller , A.S. Nowick, Defect structure and electrical properties of nonstoichiometric CeO2 single crystals. J. Electrochem. Soc. 126, 209–217 (1979)
P. Jasinski, T. Suzuki, H.U. Anderson, Nanocrystalline undoped ceria oxygen sensor. Sens Actuators B bf 95, 73–77 (2003)
R.F. Harrington, Time-Harmonic Electromagetic Fields (McGraw-Hill, New York, 1961)
Acknowledgements
This work was supported by the German Research Foundation (DFG), grants number Fi 956/3–1 and Mo 1060/6–1. The authors are indebted to Drs. Ulrich Göbel, Jürgen Gieshoff, and Martin Rösch from Umicore, Hanau, Germany who provided TWC samples.
Author information
Authors and Affiliations
Corresponding author
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2011 Springer-Verlag Berlin Heidelberg
About this chapter
Cite this chapter
Fischerauer, G., Gollwitzer, A., Nerowski, A., Spörl, M., Reiß, S., Moos, R. (2011). Monitoring of Electrochemical Processes in Catalysts by Microwave Methods. In: Lindenmeier, S., Weigel, R. (eds) Electromagnetics and Network Theory and their Microwave Technology Applications. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-18375-1_9
Download citation
DOI: https://doi.org/10.1007/978-3-642-18375-1_9
Published:
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-642-18374-4
Online ISBN: 978-3-642-18375-1
eBook Packages: EngineeringEngineering (R0)