Abstract
Knowledge of the actual catalyst state plays a key role in automotive exhaust gas aftertreatment. The oxygen loading degree of three-way catalysts (TWC), the amount of stored ammonia in selective reduction catalysts (SCR), or the NOx loading degree in NOx storage catalysts (NSC) are important parameters. Today, they are determined indirectly and/or model-based, applying models that are typically calibrated by gas sensors installed up- and/or downstream of the catalysts. A novel approach to determine directly the catalyst state by microwaves (radio frequencies, rf) emerged recently. For this method, the catalyst housing serves as an electrical cavity resonator. As “sensor”, one or two simple antennas are mounted in the canning. The electrical properties of the honeycomb incl. coating change with gas loading, affecting either the resonance frequencies or the power transmission. Such contactless-obtained information is strongly correlated with the catalyst state as will be discussed here for TWC and SCR systems. This contribution reviews the progress in the past 3 years that exceeds by far the status of initial studies.
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References
Moos R (2010) Catalysts as sensors—a promising novel approach in automotive exhaust gas aftertreatment. Sensors 10:6773–6787. doi:10.3390/s100706773
Sappok A, Bromberg L (2010) Loading and regeneration analysis of a diesel particulate filter with a radio frequency-based sensor. SAE paper 2010-01-2126. doi: 10.4271/2010-01-2126
Moos R, Wedemann M, Spörl M, Reiß S, Fischerauer G (2009) Direct catalyst monitoring by electrical means: an overview on promising novel principles. Top Catal 52:2035–2040. doi:10.1007/s11244-009-9399-6
Moos R, Beulertz G, Reiß S, Hagen G, Fischerauer G, Votsmeier M, Gieshoff J (2013) Overview: status of the microwave-based automotive catalyst state diagnosis. Top Catal 56:483–488. doi:10.1007/s11244-013-9980-x
Masoudi M, Sappok A (2014) Soot (PM) Sensors. DieselNet Technology Guide. http://www.dieselnet.com/tech/dpf_soot_sensors.php. Accessed 07 Aug 2014
Nanjundaswamy H, Nagaraju V, Wu Y, Koehler E, Sappok A, Ragaller P, Bromberg L (2015) Advanced rf particulate filter sensing and controls for efficient aftertreatment management and reduced fuel consumption. SAE Technical Paper 2015-01-0996, doi: 10.4271/2015-01-0996
Sappok A, Bromberg L (2014) Radio frequency diesel particulate filter soot and ash level sensors: enabling adaptive controls for heavy-duty diesel applications. SAE Int J Commer Veh 7:468–477. doi:10.4271/2014-01-2349
Beulertz G, Fritsch M, Fischerauer G, Herbst F, Gieshoff J, Votsmeier M, Hagen G, Moos R (2013) Microwave cavity perturbation as a tool for laboratory in situ measurement of the oxidation state of three way catalysts. Top Catal 56:405–409. doi:10.1007/s11244-013-9987-3
Moos R, Fischerauer G (2015) Automotive catalyst state diagnosis using microwaves. Oil Gas Sci Technol 70:55–65. doi:10.2516/ogst/2013203
Fischerauer G, Spörl M, Gollwitzer A, Wedemann M, Moos R (2008) Catalyst state observation via the perturbation of a microwave cavity resonator. Frequenz 62:180–184. doi:10.1515/FREQ.2008.62.7-8.180
Dietrich M, Jahn C, Lanzerath P, Moos R (2015) Microwave based oxidation state and soot loading determination on gasoline particulate filters with three-way catalyst coating for homogenously operated gasoline engines. Sensors 15:21971–21988. doi:10.3390/s150921971
Birkhofer T, Hofmann P, Knezevic A, Moos R, Plog C, Schneider R (2003) Verfahren zur Erkennung des Zustands eines Katalysators mittels Mikrowellen. German Patent Specification DE 10358495 B4
Moos R, Spörl M, Hagen G, Gollwitzer A, Wedemann M, Fischerauer G (2008) TWC: lambda control and OBD without lambda probe—an initial approach. SAE paper 2008-01-0916, doi: 10.4271/2008-01-0916
Reiß S, Wedemann M, Spörl M, Fischerauer G, Moos R (2011) Effects of H2O, CO2, CO, and flow rates on the RF-based monitoring of three-way catalysts. Sensor Letters 9:316–320. doi:10.1166/sl.2011.1472
Reiß S (2012) Direkte Zustandssensorik von Automobilabgaskatalysatoren (Direct diagnosis of automotive exhaust gas catalysts), Doctoral thesis, Universität Bayreuth
Möller R, Votsmeier M, Onder C, Guzzella L, Gieshoff J (2009) Is oxygen storage in three-way catalysts an equilibrium controlled process? Appl Catal B 91:30–38. doi:10.1016/j.apcatb.2009.05.003
Beulertz G, Votsmeier M, Herbst F, Moos R (2012) Replacing the lambda probe by radio frequency-based in-operando three-way catalyst oxygen loading detection. The 14th International Meeting on Chemical Sensors, IMCS 14, Nuremberg, Germany, 20–23 May 2012, pp 1426–1428, doi: 10.5162/IMCS2012/P2.2.7
Schödel S, Moos R, Votsmeier M, Fischerauer G (2014) SI-engine control with microwave-assisted direct observation of oxygen storage level in three-way catalysts. IEEE Trans Control Syst Technol 22:2346–2353. doi:10.1109/TCST.2014.2305576
Beulertz G, Votsmeier M, Moos R (2015) Effect of propene, propane, and methane on conversion and oxidation state of three-way catalysts: a microwave cavity perturbation study. Appl Catal B 165:369–377. doi:10.1016/j.apcatb.2014.09.068
Beulertz G, Votsmeier M, Moos R (2015) In operando detection of three-way catalyst aging by a microwave-based method: initial studies. Appl Sci 5:174–186. doi:10.3390/app5030174
Simons T, Simon U (2012) Zeolites as nanoporous, gas-sensitive materials for in situ monitoring of DeNOx-SCR. Beilstein J Nanotechnol 3:667–673. doi:10.3762/bjnano.3.76
Simon U, Franke ME (2000) Electrical properties of nanoscaled host/guest compounds. Microporous Mesoporous Mater 41:1–36. doi:10.1016/S1387-1811(00)00291-2
Franke ME, Simon U (2004) Solvate-supported proton transport in zeolites. Chem Phys Chem 5:465–472. doi:10.1002/cphc.200301011
Pihl J, Daw S (2014) NH3 storage isotherms: a path toward better models of NH3 storage on zeolite SCR catalysts. Presentation at 2014 DOE Crosscut Workshop on Lean Emissions Reduction Simulation
Rauch D, Kubinski D, Cavataio G, Upadhyay D, Moos R (2015) Ammonia loading detection of zeolite SCR catalysts using a radio frequency based method. SAE Int J Engines 8:1126–1135. doi:10.4271/2015-01-0986
Rauch D, Kubinski D, Simon U, Moos R (2014) Detection of the ammonia loading of a Cu Chabazite SCR catalyst by a radio frequency-based method. Sens Actuators B Chemical 205:88–93. doi:10.1016/j.snb.2014.08.019
Rauch D, Albrecht G, Kubinski D, Moos R (2015) A microwave-based method to monitor the ammonia loading of a vanadia-based SCR catalyst. Appl Catal B 165:36–42. doi:10.1016/j.apcatb.2014.09.059
Deutschmann O, Grunwaldt JD (2013) Abgasnachbehandlung in mobilen Systemen: stand der Technik, Herausforderungen und Perspektiven. Chemie Ingenieur Technik 85(5):1–24. doi:10.1002/cite.201200188
Donovan S, Klein O, Dressel M, Holczer K, Griiner G (1993) Microwave cavity perturbation technique: part II: experimental scheme. Int J Infrared Millimeter Waves 14:2459–2487. doi:10.1007/BF02086217
Dietrich M, Rauch D, Porch A, Moos R (2014) A laboratory test setup for in situ measurements of the dielectric properties of catalyst powder samples under reaction conditions by microwave cavity perturbation: set up and initial tests. Sensors 14:16856–16868. doi:10.3390/s140916856
Dietrich M, Rauch D, Simon U, Porch A, Moos R (2015) Ammonia storage studies on H-ZSM-5 zeolites by microwave cavity perturbation: correlation of dielectric properties with ammonia storage. J Sens Sens Syst 4:263–269. doi:10.5194/jsss-4-263-2015
Acknowledgments
R.M is indebted to the German Research Foundation (DFG) for financial support under Grant Numbers MO1060/13-1 and MO1060/19-1.
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Moos, R., Rauch, D., Votsmeier, M. et al. Review on Radio Frequency Based Monitoring of SCR and Three Way Catalysts. Top Catal 59, 961–969 (2016). https://doi.org/10.1007/s11244-016-0575-1
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DOI: https://doi.org/10.1007/s11244-016-0575-1