Effects of H<sub>2</sub>O, CO<sub>2</sub>, CO, and Flow Rates on the RF-Based Monitoring of Three-Way Catalysts

Reiß, Sebastian; Wedemann, Marion; Spörl, Matthias; Fischerauer, Gerhard; Moos, Ralf

doi:10.1166/sl.2011.1472

Cited by 26 publications

(23 citation statements)

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“…They broaden the S 11 curve and shift the resonance frequency [15]. The system is insensitive to other exhaust components like H 2 , CO 2 or CO [20]. However, since the size of the cavity as well as the electrical conductivity of the catalyst materials depends on temperature, temperature effects on the resonance frequency have to be compensated [21].…”

Section: The Microwave Cavity Perturbation Techniquementioning

confidence: 99%

Effect of propene, propane, and methane on conversion and oxidation state of three-way catalysts: a microwave cavity perturbation study

Beulertz

Votsmeier

Moos

2015

Applied Catalysis B: Environmental

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Section: The Microwave Cavity Perturbation Techniquementioning

confidence: 99%

Effect of propene, propane, and methane on conversion and oxidation state of three-way catalysts: a microwave cavity perturbation study

Beulertz

Votsmeier

Moos

2015

Applied Catalysis B: Environmental

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“…Instead, they are intended to detect the status of full-sized exhaust gas aftertreatment devices during operation on the road. Typical applications are the determination of the oxygen loading of three-way catalytic converters (Moos et al, 2008Beulertz et al, 2013;Reiß et al, 2011a), or the soot loading (Sappok et al, 2010;Feulner et al, 2013) or ash loading (Kulkarni et al, 2013) of fullsized diesel particulate filters. The storage degree of NO in lean NO x traps (Fremerey et al, 2011;Moos et al, 2009) and the NH 3 loading on SCR catalyst devices have also been successfully monitored (Reiß et al, 2011b;Rauch et al, 2014Rauch et al, , 2015 using the cavity perturbation method.…”

Section: Introductionmentioning

confidence: 99%

Ammonia storage studies on H-ZSM-5 zeolites by microwave cavity perturbation: correlation of dielectric properties with ammonia storage

Dietrich

Rauch

Simon

et al. 2015

J. Sens. Sens. Syst.

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Abstract.To meet today's emission standards, the ammonia-based selective catalytic reduction (SCR) has become the major NO x control strategy for light and heavy diesel engines. Before NO x reduction can proceed, adsorption of ammonia on the acidic sites of the catalyst is necessary. For improvements in efficiency and control of the exhaust gas aftertreatment, a better understanding of the ammonia storage on the acidic sites of zeolite-based SCR catalysts is needed. Thereby, the correlation of dielectric properties of the catalyst material itself with the ammonia storage is a promising approach. Recently, a laboratory setup using microwave cavity perturbation to measure the dielectric properties of catalyst material has been described. This study shows the first experimental data on zeolite-based SCR materials in their H-form. The SCR powder samples are monitored by microwave cavity perturbation while storing and depleting ammonia, both with and without admixed NO x at different temperatures. Its complex dielectric permittivity is found to correlate closely with the stored mass of ammonia. The influence of the temperature and the Si / Al ratio of the zeolite to the ammonia storage behavior are also examined. These measurements disclose different temperature dependencies and differing sensitivities to ammonia storage for both real and imaginary parts of the complex permittivity. The apparent constant sensitivity of the real part can be related to the polarity of the adsorbed ammonia molecules, whereas the imaginary part depends on the Si / Al ratio and is related to the conductivity mechanisms of the zeolite material by proton hopping. It provides information about the zeolite structure and the number of (and the distance between) acidic storage sites, in addition to the stored ammonia mass.

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“…This has been shown by careful titrations in the engine dynamometer as well as in the lab test bench (Reiß et al, 2011a, b). The system is not sensitive to other exhaust components such as H 2 , CO 2 , or CO (Reiß et al, 2011c). However, as both the size of the cavity and Return loss |S 11 | of a canned TWC in the frequency range in which the two lowest-order cavity modes resonate and at approximately 450°C.…”

Section: Application To Three-way Catalystsmentioning

confidence: 99%

“…In TWC, a marked resonance frequency change can be found as well. For a platinum-coated, ceria-zirconiacontaining TWC (diameter 4.66" 9 5") at 450°C, F can reach values of almost 300 ppm/% oxygen load (Reiß et al, 2011c). Since the resonance frequency change strongly depends on the effective conductivity change of the catalyst or filter material, it becomes clear that a system like a DPF, in which the conductivity changes by orders of magnitude from almost zero to a very high value because of soot loading, shows a much more pronounced response than a ceria-zirconia coated cordierite substrate (TWC).…”

Section: Comparison Of the Magnitude Of The Resonance Frequency Changmentioning

confidence: 99%

Automotive Catalyst State Diagnosis Using Microwaves

Moos

Fischerauer

2014

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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-The state of catalysts plays a key role in automotive exhaust gas aftertreatment. The soot or ash loading of Diesel particulate filters, the oxygen loading degree in three-way catalysts, the amount of stored ammonia in SCR catalysts, or the NO x loading degree in NO x storage catalysts are important parameters that are today determined indirectly and in a model-based manner with gas sensors installed upstream and/or downstream of the catalysts. This contribution gives an overview on a novel approach to determine the catalyst state directly by a microwave-based technique. The method exploits the fact that the catalyst housing acts as a microwave cavity resonator. As "sensing" elements, one or two simple antennas are mounted inside the catalyst canning. The electrical properties of the catalyst device (ceramic honeycomb plus coating and storage material) can be measured. Preferably, the resonance characteristics, e.g., the resonance frequencies, of selected cavity modes are observed. The information on the catalyst interior obtained in such a contactless manner is very well correlated with the catalyst state as will be demonstrated for different exhaust gas aftertreatment systems.Re´sume´-Diagnostic de l'e´tat de catalyseurs d'automobiles a`l'aide de micro-ondes -L'e´tat des catalyseurs joue un roˆle essentiel dans le post-traitement des gaz d'e´chappement automobiles. Le chargement en suie ou en cendres des filtres Diesel a`particules, la teneur en oxyge`ne dans les catalyseurs trois voies, la quantite´d'ammoniac stocke´e dans les catalyseurs SCR ou le niveau de chargement en NO x dans les catalyseurs de stockage de NO x sont des parame`tres importants de´termine´s aujourd'hui de manie`re indirecte et sur la base de mode`les avec des capteurs de gaz se trouvant en amont et/ou en aval des catalyseurs. Cette contribution pre´sente une nouvelle approche permettant de de´terminer l'e´tat du catalyseur, directement en utilisant une technique a`micro-ondes. La me´thode exploite le fait que le boıˆtier du catalyseur agit comme cavite´re´sonnante de micro-ondes. En tant qu'e´le´ments de de´tection, une ou deux antennes simples sont installe´es a`l'inte´rieur du conditionnement du catalyseur. Les proprie´te´s e´lectriques du dispositif catalytique (nid d'abeille en ce´ramique plus reveˆtement et mate´riau de stockage) peuvent eˆtre mesure´es. De pre´fe´rence, les caracte´ristiques de re´sonnance, par exemple les fre´quences de re´sonnance, des modes de cavite´se´lectionne´s, sont observe´es. Les donne´es obtenues de cette manie`re sans contact, sont tre`s bien corre´le´es avec l'e´tat du catalyseur, tel que cela sera de´montre´pour diffe´rents syste`mes de post-traitement des gaz d'e´chappement.

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Effects of H₂O, CO₂, CO, and Flow Rates on the RF-Based Monitoring of Three-Way Catalysts

Cited by 26 publications

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Effect of propene, propane, and methane on conversion and oxidation state of three-way catalysts: a microwave cavity perturbation study

Effect of propene, propane, and methane on conversion and oxidation state of three-way catalysts: a microwave cavity perturbation study

Ammonia storage studies on H-ZSM-5 zeolites by microwave cavity perturbation: correlation of dielectric properties with ammonia storage

Automotive Catalyst State Diagnosis Using Microwaves

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Effects of H2O, CO2, CO, and Flow Rates on the RF-Based Monitoring of Three-Way Catalysts

Cited by 26 publications

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Effect of propene, propane, and methane on conversion and oxidation state of three-way catalysts: a microwave cavity perturbation study

Effect of propene, propane, and methane on conversion and oxidation state of three-way catalysts: a microwave cavity perturbation study

Ammonia storage studies on H-ZSM-5 zeolites by microwave cavity perturbation: correlation of dielectric properties with ammonia storage

Automotive Catalyst State Diagnosis Using Microwaves

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Product

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Effects of H₂O, CO₂, CO, and Flow Rates on the RF-Based Monitoring of Three-Way Catalysts