Monitoring the Ammonia Loading of Zeolite‐Based Ammonia SCR Catalysts by a Microwave Method

Reiß, Sebastian; Schönauer, Daniela; Hagen, Gunter; Fischerauer, Gerhard; Moos, Ralf

doi:10.1002/ceat.201000546

Cited by 42 publications

(34 citation statements)

References 23 publications

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“…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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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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“…It has been known for many years that zeolites change their conductivity with ammonia loading (Simon et al, 1998;Rodrı´guez-Gonza´lez and Simon, 2010), but these effects are in the order of only half a magnitude. Therefore, it is astonishing that for SCR catalysts effects in the range of 50 ppm/% ammonia load occur at 300°C (Reiß et al, 2011d). In recent but yet unpublished work, we even found 80 ppm/% for serial type Cu-Chabazite zeolites at 200°C.…”

Section: Comparison Of the Magnitude Of The Resonance Frequency Changmentioning

confidence: 57%

“…This was investigated in literature (Reiß et al, 2011d) and will be summarized in the following section.…”

Section: Application To Nh 3 -Scr Catalystsmentioning

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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“…Besides TWC characterization, the transfer to other catalyst types such as lean NO x traps opens up a wide spectrum of possible OBD applications. Initial attempts for measuring the NO x loading of LNT were successful [56] as well as ammonia storage determination in SCR catalysts [54] or soot load detection in DPF [55].…”

Section: Radio Frequency-based Catalyst Gaugingmentioning

confidence: 99%

New Approaches for Exhaust Gas Sensing

Moos

2011

Springer Series on Chemical Sensors and Biosensors

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Steadily increasing emission standards for passenger cars and heavy duty vehicles combined with the need for fuel efficiency lead to novel powertrain concepts, for example to leanly operated gasoline direct injection engines, or to novel exhaust gas aftertreatment concepts such as Lean NO x Traps (LNT), ammonia selective catalytic reduction catalysts for NO x reduction (SCR), or even to a combination of both. Also, diesel particulate filters (DPF) are in series production.To control these novel exhaust gas aftertreatment systems and to monitor onboard the proper operation of these systems (on-board diagnosis, OBD), novel exhaust gas sensors are required or are at least be very helpful. Since the development of exhaust gas sensors has always to be seen in interaction with the corresponding exhaust gas aftertreatment systems, novel types of exhaust gas sensors have gained in importance just recently, when the time was ripe for novel exhaust gas aftertreatment concepts. This article reports on several types of NO x sensors and ammonia sensors.Additionally, a very recent novel concept is presented. Here, the catalyst itself works as a sensing device that gives directly information on its own status. The readout can be wirebound (demonstrated for LNT and SCR) or even be wireless by applying radio frequency techniques. It will be shown that this allows to detect the oxygen loading degree of three-way catalysts very precisely. It can be also applied to determine the ammonia loading of SCR catalysts and the soot loading of DPF.As a conclusion, these novel methods may provide a future alternative for low emission-aiming engine control as well as for OBD of low emission vehicles with novel exhaust gas aftertreatment systems. However, it is clear that all novel sensors or systems do not only have to meet the technical requirements but also have to be very inexpensive, reliable, and cost effective.R. Moos (*)

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Monitoring the Ammonia Loading of Zeolite‐Based Ammonia SCR Catalysts by a Microwave Method

Cited by 42 publications

References 23 publications

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

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

New Approaches for Exhaust Gas Sensing

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