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


Dietrich, Markus ; Rauch, Dieter ; Simon, Ulrich ; Porch, Adrian ; Moos, Ralf:
Ammonia storage studies on H-ZSM-5 zeolites by microwave cavity perturbation: correlation of dielectric properties with ammonia storage.
In: Journal of Sensors and Sensor Systems. Bd. 4 (2015) Heft 2 . - S. 263-269.
ISSN 2194-878X
DOI: 10.5194/jsss-4-263-2015


Link zum Volltext (externe URL): Volltext

Angaben zu Projekten

Offizieller ProjekttitelProjekt-ID
Ohne AngabeMo 1060/19-1

Projektfinanzierung: Deutsche Forschungsgemeinschaft


To meet today's emission standards, the ammonia-based selective catalytic reduction (SCR) has become the major NOx control strategy for light and heavy diesel engines. Before NOx 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 NOx 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.
The effect of stored ammonia on the complex dielectric permittivity of H-ZSM-5 zeolites with varying storage site density was observed between 200 and 300 °C under reaction conditions by microwave cavity perturbation. Polarization and dielectric losses were differently affected. The sensitivity of the polarization to stored ammonia is almost independent, the sensitivity of the dielectric losses strongly dependent on the storage site density. The results can be explained by proton hopping.

Weitere Angaben

Publikationsform: Artikel in einer Zeitschrift
Begutachteter Beitrag: Ja
Institutionen der Universität: Fakultäten > Fakultät für Ingenieurwissenschaften
Fakultäten > Fakultät für Ingenieurwissenschaften > Lehrstuhl Funktionsmaterialien > Lehrstuhl Funktionsmaterialien - Univ.-Prof. Dr.-Ing. Ralf Moos
Forschungseinrichtungen > Forschungsstellen > ZET - Zentrum für Energietechnik
Forschungseinrichtungen > Forschungsstellen > BERC - Bayreuth Engine Research Center
Fakultäten > Fakultät für Ingenieurwissenschaften > Lehrstuhl Funktionsmaterialien
Forschungseinrichtungen > Forschungsstellen
Profilfelder > Advanced Fields > Neue Materialien
Forschungseinrichtungen > Forschungszentren > Bayreuther Materialzentrum - BayMAT
Profilfelder > Advanced Fields
Forschungseinrichtungen > Forschungszentren
Titel an der UBT entstanden: Ja
Themengebiete aus DDC: 600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften
Eingestellt am: 21 Sep 2015 12:59
Letzte Änderung: 18 Apr 2016 07:27
URI: https://eref.uni-bayreuth.de/id/eprint/19469