Proton transport in Fe-ZSM-5 and Cu-ZSM-5 zeolites for NH3-SCR : the role of NH4NO3 intermediate

Titelangaben

Chen, Peirong ; Schönebaum, Simon ; Rauch, Dieter ; Moos, Ralf ; Simon, Ulrich:
Proton transport in Fe-ZSM-5 and Cu-ZSM-5 zeolites for NH3-SCR : the role of NH4NO3 intermediate.
2016
Veranstaltung: 49. Jahrestreffen Deutscher Katalytiker , 16. - 18. März 2016 , Weimar.
(Veranstaltungsbeitrag: Kongress/Konferenz/Symposium/Tagung , Poster )

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Abstract

Although numerous investigations have been performed to clarify the reaction mechanism of NH3-SCR over well-established zeolite catalysts, the role of proton transport, which is an elementary and crucial step in NH3-SCR, is not well understood and sometimes even ignored. Here, we performed in situ IS-DRIFTS (simultaneous impedance and diffuse reflection infrared Fourier transform spectroscopy) studies on highly comparable zeolites Fe-ZSM-5 and Cu-ZSM-5 (with the Cu or Fe species predominantly in isolated state) as catalysts under SCR-related conditions. Thereby we revealed for the first time the significantly different influence of Fe and Cu cations on the proton transport in ZSM-5 zeolite catalyst.

...

In summary, by means of IS-DRIFTS, we revealed that the proton transport in Fe-ZSM-5 depends on the amount of NH3-related surface species (i.e. NH4+ and weakly bound NH3 species), and the proton transport in Cu-ZSM-5 is dominated by the NH4NO3 intermediate resulting from the interaction between NH4+ and activated NO on Cu sites. This molecular understanding of proton transport properties thus provides a new perspective on the interpretation of the different NH3-SCR performance of Fe-ZSM-5 and Cu-ZSM-5 zeolites at low temperatures.