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The role of Bronstead acidity in poisoning the SCR-urea reaction over FeZSM-5 catalysts
Author(s)
Date Issued
2005-11
Date Available
2013-01-07T15:55:35Z
Abstract
Two series of FeZSM-5 catalysts prepared from Na+ and NH4+ ZSM-5 precursors are studied in the selective reduction of NOx using NH3 and urea as reducing agents. All Fe-containing catalysts are active for NOx reduction in the SCR-NH3 reaction with ex-NH4+ catalysts being more active than ex-Na+ materials and the activity depending (to a minor extent within each series of catalysts) upon [Fe]. Catalysts with Bronstead acid sites also show a small transient deNO(x) activity at low temperatures. All catalysts are less active for the SCR-urea reaction but the ex-Na+ catalysts retain far more deNO(x) activity than the ex-NH4+ materials. NH3 TPD shows that strongly binding Bronstead acid sites are present on the ex-NH4+ materials and H+-treated parent zeolites while Urea TPD shows that the mode of decomposition of urea differs as a function of initial zeolite counter-ion. Urea TPSR shows that the reaction between adsorbed urea and gaseous NO/O-2 is related to [Fe]. It is proposed that the decreased activity of the ex-NH4(+) catalysts in the SCR-urea reaction is due to a less favourable mode of decomposition over these catalysts. Furthermore it is suggested that the Bronstead acidity plays some part in this less favoured decomposition.
Type of Material
Journal Article
Publisher
Elsevier
Journal
Applied Catalysis B: Environmental
Volume
61
Issue
3 -4
Start Page
244
End Page
252
Copyright (Published Version)
2005 Elsevier B.V.
Language
English
Status of Item
Peer reviewed
This item is made available under a Creative Commons License
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