The role of Bronstead acidity in poisoning the SCR-urea reaction over FeZSM-5 catalysts

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Title: The role of Bronstead acidity in poisoning the SCR-urea reaction over FeZSM-5 catalysts
Authors: Sullivan, James A.
Keane, Orla
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Date: Nov-2005
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
Copyright (published version): 2005 Elsevier B.V.
Keywords: FeZSM-5deNOxUreaNH3TPD
DOI: 10.1016/j.apcatb.2005.06.001
Language: en
Status of Item: Peer reviewed
Appears in Collections:Chemistry Research Collection

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