Chemical Anchoring of Palladium by Fe Oxo Ions in Zeolite ZSM-5

Zeolite supported mono- and bimetallic catalysts Pd/ZSM-5 and PdFe/ZSM-5 were prepared by exchanging Pd from a dilute aqueous solution of [Pd(NH3)4](NO3)2 into either H/ZSM-5 or Fe/ZSM-5. The Fe/ZSM-5 was prepared by sublimation; it contains a major part of the Fe as dinuclear oxygen-bridged Fe3+ io...

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Bibliographic Details
Published in:The journal of physical chemistry. B 2002-08, Vol.106 (30), p.7520-7523
Main Authors: Wen, Bin, Jia, Jifei, Sachtler, Wolfgang M. H
Format: Article
Language:English
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Summary:Zeolite supported mono- and bimetallic catalysts Pd/ZSM-5 and PdFe/ZSM-5 were prepared by exchanging Pd from a dilute aqueous solution of [Pd(NH3)4](NO3)2 into either H/ZSM-5 or Fe/ZSM-5. The Fe/ZSM-5 was prepared by sublimation; it contains a major part of the Fe as dinuclear oxygen-bridged Fe3+ ions. Significant differences between Pd/ZSM-5 and PdFe/ZSM-5 are revealed after calcination:  in Pd/ZSM-5 the Pd is present as large PdO particles, but in PdFe/ZSM-5 it is highly dispersed over the zeolite cavities and invisible in TEM. Evidently, the Fe ions and/or Fe oxo ions act as very effective chemical anchors. It is argued that Pd0 is formed by autoreduction of [Pd(NH3)4]2+ ions even under calcination conditions. The Fe ions promote nucleation and limit growth of Pd0 n clusters, which are subsequently converted to PdO.
ISSN:1520-6106
1520-5207
DOI:10.1021/jp020724s