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The State of the Iron Promoter in Tungstated Zirconia Catalysts
Author(s) -
Carrier Xavier,
Lukinskas Povilas,
Kuba Stefan,
Stievano Lorenzo,
Wagner Friedrich E.,
Che Michel,
Knözinger Helmut
Publication year - 2004
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200400046
Subject(s) - x ray absorption spectroscopy , catalysis , dehydrogenation , inorganic chemistry , electron paramagnetic resonance , chemistry , mössbauer spectroscopy , oxidation state , iron oxide , absorption spectroscopy , redox , crystallography , organic chemistry , nuclear magnetic resonance , physics , quantum mechanics
The activity and selectivity of tungstated zirconia (WZ) for the conversion of n ‐ into isopentane are dramatically enhanced when the catalyst is modified with Pt and Fe. The state of iron in these catalysts was hitherto only poorly characterized. Therefore, in the present work we investigated the structural and electronic properties of iron in WZ catalysts containing 1 wt % Pt and 1 wt % Fe 2 O 3 , by a combination of spectroscopic techniques, namely X‐ray absorption spectroscopy (XAS), in situ electron paramagnetic resonance (EPR), and Mössbauer spectroscopy. In the oxidized catalyst, iron is present as Fe III and predominantly forms a surface solid solution in which the isolated Fe III ions are located in a distorted octahedral environment. A small amount of the total iron (around 10 %) is present in the form of small iron oxide particles. Both iron species can be reduced in H 2 and then easily reoxidized on exposure to air at room temperature. We infer that the promoter action of iron in these catalysts is intimately related to its redox properties and specifically affects the dehydrogenation activity of the materials.