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Operando XAS/XRD and Raman Spectroscopic Study of Structural Changes of the Iron Molybdate Catalyst during Selective Oxidation of Methanol

Gaur, Abhijeet; Schumann, Max; Raun, K. V.; Stehle, Matthias; Beato, P.; Jensen, A. D.; Grunwaldt, Jan-Dierk; Høj, M.

Abstract:
The structural changes of an iron molybdate/molybdenum oxide (Mo/Fe=2.0) catalyst for the selective oxidation of methanol to formaldehyde were studied using combined operando X‐ray absorption spectroscopy (XAS) and X‐ray diffraction (XRD) as well as operando Raman spectroscopy. Under operating conditions, the Mo K‐edge XANES spectra showed a transition from a mixture of α‐MoO$_{3}$ and Fe$_{2}$(MoO$_{4}$)$_{3}$ towards only Fe$_{2}$(MoO$_{4}$)$_{3}$. XRD and Raman spectroscopy also showed disappearance of the α‐MoO3 phase with time on stream. The results evidenced that the α‐MoO3 component evaporated completely, while the Fe$_{2}$(MoO$_{4}$)$_{3}$ component remained stable. This was linked to a decrease in catalytic activity. Further studies unraveled that the rate of α‐MoO$_{3}$ evaporation increased with increasing MeOH concentration, decreasing O$_{2}$ concentration and increasing temperature. The simultaneous measurements of catalytic activity and spectroscopy allowed to derive a structure‐activity relationship showing that α‐MoO$_{3}$ evaporation needs to be prevented to optimize MoO$_{3}$‐based catalysts for selective oxidation of methanol.

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Postprint §
DOI: 10.5445/IR/1000098420
Veröffentlicht am 08.01.2020
Originalveröffentlichung
DOI: 10.1002/cctc.201901025
Scopus
Zitationen: 7
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Zitationen: 7
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Zugehörige Institution(en) am KIT Institut für Katalyseforschung und -technologie (IKFT)
Institut für Technische Chemie und Polymerchemie (ITCP)
Publikationstyp Zeitschriftenaufsatz
Publikationsdatum 07.10.2019
Sprache Englisch
Identifikator ISSN: 1867-3880, 1867-3899
KITopen-ID: 1000098420
HGF-Programm 37.03.01 (POF III, LK 01) Catalysts and Mechanisms
Erschienen in ChemCatChem
Verlag Wiley-VCH Verlag
Band 11
Heft 19
Seiten 4871-4883
Vorab online veröffentlicht am 15.07.2019
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