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          Institute: Fritz-Haber-Institut     Collection: Inorganic Chemistry     Display Documents

ID: 299668.3, Fritz-Haber-Institut / Inorganic Chemistry
The structural genesis of a complex (MoVW)5O14 oxide during thermal treatments and its redox behavior at elevated temperatures
Authors:Zenkovets, Galina A.; Kryukova, Galina N.; Gavrilov, Vladimir Yu.; Tsybulya, Sergei V.; Anufrienko, Vladimir A.; Larina, Tatiana A.; Khabibulin, Dzhalil F.; Lapina, Olga B.; Rödel, Eva; Trunschke, Annette; Ressler, Thorsten; Schlögl, Robert
Research Context:4, Molybdates in C3 selective oxidations
Date of Publication (YYYY-MM-DD):2007
Title of Journal:Materials Chemistry and Physics
Journal Abbrev.:Mat. Chem. Phys.
Issue / Number:2-3
Start Page:295
End Page:304
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:The structural genesis of a Mo0.68V0.23W0.09 oxide with Mo5O14-like structure has been examined. A precursor prepared by spray-drying of mixed aqueous metal salt solutions was calcined in air and subsequently treated in helium at different temperatures. X-ray diffraction, HRTEM, 51V MAS NMR, ESR, UV/Vis DR spectroscopy and oxygen and hydrogen adsorption measurements have been applied to monitor the preparation procedure. It was found that a structure closely related to that of Mo5O14 already appears at nano-scale level after calcination of the spray-dried precursor in air at 350°C. At this stage, the material comprises of crystalline particles less than 3 nm in size stabilized by an amorphous matrix. Further heating causes nano-structural rearrangements that lead to the formation of the final Mo0.68V0.23W0.09 oxide with phase-pure polycrystalline structure. Molybdenum and tungsten ions are hexavalent and coordinated in an octahedral environment. Furthermore, vanadium is present as V4+ and V5+ ions which partially occupy octahedral sites, whereas highly distorted trigonal pyramidal sites could be accommodated in pentagonal bipyramids of the Mo5O14 structure, however, displaced away from the center. According to the results of H2 and O2 adsorption the crystalline ternary oxide does not possess accessible micropores. Oxygen pulses at 450oC and reductive treatment with pure hydrogen at 300oC did not cause noticeable changes of the bulk structure thus indicating a remarkable structural stability of the complex MoVW oxide under redox conditions at elevated temperature.
Free Keywords:Nanostructures, molybdenum oxide, Mo5O14, electron microscopy
External Publication Status:published
Document Type:Article
Communicated by:Robert Schlögl
Affiliations:Fritz-Haber-Institut/Inorganic Chemistry/Preparation
Fritz-Haber-Institut/Inorganic Chemistry/Geometric Structure
Fritz-Haber-Institut/Inorganic Chemistry/Inorganic Chemistry
External Affiliations:Boreskov Institute of Catalysis of SB RAS, pr. Lavrentieva 5, 630090 Novosibirsk, Russia
Identifiers:URL:http://dx.doi.org/10.1016/j.matchemphys.2007.02.02... [only for subscriber]
URL:http://www.sciencedirect.com/science?_ob=ArticleUR... [only for subscriber]
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