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  Molybdenum Oxide Based Partial Oxidation Catalyst: 3. Structural Changes of a MoVW Mixed Oxide Catalyst during Activation and Relation to Catalytic Performance in Acrolein Oxidation

Ovsitser, O., Uchida, Y., Mestl, G., Weinberg, G., Blume, A., Jäger, J., et al. (2002). Molybdenum Oxide Based Partial Oxidation Catalyst: 3. Structural Changes of a MoVW Mixed Oxide Catalyst during Activation and Relation to Catalytic Performance in Acrolein Oxidation. Journal of Molecular Catalysis A - Chemical, 185(1-2), 291-303. Retrieved from http://dx.doi.org/10.1016/S1381-1169(02)00128-0.

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Ovsitser, Olga1, Author              
Uchida, Yuji1, Author              
Mestl, Gerhard1, Author              
Weinberg, Gisela1, Author              
Blume, Andreas1, Author              
Jäger, Joachim1, Author              
Dieterle, Martin1, Author              
Hibst, Hartmut, Author
Schlögl, Robert1, Author              
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1Inorganic Chemistry, Fritz Haber Institute, Max Planck Society, ou_24023              

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Free keywords: molybdenum, vanadium, tungsten mixed oxide catalyst, acrolein selective oxidation, Mo5O14-type structure, structure-activity relation, activation 8:Mixed V/W/Mo oxides for selective oxidation
 Abstract: The activation of a Mo9V3W1.2Ox catalyst was investigated in the partial oxidation of acrolein as function of reaction temperature and atmosphere. The activity and selectivity to acrylic acid considerably increased during activation in the acrolein oxidation reaction comparable to the recently reported activation after thermal pretreatment in inert gas. The activation during the catalytic acrolein oxidation, however, proceeds at about 200 K lower temperatures as compared to the inert gas pretreatment. The initial nanocrystalline catalyst structure changed during operation in the acrolein oxidation, as shown by X-ray diffraction (XRD), scanning electron microscopy (SEM), transition electron microscopy and energy dispersive X-ray (EDX) analysis. A (MoVW)5O14-type mixed oxide was found to be the main crystalline phase in the active and selective catalysts. Hence, this (MoVW)5O14 phase crystallizes already during catalysis at the low acrolein oxidation reaction temperatures. The evolution of the catalytic performance is directly related to this low temperature formation of the (MoVW)5O14 phase. It is suggested that this (MoVW)5O14 phase has to be present in a detected, specific ordering state which is vital for optimum selective oxidation properties. In addition, other minority phases were identified by transmission electron microscopy (TEM) in the operating catalyst. The so-called bundle-type, and a new corona-type texture was detected, which show ordering in only one or two dimensions, respectively. These disordered structures are also relevant candidates for active catalyst phases as they are detected during the activation period of the MoVW mixed oxide.

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Language(s): eng - English
 Dates: 2002-07-08
 Publication Status: Published in print
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 Rev. Type: Peer
 Identifiers: eDoc: 1757
URI: http://dx.doi.org/10.1016/S1381-1169(02)00128-0
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Title: Journal of Molecular Catalysis A - Chemical
Source Genre: Journal
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Pages: - Volume / Issue: 185 (1-2) Sequence Number: - Start / End Page: 291 - 303 Identifier: ISSN: 1381-1169