Molybdenum oxide based partial oxidation catalyst: 1. Thermally induced oxygen deficiency, elemental and structural heterogeneity and the relation to catalytic performance

Mestl, Gerhard; Linsmeier, Ch.; Gottschall, Reiner; Dieterle, Martin; Herein, Daniel; Jäger, Joachim; Uchida, Yuji; Schlögl, Robert

doi:10.1016/s1381-1169(00)00340-x

Cited by 98 publications

(103 citation statements)

References 48 publications

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“…In early papers dealing with MoVO system for various applications, the presence or not of a [46]. Therefore, we shall assume that, as confirmed by LRS, θ- One of the main questions to answer is the formation of solid solutions in the metastable θ-phase, which is known to be stabilized by several cations to a given extent [45].…”

Section: Discussionmentioning

confidence: 97%

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Oxidation of ethane to ethylene and acetic acid by MoVNbO catalysts

et al. 2005

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Section: Discussionmentioning

confidence: 97%

“…It was reoxidation at 300°C, the initial mean valence state of V is not recovered. This may be due to the fact that Mo came onto the surface during reduction, the result being that some V specie are hidden and not reoxidized [46]. This trend is less marked in the presence of Nb.…”

Section: Discussionmentioning

confidence: 98%

Oxidation of ethane to ethylene and acetic acid by MoVNbO catalysts

et al. 2005

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“…The stabilisation effect of W and of the smaller particles compared to the crystallised samples inhibit a faster deactivation which is supported by the literature. 9,43 For spray-dried samples with W contents y 4 2 the phase composition seems to be stable against phase transformation under the investigated conditions. ACR with a concentration of 5 vol% in the reaction gas seems to have only negligible effects on the phase transformations.…”

Section: Post-mortem Characterisationmentioning

confidence: 91%

“…Mo 5 O 14 and MoO 3 seem to be stable against the reduction process. This can be explained by the stabilisation of thermodynamically metastable phases by tungsten 9 46 The re-oxidation of the reduced crystalline samples of both hydrochemical preparation methods in air again results in XRD patterns with crystalline structures. But a reconstruction of the hexagonal (V,Mo)O 3 structure type found before reduction fails.…”

Section: Reductive Conditionsmentioning

confidence: 98%

“…These results are not shown, because these are well known features of the catalysts, especially for the spray-dried samples. 9,51 The reactions are combined in the arrows and the phase transition area with the common stoichiometry (VMoW)O z . For the arrows a decomposition and a partially reconstructive transition of phases is observed.…”

Section: Models For Bulk and Reactionmentioning

confidence: 99%

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Heterogeneously catalysed partial oxidation of acrolein to acrylic acid—structure, function and dynamics of the V–Mo–W mixed oxides

Kampe

Giebeler

Samuelis

et al. 2007

Phys. Chem. Chem. Phys.

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The major objective of this research project was to reach a microscopic understanding of the structure, function and dynamics of V-Mo-(W) mixed oxides for the partial oxidation of acrolein to acrylic acid. Different model catalysts (from binary and ternary vanadium molybdenum oxides up to quaternary oxides with additional tungsten) were prepared via a solid state preparation route and hydrochemical preparation of precursors by spray-drying or crystallisation with subsequent calcination. The phase composition was investigated ex situ by XRD and HR-TEM. Solid state prepared samples are characterised by crystalline phases associated to suitable phase diagrams. Samples prepared from crystallised and spray-dried precursors show crystalline phases which are not part of the phase diagram. Amorphous or nanocrystalline structures are only found in tungsten doped samples. The kinetics of the partial oxidation as well as the catalysts' structure have been studied in situ by XAS, XRD, temperature programmed reaction and reduction as well as by a transient isotopic tracing technique (SSITKA). The reduction and re-oxidation kinetics of the bulk phase have been evaluated by XAS. A direct influence not only of the catalysts' composition but also of the preparation route is shown. Altogether correlations are drawn between structure, oxygen dynamics and the catalytic performance in terms of activity, selectivity and long-term stability. A model for the solid state behaviour under reaction conditions has been developed. Furthermore, isotope exchange experiments provided a closer image of the mechanism of the selective acrolein oxidation. Based on the in situ characterisation in combination with micro kinetic modelling a detailed reaction model which describes the oxygen exchange and the processes at the catalyst more precisely is discussed.

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Inorganic Chemistry Goes Protein Size: A Mo368 Nano-Hedgehog Initiating Nanochemistry by Symmetry Breaking

et al. 2002

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Molybdän‐Monster: Die Herstellung eines gewaltigen Molybdän‐Clusters wird beschrieben, wobei große Untereinheiten jeweils unterschiedliche lokale Symmetrien aufweisen (die Farben im Bild repräsentieren die kleineren Molybdat‐Fragmente). Verknüpft werden diese Molybdat‐Fragmente durch einen „Split‐and‐Link“‐Prozess auf vielfältige Arten, wobei geringfügige Änderungen in den Randbedingungen, insbesondere die das Wachstum kontrollierenden Redox‐Einflüsse, aber auch die H+‐Konzentration einen entscheidenden Einfluss auf den Prozess haben.

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Molybdenum oxide based partial oxidation catalyst: 1. Thermally induced oxygen deficiency, elemental and structural heterogeneity and the relation to catalytic performance

Cited by 98 publications

References 48 publications

Oxidation of ethane to ethylene and acetic acid by MoVNbO catalysts

Oxidation of ethane to ethylene and acetic acid by MoVNbO catalysts

Heterogeneously catalysed partial oxidation of acrolein to acrylic acid—structure, function and dynamics of the V–Mo–W mixed oxides

Inorganic Chemistry Goes Protein Size: A Mo368 Nano-Hedgehog Initiating Nanochemistry by Symmetry Breaking

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