Topics in Catalysis

, Volume 15, Issue 2, pp 219–228

In situ analysis of metal-oxide systems used for selective oxidation catalysis: how essential is chemical complexity?

Authors

  • R. Schlögl
    • Department of Inorganic ChemistryFritz-Haber-Institut der Max-Planck-Gesellschaft
  • A. Knop-Gericke
    • Department of Inorganic ChemistryFritz-Haber-Institut der Max-Planck-Gesellschaft
  • M. Hävecker
    • Department of Inorganic ChemistryFritz-Haber-Institut der Max-Planck-Gesellschaft
  • U. Wild
    • Department of Inorganic ChemistryFritz-Haber-Institut der Max-Planck-Gesellschaft
  • D. Frickel
    • Department of Inorganic ChemistryFritz-Haber-Institut der Max-Planck-Gesellschaft
  • T. Ressler
    • Department of Inorganic ChemistryFritz-Haber-Institut der Max-Planck-Gesellschaft
  • R.E. Jentoft
    • Department of Inorganic ChemistryFritz-Haber-Institut der Max-Planck-Gesellschaft
  • J. Wienold
    • Department of Inorganic ChemistryFritz-Haber-Institut der Max-Planck-Gesellschaft
  • G. Mestl
    • Department of Inorganic ChemistryFritz-Haber-Institut der Max-Planck-Gesellschaft
  • A. Blume
    • Department of Inorganic ChemistryFritz-Haber-Institut der Max-Planck-Gesellschaft
  • O. Timpe
    • Department of Inorganic ChemistryFritz-Haber-Institut der Max-Planck-Gesellschaft
  • Y. Uchida
    • Department of Inorganic ChemistryFritz-Haber-Institut der Max-Planck-Gesellschaft
Article

DOI: 10.1023/A:1016696400146

Cite this article as:
Schlögl, R., Knop-Gericke, A., Hävecker, M. et al. Topics in Catalysis (2001) 15: 219. doi:10.1023/A:1016696400146

Abstract

The mode of operation of selective oxidation reactions is described by a series of chemical rules defining the catalyst and some reaction intermediates. In contrast to catalytic processes over metallic elements, little is known, however, about the atomistic details of selective oxidation. In particular, the participation of the subsurface region of the catalyst in the kinetically relevant elementary steps (Mars–van Krevelen mechanism) is not positively verified. Using in situ X-ray absorption techniques to study binary and ternary molybdenum oxides the present contribution shows that it is possible to tackle some of the problems in selective oxidation by direct experimental observation. The modification of the Mo–O local bonding interaction upon thermal reduction of MoO3to MoO3-xis illustrated. This was also found for mixed Mo–V oxides in which the chemical state of the vanadium seemed unaffected by the reaction but the surface Mo : V ratio varied substantially with the gas phase composition. It is further shown that the solid-state phase transformation between reduced and oxidised forms of molybdenum oxides occur so rapidly, that possibly relevant suboxide cannot be identified by ex situ phase analysis. Observation of the time-law of redox transformations showed that lattice oxygen is only available for selective oxidation if the associated solid-state transformation occurs in the kinetic regime of reaction control and not in that of diffusion control.

O K-edge NEXAFSV L-edge NEXAFSXPSin situ time-resolved Mo K-edge EXAFSMoO3ammonium heptamolybdate
Download to read the full article text

Copyright information

© Plenum Publishing Corporation 2001