Mössbauer Spectroscopy Studies of the State of Heterogeneous Catalysts during Catalysis

  • J. A. Dumesic
  • Yu. V. Maksimov
  • I. P. Suzdalev

Abstract

The magnetic state of a metallic catalyst for the ammonia synthesis and the electronic state of oxide catalysts for the propylene and methanol oxidations were investigated using Mössbauer spectroscopy during the respective catalytic reactions. The experiments were carried out in cells which served simultaneously as catalytic reactors and units for Mössbauer spectroscopy — “Mössbauer catalytic reactors.”

The metallic catalyst for the ammonia synthesis consisted of small iron particles (ca. 5 nm in size) supported on MgO. The superparamagnetic relaxation frequency for these particles was found to be sensitive to both hydrogen chemisorption on the particles and to treatments of the particles which were shown to change their catalytic properties. These results can be understood in terms of Néel’s phenomenological theory of magnetic-surface anisotropy; in addition, surface iron atoms with seven nearest neighbors seem to be particularly active for the ammonia synthesis.

For the soft oxidation of propylene and methanol, cobalt molybdate containing minor amounts of iron and nonstoichiometric iron molybdates were used as catalysts. In both cases, the iron initially entered the catalyst structure mainly in the trivalent state. During both catalytic processes, however, additional, partially reduced forms of iron were detected, and these forms disappeared upon termination of the reaction. These electronic states of iron can be treated in terms of vacancy models.

Keywords

Formaldehyde Anisotropy Cobalt Catalysis Propylene 

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References

  1. 1.
    Goldanskii, V. I., and Suzdalev, I. P., Proc. Conf. Appl. Mössbauer Effect, Tihany (Hungary), p. 269, 1969.Google Scholar
  2. 2.
    Hobson, M. C., Jr., Surface Membrane Sci. 5, 1 (1972).Google Scholar
  3. 3.
    Gager, H. M., and Hobson, M. C., Jr., Catal. Rev. 11, 117 (1975).CrossRefGoogle Scholar
  4. 4.
    Goldanskii, V. I., Maksimov, Yu. V., and Suzdalev, I. P., Proc. Fifth Inter. Conf. Mössbauer Spectroscopy, Cracow (Poland ), 1975.Google Scholar
  5. 5.
    Dumesic, J. A., and Topsøe, H., Adv. Catal., in press.Google Scholar
  6. 6.
    Khammouma, S., Ph.D. Dissertation, Stanford University, 1972.Google Scholar
  7. 7.
    Boudart, M., Delbouille, A., Dumesic, J. A., Khammouma, S., and Topsøe, H., J. Catal. 37, 486 (1975).CrossRefGoogle Scholar
  8. 8.
    Boudart, M., Robert A. Welch Foundation Conferences on Chemical Research. XIV. Solid State Chemistry, Milligan, W. O. (Ed.), Houston, Texas, p. 299, 1971.Google Scholar
  9. 9.
    Dumesic, J. A., Topsøe, H., Khammouma, S., and Boudart, M., J. Catal. 37, 503 (1975).CrossRefGoogle Scholar
  10. 10.
    Boudart, M., Dumesic, J. A., and Topsde, H., in The Physical Basis of Heterogeneous Catalysis, Jaffee, R. ( Ed. ), Gstaad (Switzerland), 1975.Google Scholar
  11. 11.
    Dumesic, J. A., Topsoe, H., and Boudart, M., J. Catal. 37, 513 (1975).CrossRefGoogle Scholar
  12. 12.
    Néel, L., Compt. Rend. Acad. Sci. 237, 1468 (1953).Google Scholar
  13. 13.
    Néel, L., J. Phys. Radium 15, 225 (1954).CrossRefGoogle Scholar
  14. 14.
    Van Hardeveld, R., and Hartog, F., Surface Sci. 15, 189 (1969).CrossRefGoogle Scholar
  15. 15.
    Maksimov, Yu. V., Suzdalev, I. P., Goldanskii, V. I., Krylov, O. V., Margolis, L. Ya., and Nechitailo, A. E., Chem. Phys. Letters 34, N1, 172 (1975).CrossRefGoogle Scholar
  16. 16.
    Maksimov, Yu. V., Suzdalev, I. P., Goldanskii, V. I., Matveev, A. I., Makarov, E. F., and Margolis, L. Ya., Dokl. Akad. Nauk USSR, to be published.Google Scholar
  17. 17.
    Sancier, K. M., Aoshime, A., and Wise, H., J. Catal. 34, 257 (1974).CrossRefGoogle Scholar
  18. 18.
    Bibin, V. N., and Popov, B. I., Kinet. Katal. (Russian) 10, 1326 (1969).Google Scholar
  19. 19.
    Plasova, L. M., Klefsova, R. F., Borisov, S. V., and Kefeli, L. M., Crystallography (Russian) 12, 939 (1967).Google Scholar
  20. 20.
    Pernicone, N., J. Less Common Metals 36, 289 (1974).CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 1976

Authors and Affiliations

  • J. A. Dumesic
    • 1
    • 2
    • 3
  • Yu. V. Maksimov
    • 1
    • 2
    • 4
  • I. P. Suzdalev
    • 1
    • 2
    • 4
  1. 1.Stanford UniversityStanfordUSA
  2. 2.Institute of Chemical PhysicsMoscowUSSR
  3. 3.Department of Chemical EngineeringUniversity of WisconsinMadisonUSA
  4. 4.Institute of Chemical PhysicsAcademy of Sciences of the Soviet UnionMoscowUSSR

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