Advertisement

Journal of thermal analysis

, Volume 41, Issue 2–3, pp 387–404 | Cite as

The non-isothermal decomposition of cobalt acetate tetrahydrate

A kinetic and thermodynamic study
  • M. A. Mohamed
  • S. A. Halawy
  • M. M. Ebrahim
Solid State Decompositions

Abstract

The non-isothermal decomposition of cobalt acetate tetrahydrate was studied up to 500°C by means of TG, DTG, DTA and DSC techniques in different atmospheres of N2, H2 and in air. The complete course of the decomposition is described on the basis of six thermal events. Two intermediate compounds (i.e. acetyl cobalt acetate and cobalt acetate hydroxide) were found to participate in the decomposition reaction.

IR spectroscopy, mass spectrometry and X-ray diffraction analysis were used to identify the solid products of calcination at different temperatures and in different atmospheres. CoO was identified as the final solid product in N2, and Co3O4 was produced in air. A hydrogen atmosphere, on the other hand, produces cobalt metal. Scanning electron microscopy was used to investigate the solid decomposition products at different stages of the reaction. Identification of the volatile gaseous products (in nitrogen and in oxygen) was performed using gas chromatography. The main products were: acetone, acetic acid, CO2 and acetaldehyde. The proportions of these products varied with the decomposition temperature and the prevailing atmosphere.

Kinetic parameters (e.g.E and lnA) together with thermodynamic functions (e.g. °H, C p and °S) were calculated for the different decomposition steps.

Keywords

cobalt acetate tetrahydrate IR kinetics MS non-isothermal decomposition thermodynamic study TG-DTG-DTA-DSC X-ray 

Zusammenfassung

In verschiedenen Atmosphären aus N2, H2 und in Luft wurde mittels TG, DTG, DTA und DSC bis zu 500°C die nichtisotherme Zersetzung von Kobaltacetat-Tetrahydrat untersucht. Der gesamte Umsetzungsprozeß wird auf der Grundlage von sechs thermischen Ereignissen beschrieben. Man fand, daß zwei Zwischenprodukte (Acetylkobaltacetat und Kobalt-acetathydroxid) an den Zersetzungsreaktionen beteiligt sind.

Die Bestimmung der Feststoffprodukte der kalzinierung bei verschiedenen Temperaturen und in verschiedenen Atmosphären erfolgte mittels IR-Spektroskopie, Massenspektrometrie und Röntgendiffraktion. In Stickstoff entsteht als festes Endprodukt CoO, in Luft hingegen Co3O4. In Wasserstoffatmosphäre kommt es jedoch zur Bildung von metallischem Kobalt. Mittels Scanning-Elektronenmikroskopie wurden die festen Zersetzungsprodukte zu verschiedenen Reaktionsstadien untersucht. Die Bestimmung flüchtiger gasförmiger Produkte (in Stickstoff und in Sauerstoff) erfolgte mittels Gaschromatographie. Die Hauptprodukte waren: Aceton, Essigsärue, CO2 und Acetaldehyd, deren relative Menge von der Zersetzungstemperatur und der vorherrschenden Temperatur abhängt.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    M. E. Brown, D. Dollimore and A. K. Galwey, Reactions in the Solid State (Comprehensive Chemical Kinetics, vol. 22), C. H. Bamford and C. F. H. Tipper (Eds), Elsevier, Amsterdam 1980.Google Scholar
  2. 2.
    D. L. Trimm, Design of Industrial Catalysts, Chemical Engineering Monograph II, Elsevier, Amsterdam 1980.Google Scholar
  3. 3.
    A. K. Galwey, S. G. McKee, T. R. B. Mitchell, M. A. Mohamed, M. E. Brown and A. F. Bean, Reactivity of Solids, 6 (1988) 203.Google Scholar
  4. 4.
    A. K. Galwey and M. A. Mohamed, Solid State Ionics, 42 (1990) 135.CrossRefGoogle Scholar
  5. 5.
    A. M. Gadalla and H. Fu Yu, Thermochim. Acta, 164 (1990) 21.CrossRefGoogle Scholar
  6. 6.
    J. Leicester and M. J. Redman, J. Appl. Chem., 12 (1962) 357.CrossRefGoogle Scholar
  7. 7.
    A. G. Galwey, S. G. McKee, T. R. B. Mitchell, M. E. Brown and A. F. Bean, Reactivity of Solids, 6 (1988) 173.CrossRefGoogle Scholar
  8. 8.
    R. Leibold and F. Huber, J. Thermal Anal., 18 (1980) 493.CrossRefGoogle Scholar
  9. 9.
    M. A. Mohamed, S. A. Halawy and M. M. Ibrahim, Submitted for publication.Google Scholar
  10. 10.
    S. A. A. Mansour, G. A. M. Hussein and M. I. Zaki, Reactivity of Solids, 8 (1990) 197.CrossRefGoogle Scholar
  11. 11.
    P. Baraldi, Spectrochim. Acta 38A (1982) 51.Google Scholar
  12. 12.
    Comprehensive Inorg. Chem. vol. 3, J. C. Bailar, H. J. Emeleus, R. Nyholm and A. F. Trotman-Dickenson (Eds), Pergamon Press, Oxford 1975.Google Scholar
  13. 13.
    R. C. Weast (Ed.), Handbook of Chemistry and Physics (62nd edn), CRC Press, Florida, 1982.Google Scholar
  14. 14.
    H. E. Kissenger, Anal. Chem., 29 (1957) 1702.CrossRefGoogle Scholar
  15. 15.
    M. A. Mohamed and S. A. Halawy, J. Thermal Anal., 41 (1994) 147.Google Scholar
  16. 16.
    S. F. Dyke, A. J. Floyed, M. Sainsbury and R. S. Theobald, Organic Spectroscopy-An Introduction (2nd edn), Longman, London 1978.Google Scholar
  17. 17.
    J. R. Ferraro, Low Frequency Vibration of Inorganic and Coordination Compounds, Plenum Press, New York 1971.Google Scholar
  18. 18.
    K. Nakamoto, Infrared Spectra of Inorganic and Coordination Compounds, J. Wiley and Sons, London 1963.Google Scholar
  19. 19.
    R. L. Pecsok, L. Shields, T. Cairns and T. G. McWilliam, Modern Methods of Chemical Analysis, 2nd edn, J. Wiley and Sons, London 1976.Google Scholar
  20. 20.
    N. T. McDevitt and W. L. Baun, Spectrochim. Acta, 20 (1964) 799.CrossRefGoogle Scholar
  21. 21.
    R. A. Nyquist and R. O. Kogal, Infrared Spectra of Inorganic Compounds, Academic Press, New York 1971, p. 219.Google Scholar
  22. 22.
    A. K. Galwey, M. A. Mohamed and D. S. Cromie, Reactivity of Solids, 1 (1986) 235.CrossRefGoogle Scholar
  23. 23.
    M. A. Mohamed, S. A. Halawy and M. M. Ebrahim, J. Anal. and Appl. Pyrolysis, in press.Google Scholar

Copyright information

© Wiley Heyden Ltd, Chichester and Akadémiai Kiadó 1994

Authors and Affiliations

  • M. A. Mohamed
    • 1
  • S. A. Halawy
    • 1
  • M. M. Ebrahim
    • 1
  1. 1.Department of Chemistry, Faculty of ScienceQenaEgypt

Personalised recommendations