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Properties of Pure and Sulfided NiMoO4 and CoMoO4 Catalysts: Tpr, Xanes and Time-Resolved XRD Studdzs

Published online by Cambridge University Press:  10 February 2011

S. Chaturvedi ,
J. A. Rodriguez ,
J. C. Hanson ,
A. Albornoz  and
J. L. Brito
S. Chaturvedi
Affiliation:
Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973, USA
J. A. Rodriguez*
Affiliation:
Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973, USA
J. C. Hanson
Affiliation:
Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973, USA
A. Albornoz
Affiliation:
Centro de Quimica, IVIC, Caracas 1020-A, Venezuela
J. L. Brito*
Affiliation:
Centro de Quimica, IVIC, Caracas 1020-A, Venezuela
*
(1)Authors to whom correspondence should be addressed
(1)Authors to whom correspondence should be addressed
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Abstract

X-ray absorption near-edge spectroscopy (XANES) was used to characterize the structural and electronic properties of a series of cobalt- and nickel-molybdate catalysts (AMoO4.nH20, α-AMoO4, β-AMoO4; A= Co or Ni). The results of XANES indicate that the Co and Ni atoms are in octahedral sites in all these compounds, while the coordination of Mo varies from octahedral in the a-phases to tetrahedral in the β-phases and hydrate. Time-resolved x-ray diffraction shows a direct transformation of the hydrates into the β-AMoO4 compounds (following a kinetics of first order) at temperatures between 200 and 350 °C. This is facilitated by the similarities that the AMoO4.nH20 and β-AMoO4 compounds have in their structural and electronic properties. The molybdates react with H 2 at temperatures between 400 and 600 °C, forming gaseous water and oxides in which the oxidation state of Co and Ni remains +2 while that of Mo is reduced to +5 or +4. After exposing α-NiMoO4 and P-NiMoO4 to H2S, both metals get sulfided and a NiMoSx phase is formed. For the β phase of NiMoO4 the sulfidation of Mo is more extensive than for the a phase, making the former a better precursor for catalysts of hydrodesulfurization reactions.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 497: Symposium Z – Recent Advances in Catalytic Materials , 1997 , 41
Copyright
Copyright © Materials Research Society 1998

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References

REFERENCES

1. Mazzocchia, C., Aboumrad, C., Diagne, C., Tempesti, E., Herrmann, J.M. and Thomas, G., Catal. Lett. 10, p. 181 (1991).Google Scholar
2. Brito, J.L., Barbosa, A.L., Albornoz, A., Severino, F. and Laine, J., Catal. Lett. 26, p. 329 (1994).Google Scholar
3. Brito, J.L. and Barbosa, A.L., J. Catal., 171, p. 467 (1997).Google Scholar
4. Proceedings of the 8th International Coference on X-ray Absorption Fine Structure (XAFSVIII), Physica B, 208&209 (1995).Google Scholar
5. Chen, J.G., Surf. Sci. Reports, 30, p. 1 (1997).Google Scholar
6. Thomas, J.M. and Thomas, W.J., The Principles and Practices of Heterogeneous Catalysis (VHC: New York, 1997).Google Scholar
7. Bare, S.R., Mitchell, G.E., Maj, J.J., Vrieland, G.E. and Gland, J.L., J. Phys. Chem. 97, p. 6048 (1993).Google Scholar
8. Norby, P., Christensen, A.N., and Hanson, J.C., Studies in Surf. Sci. Catal. 84, p. 179 (1994).Google Scholar
9. Nordlund-Christensen, A., Norby, P. and Hanson, J.C., J. Solid State Chem. 114, p. 556 (1995).Google Scholar
10. Norby, P. and Hanson, J.C., Catal. Today, submitted.Google Scholar
11. Rodriguez, J.A., Chaturvedi, S., Hanson, J.C., Albornoz, A. and Brito, J.L., to be published.Google Scholar
12. Brito, J.L., Laine, J. and Pratt, K.C., J. Mater. Sci. 24, p. 425 (1989).Google Scholar
13. Chaturvedi, S., Rodriguez, J.A. and Brito, J.L., to be published.Google Scholar