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Catalysis Letters

, Volume 100, Issue 3–4, pp 219–226 | Cite as

Effect of the particle size on the activity of MoO x C y catalysts for the isomerization of heptane

  • L. O. Alemán-VázquezEmail author
  • E. Torres-García
  • J. R. Villagómez-Ibarra
  • J. L. Cano-Domínguez
Article

Molybdenum trioxide samples having apparent particle sizes (APS) of 5 and 20 μ.m were partially reduced under flow of a mixture of H2/n-heptane during 4 h. X-ray diffraction and Raman spectroscopy showed the typical structural transformation of MoO3 into MoO x C y and MoO2. These structural changes occur preferentially on the {0k0} planes. After the reduction treatment the resulting materials, having surface areas of 23 and 53 m2/g, were evaluated in the isomerization of n-heptane at 643 K and 18.5 bar. The catalyst with an APS of 20 μ.m showed a maximum conversion around 70%, while for the catalyst with an APS of 5 μ.m the maximum conversion was 34%. The lower activity of the 5 μ.m MoO x C y catalyst seems to be related to a faster rate of formation of oxygen vacancies and rearrangement of the lattice into a more stable and less active structure in the case of small-size particles, due to a higher concentration of terminal Mo=O bonds along the a- and b-axes, which facilitate the electrophilic attack by hydrogen on the (010) plane.

Keywords

molybdenum oxycarbide heptanes isomerization particle size Raman spectroscopy X-ray diffraction 

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Copyright information

© Springer Science+Business Media, Inc. 2005

Authors and Affiliations

  • L. O. Alemán-Vázquez
    • 1
    • 2
    Email author
  • E. Torres-García
    • 1
  • J. R. Villagómez-Ibarra
    • 2
  • J. L. Cano-Domínguez
    • 1
  1. 1.Instituto Mexicano del PetróleoPrograma de Tratamiento de Crudo MayaMéxicoMéxico
  2. 2.Centro de Investigaciones QuímicasUniversidad Autónoma del Estado de HidalgoPachucaMéxico

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