Producción Científica Profesorado

Effect of the particle size on the activity of MoOxCy catalysts for the isomerization of heptane



Villagómez Ibarra, José Roberto

2005

Effect of the particle size on the activity of MoOxCy catalysts for the isomerization of heptane L. O. Alemàn-Vàzquez, E. Torres-Garcia, J.R. Villagómez-Ibarra, and J.L. Cano-Dominguez. Catalysis Letters Vol. 100, Nos.3-4, April 2005


Abstract


Molybdenum trioxide samples having apparent particle sizes (APS) of 5 and 20 l.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 MoOxCy 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 l.m showed a maximum conversion around 70%, while for the catalyst with an APS of 5 l.m the maximum conversion was 34%. The lower activity of the 5 l.m MoOxCy 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.



Producto de Investigación




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