D. Solis1*, J. Ramírez♣ 2, R. Cuevas, R. Contreras2, T. Cortéz3, M. Aguilar4
1 Facultad de Química, UAEM, Paseo Tollocan y Paseo Colón s/n Toluca, 50000, México, *solis_casados@yahoo.com.mx
2 UNICAT, Departamento de Ingeniería Química, Facultad de Química, UNAM
3 ♣ Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas 152, México D.F. 07730. México
4 Instituto de Física, UNAM
]]> Recibido: 17 de marzo de 2006.
Abstract
CoMo catalysts were prepared using Al2O3-MgO-(X) hybrid supports, where X = K2O or Li2O. The textural, structural and acid-base properties of these materials were characterized by several techniques. The catalysts were preliminarily evaluated in the hydrodesulfurization (HDS), hydrogenation (HYD) and hydrocracking (HCK) model reactions. The aims of this work are to identify the effect of the addition of an alkaline oxide (either K2O or Li2O) to the Lewis acid sites in the CoMo/Al2O3-MgO formulation; and on the other hand, to establish a relationship between the acidity and the catalytic performance (hydrogenation function). The results obtained from the pyridine thermodesorption analysis and the n-butyl amine titration techniques show that the incorporation of an alkaline oxide to the CoMo/Al2O3-MgO formulation causes a slight decrease in the total number of acid sites (TNAS) with respect to Al2O3 and the Al2O3-MgO hybrid supports. Both the enhanced textural and structural stability of the CoMo/Al2O3-MgO-(X) catalytic formulations, which could be probably attributed to the incorporation of Li or K cations to the MgO framework, stabilizing it, can also be observed. As for the catalytic performance, the CoMo/Al2O3-MgO-(X) catalysts containing either Li2O or K2O, show a decrease in both the HYD and HYC conversions; however, the formulation containing Li2O shows the best catalytic behavior due to both the low n-octane yield and the low hydrocracking activity.
Keywords: Lithium; Potassium; Magnesia; Acid sites; Hydrodesulfurization; Hydrogenation.
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Acknowledgements
]]> The financial support given by the IMP (Instituto Mexicano del Petróleo) through the FIES 98-116-II program is amply acknowledged. The authors want to thank Dra. Ma. Elena Llanos for her help in the N2 physisorption measurements; and Engineer René Zarate Ramos for his valuable comments. D. Solis thanks CONACyT for the support given through the "Programa de Retención/Consolidación Institucional"; and the SIEA-UAEM for the support given through the 2349, 2368/UAEM and SEP-PROMEP 103.5/07/2572 Projects.
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