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Revista de la Sociedad Química de México
versión impresa ISSN 0583-7693
Resumen
CALDERON, C.; REBOLLAR, M.; VALENZUELA, M. A. y SALMONES, J.. Catalizadores de Pd soportados en óxidos mixtos Al-Mg: síntesis, caracterización y actividad. Rev. Soc. Quím. Méx [online]. 2001, vol.45, n.1, pp.06-12. ISSN 0583-7693.
Al-Mg mixed oxides supports with various compositions were synthezised by coprecipitation and sol-gel. The characterization was carried out by atomic absorption, thermal analysis (DTA/TGA), N2 physisorption, and X-ray diffraction (XRD). These solids, after calcined at 600 °C were used as supports of monometallic Pd (1 %) catalysts prepared by impregnation. The catalytic properties were evaluated in a flow micro-reactor at 500 °C and atmospheric pressure. The highest specific surface area values and the major homogeneity in pore size distribution were obtained with the sol-gel preparations compared with the coprecipitated. In spite of low calcination temperature, the main compounds detected by XRD were MgAl2O4 spinel, and free phases of MgO and Al2O3, depending of Al2O3 / MgO molar ratios. The highest conversion levels were obtained with solids showing spinel structure (more stable) having a low metal-support interaction. By this reason, monometallic Pd catalysts supported on coprecipitated solids (mainly with spinel structure) were more active than those supported on sol-gel. The selectivity to propylene in both series of catalysts varied in the range of 57 to 93 %, which it was explained as a function of the surface acidity. A major deactivation was observed with Pd catalysts supported on sol-gel mixed oxides.
Palabras llave : Catalysts; palladium; mixed oxides; catalytic activity; deactivation.