Abstract

CALDERON, C.; REBOLLAR, M.; VALENZUELA, M. A.  and  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.

Keywords : Catalysts; palladium; mixed oxides; catalytic activity; deactivation.

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