The effect of thermal treatment on the properties of sol–gel palladium–silica catalysts

Abstract This work intends to evaluate Pd-doped silica obtained by sol–gel method as a heterogeneous catalyst for the degradation of organic reactions. The wet gel obtained from a starting solution containing tetraethylorthosilicate and palladium chloride was dried at 110 °C to obtain the xerogel, and thermally treated at various temperatures. The structural and morphological changes were measured by powder X-ray diffraction, scanning electron microscopy, nitrogen adsorption, and thermal analysis. The composites heated at temperatures between 300 and 700 °C had surface areas between 404 and 341 m2 g−1 with mesoporosity contribution. These samples, specially Pd/SiO2 (300 °C), had activity for the total oxidation of chlorobenzene. Thermal treatment over 700 °C densified the samples with a decrease in specific area. As a result of these processes, the palladium species were entrapped inside the vitreous silica matrix decreasing the catalytic activity.