Sol–gel palladium composites: effect of the thermal treatment on the catalytic activity

Composites of silica doped with palladium were prepared by a sol–gel method. The materials were characterized by powder X-ray diffraction, nitrogen adsorption and scanning electronic microscopy. A catalytic activity of the gels in the oxidation of limonene with dioxygen, in acetic acid solutions was investigated. The XRD patterns for the sample treated at 500 and 900 °C in air showed the presence of a PdO phase dispersed in the amorphous matrix of the silica. These samples had surface areas between (249 ± 12) and (420 ± 23) m2 g−1 with a mesoporosity contribution, and showed an activity in the formation of carveyl acetate. No palladium leaching was observed with allows catalyst recovery and reuse.