Mesoporous silica as supports for Pd-catalyzed H2O2 direct synthesis: Effect of the textural properties of the support on the activity and selectivity

Pd-based catalysts supported on commercial silica, SBA-15 and MCM-41 were tested for the direct synthesis of hydrogen peroxide under very mild conditions of temperature and pressure and outside the explosion range. Silica and SBA-15 impart good catalytic activity, selectivity, mechanical stability and reusability. Best results were obtained with SBA-15 samples that show higher productivity than plain silica. Further catalytic tests were performed at higher pressures, still outside the explosive region. Even under these reaction conditions, the SBA-15 catalysts are the most selective. Characterization data indicate a close correlation between the textural properties of the support and the catalytic activity of the examined samples. The mean Pd particle size observed on the SBA-15 is a good compromise between a high metal dispersion necessary for high catalytic activity and the presence of less energetic sites, on which O2 can chemisorb without dissociation.