Silver supported on hierarchically porous SiO2 and Co3O4 monoliths: Efficient heterogeneous catalyst for oxidation of cyclohexene

•Silver nanoparticles (10–30 nm) supported on monolithic SiO2 and Co3O4 have been prepared.•Monolithic Ag/SiO2 and Ag/Co3O4 have been used as recyclable heterogeneous catalysts for oxidation of cyclohexene.•Cyclohexene oxide was obtained as major product with cyclohexenone as the other product.•Plausible mechanisms have been proposed.

This study describes silver (Ag) nanoparticles supported on hierarchically porous SiO2 and Co3O4 monoliths and the use of these materials as heterogeneous catalysts for the oxidation of cyclohexene. Structural characterization of these materials was carried out by various techniques including scanning electron microscopy (SEM), N2 adsorption, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Characterization results revealed that Ag nanoparticles were incorporated into hierarchically porous SiO2 and Co3O4 without significantly affecting the structures of the supports. The oxidation of cyclohexene was investigated for hierarchically porous Ag/SiO2 and Ag/Co3O4 monoliths and powdered forms of the catalysts using H2O2 as oxidant. Detailed parameters including the effect of temperature, oxidant, catalyst loading, and substrate to oxidant ratio were thoroughly studied. The catalyst was found to be stable and could be reused several times without affecting its catalytic activity under the optimized reaction conditions.

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