Solvent-free aerobic oxidation of alcohols catalyzed by an efficient and recyclable palladium heterogeneous catalyst

A simple alumina-supported palladium catalyst prepared by an adsorption method is highly efficient and recyclable in the solvent-free oxidation of alcohols with molecular oxygen. The adsorption method results in high dispersion of palladium probably as mononuclear or oligonuclear species on alumina surface. These palladium species are transformed to small Pd nanoparticles (ca. 5 nm), which are probably the true active species, during the course of alcohol oxidation.