Solvent-free aerobic oxidation of benzyl alcohol over palladium catalysts supported on MnO x prepared using an adsorption method

Pd nanoparticles supported on MnO x (Pd/MnO x -ads) have been synthesized via the adsorption method and characterized using X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy techniques. The Pd nanoparticles with an average of 1.8 nm were highly dispersed on MnO x and Pd2+ ions were partially reduced to Pd0. Pd/MnO x -ads exhibited high activity and selectivity to benzaldehyde for the aerobic oxidation of benzyl alcohol without any solvent, compared with Pd/Mn3O4, Pd/CeO2 and Pd/Fe3O4 catalysts. Moreover, Pd/MnO x -ads showed remarkably higher activity than the catalysts prepared by adsorption-reduction and co-precipitation methods. The catalyst can be reused several times without obvious loss of its activity.