Pd-CeO2 nanorods catalyzed solvent free oxidation of benzyl alcohol derivatives to aldehydes

Selective oxidation of benzylic alcohols is a crucial reaction in organic syntheses because the products, such as aldehydes and ketones, play important roles in numerous industries. Noble metals have been proved to be able to effectively catalyze this reaction in relatively green conditions. In the present research, solvent-free aerobic oxidation of several benzylic alcohols catalyzed by palladium oxide supported on ceria nanorods (PdOx/CeO2-NR) is investigated. The Ceria nanorods (CeO2-NR) were prepared by a hydrothermal process, and calcination. Pd(NO3)2 was deposited on the CeO2-NR by a wet impregnation process at mild conditions and the resulting PdOx/CeO2-NR catalyst was prepared by calcination at 500 °C. The prepared material was fully characterized (XRD, SEM, BET, XPS). Solvent-free aerobic oxidations of benzyl alcohol derivatives were performed using this PdOx/CeO2-NR . The results of the reactions were studied by GC-MS. Presence of electron-donating groups on benzyl alcohol aromatic ring led to an increase in the conversion even if with a decrease in selectivity while substitution of electron-withdrawing groups resulted in drastic lowering of the catalytic activity. A mechanistic explanation will be presented.