Pd catalysts supported on MnCeO_x mixed oxides and their catalytic application in solvent-free aerobic oxidation of benzyl alcohol: Support composition and structure sensitivity

Both crystalline and amorphous MnCeO_x supports were synthesized by co-precipitation and redox precipitation methods, respectively. Pd was subsequently deposited by an easy microwave-assisted polyol reduction procedure, leading to the formation of highly dispersed Pd nanoclusters. MnCeO_x supports were remarkably enhanced in both catalytic activity and selectivity in the aerobic oxidation of benzyl alcohol, compared with pure MnO_x and CeO₂. The highest qTOFs (quasi-turnover frequencies) were achieved over Pd/7Mn3Ce-C (15,235 h^-1) and Pd/7Mn3Ce-A (14,438 h ^-1), and the activity could be maintained over five consecutive reaction runs. Pd acts as a single active component, and the synergetic interactions among Pd, MnO_x, and CeO₂ result in enhanced catalytic activity. Good accessibility of the Pd active sites and a high surface concentration of Pd⁰ contribute to the high initial reaction rate over crystalline MnCeO_x-supported Pd catalyst. Amorphous MnCeO _x-supported Pd catalyst exhibits enhanced catalyst stability due to mutual promotion between redox properties and oxygen mobility.