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

Both crystalline and amorphous MnCeOx 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. MnCeOx supports were remarkably enhanced in both catalytic activity and selectivity in the aerobic oxidation of benzyl alcohol, compared with pure MnOx 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, MnOx, and CeO2 result in enhanced catalytic activity. Good accessibility of the Pd active sites and a high surface concentration of Pd-0 contribute to the high initial reaction rate over crystalline MnCeOx-supported Pd catalyst. Amorphous MnCeOx-supported Pd catalyst exhibits enhanced catalyst stability due to mutual promotion between redox properties and oxygen mobility. (C) 2011 Elsevier Inc. All rights reserved.