Abstract: In this work, a series of Mg-Sn-W oxide powder catalysts with different tungsten oxide contents (0, 15 wt% and 30 wt%) were prepared and washcoated on cordierite honeycomb monoliths to produce monolithic catalysts, which were tested for the Baeyer-Villiger oxidation of cyclohexanone. The obtained monolithic catalysts, which combined the advantages of both homogeneous and heterogeneous catalysts, showed high catalytic efficiency and overcame the problems of product separation that occurred in the homogeneous catalytic process. SEM and EDX tests showed that the catalytic coating, with a thickness of approximately 20 μm, was compact and homogeneous, and an enlarged BET surface area was indicated by N₂ adsorption-desorption compared with the bare cordierite honeycomb. The chemical properties on the catalytic surface of the powder and monolithic catalysts were characterized by XPS, which indicated the tin and tungsten on the catalysts exhibited their full oxide states and presented mainly as stannate and tungstate, as confirmed by XRD and FTIR characterizations. Moreover, the catalytic activity test indicated that the tungsten content of the catalysts played an important role in catalytic efficiency and that monolithic catalysts were produced without obvious catalytic activity loss compared with the corresponding powders. (M)W30, which exhibited excellent mechanical stability and maintained high activity after recycling three times, was the optimal catalyst, showing a high selectivity that exceeded 86% and a conversion above 64%. Therefore, the structured Mg-Sn-W oxide catalysts have great potential for application in practical production.

Key words: Baeyer-Villiger oxidation, Monolith, Mg-Sn-W oxide catalysts, Synthesis, &epsilon, -Caprolactone

摘要： In this work, a series of Mg-Sn-W oxide powder catalysts with different tungsten oxide contents (0, 15 wt% and 30 wt%) were prepared and washcoated on cordierite honeycomb monoliths to produce monolithic catalysts, which were tested for the Baeyer-Villiger oxidation of cyclohexanone. The obtained monolithic catalysts, which combined the advantages of both homogeneous and heterogeneous catalysts, showed high catalytic efficiency and overcame the problems of product separation that occurred in the homogeneous catalytic process. SEM and EDX tests showed that the catalytic coating, with a thickness of approximately 20 μm, was compact and homogeneous, and an enlarged BET surface area was indicated by N₂ adsorption-desorption compared with the bare cordierite honeycomb. The chemical properties on the catalytic surface of the powder and monolithic catalysts were characterized by XPS, which indicated the tin and tungsten on the catalysts exhibited their full oxide states and presented mainly as stannate and tungstate, as confirmed by XRD and FTIR characterizations. Moreover, the catalytic activity test indicated that the tungsten content of the catalysts played an important role in catalytic efficiency and that monolithic catalysts were produced without obvious catalytic activity loss compared with the corresponding powders. (M)W30, which exhibited excellent mechanical stability and maintained high activity after recycling three times, was the optimal catalyst, showing a high selectivity that exceeded 86% and a conversion above 64%. Therefore, the structured Mg-Sn-W oxide catalysts have great potential for application in practical production.

关键词: Baeyer-Villiger oxidation, Monolith, Mg-Sn-W oxide catalysts, Synthesis, &epsilon, -Caprolactone