Preparation of cyclonic Co3O4/Au/mesoporous SiO2 catalysts with core–shell structure for solvent-free oxidation of benzyl alcohol

Abstract

• A core–shell catalyst was prepared by cyclonic Co 3 O 4 as core and m-SiO 2 as shell for selective oxidation of benzyl alcohol. • 58% conversion and 82% selectivity were obtained together with the excellent reusability and stability. • A plausible oxidation reaction mechanism over SiO@Co 3 O 4 /Au@m-SiO 2 catalysts was tentatively proposed. As one of the ideal catalysts, noble metal materials can realize the conversion from benzyl alcohol to benzaldehyde. However, in previous reports, the loss of surface noble metal is one of the important reasons for the decrease in reaction performance. Here, a simple method was reported for stepwise fabrication of SiO 2 @Co 3 O 4 /Au@m-SiO 2 catalysts with core–shell structure. On the one hand, the core–shell structure provided abundant reaction sites for the oxidation of benzyl alcohol to benzaldehyde. On the other hand, the outer layer of m-SiO 2 effectively prevents the loss of Au nanoparticles. In this process, we studied the effects of multiple factors on the target reaction by controlling a single variable. The experimental results show that under the optimal conditions (the catalyst dosage, reaction temperature, reaction time and O 2 flow rate are 40 mg, 160 °C, 6 h, 60 ml/min, respectively), the conversion rate of the target reaction reaches 58% and the selectivity is as high as 82%. In the end, a mechanism was put forward to illustrate the underlying reaction pathway in benzyl alcohol oxidation.