Templated Synthesis of Mesoporous Co<sub>3</sub>O<sub>4</sub> Nanostructures for the Liquid-Phase Aerobic Oxidation of Benzyl Alcohol to Benzaldehyde
Kai Li, Pei Yao, Ping Xiao, Zhiyan He, Sónia A. C. Carabineiro, Huiyu Jiang, Junjiang Zhu
Abstract
Mesoporous Co3O4 nanostructures, templated from different mesoporous silicas, SBA-3, SBA-5, and SBA-16, were used as catalysts for the liquid-phase selective oxidation of benzyl alcohol using molecular oxygen as the oxidant. The nanostructured Co3O4-16, templated from SBA-16, showed the best activity for the reaction, with 97.5% benzyl alcohol conversion and 100% benzaldehyde selectivity obtained after 3 h of reaction at 100 °C. This could be attributed to its large number of oxygen vacancies and low surface Co3+/Co2+ ratio that were beneficial to O2 activation, together with its three-dimensional nanostructure that facilitated the adsorption of benzyl alcohol, compared to Co3O4-3 and Co3O4-15. The material could be reused without losing activity if the organics adsorbed on the surface of the used sample were removed by calcination at 300 °C for 1 h. A mechanism for the reaction was proposed, considering that the activation of molecular oxygen was the rate-determining step of the reaction.