SiO2 supported Ce–Co mixed oxide catalyzed selective allylic oxidation of cyclohexene

In this study, silica supported ceria, ceria–cobalt mixed oxide, silica supported ceria–cobalt mixed oxide, pure ceria, and cobalt oxide (CeO2/SiO2, CeO2–Co3O4 and CeO2–Co3O4/SiO2, CeO2, and Co3O4) catalysts were prepared and evaluated for selective oxidation of cyclohexene to allylic products (i.e., 2-cyclohexen-1-ol and 2-cyclohexen-1-one). The above catalysts were prepared through co-precipitation and deposition co-precipitation methods. Various physical characterization techniques namely XRD analysis, BET studies, Raman studies, FE-SEM analysis, XPS analysis, and NH3-TPD analysis were used to investigate the structure, morphology, surface area and the textural properties of the catalysts. The results have confirmed that the Co doped into the ceria and dispersed on silica leads to enhanced surface area, oxygen vacancies and the redox behavior of the catalyst. Among all these catalysts, the silica supported cobalt doped ceria catalyst CeO2–Co3O4/SiO2 showed superior catalytic activity towards cyclohexene oxidation reactions. Conversion of cyclohexene and selectivity for allylic products depend on various reaction parameters namely the reaction temperature, reaction time, amount of the catalyst, cyclohexene/oxidant ratios, and nature of the solvent.