Epoxidation of styrene using carbon nanotubes-supported cobalt catalysts

Cobalt supported on carbon nanotubes (Co/CNTs) was developed as a novel cost-effective catalyst by impregnating CNTs in metallic precursor solution. The structures of the Co/CNTs catalysts were extensively characterized, and the presence of nanometer-sized Co particles was confirmed. The activity of Co/CNTs catalysts were examined for the epoxidation of styrene with tert-butyl hydroperoxide (TBHP) as the oxidant. The results showed that the catalytic behavior of Co/CNTs catalysts was closely correlated with the nature of oxidants, the structure of supports, and the polarity of the solvents. Compared with hydrogen peroxide, TBHP was a better oxidant for the epoxidation of styrene with the Co/CNTs catalyst, due to the lower dissociation energy. The favorable catalytic performance was obtained in acetonitrile solvent. The oxygen species with a radical nature activated by TBHP on the Co(II) site was proposed for the epoxidation reaction. This study also demonstrated that Co/CNTs catalysts were stable and could be reused without significant loss of activity.