The Low Temperature Solvent-Free Aerobic Oxidation of Cyclohexene to Cyclohexane Diol over Highly Active Au/Graphite and Au/Graphene Catalysts

The selectivity and activity of gold-catalysts supported on graphite and graphene have been compared in the oxidation of cyclohexene. These catalysts were prepared via impregnation and sol immobilisation methods, and tested using solventless and radical initiator-free reaction conditions. The selectivity of these catalysts has been directed towards cyclohexene epoxide using WO3 s a co-catalyst and further to cyclohexane diol by the addition of water, achieving a maximum selectivity of 17%to the diol. The sol immobilisation catalysts were more reproducible and far more active, however, selectivity towards the diol was lower than for the impregnation catalyst. The results suggest that formation of cyclohexane diol through solventless oxidation of cyclohexene is limited by a number of factors, such as the formation of an allylic hydroperoxyl species as well as the amount of in situ generated water.