Effect of iron on Cu/SiO2 catalysts for the dehydrogenation of cyclohexanol to cyclohexanone

At the temperature range of 250–390°C, the addition of iron to Cu/SiO₂ catalyst increased the conversion and the selectivity of cyclohexanone. The iron incorporation into Cu/SiO₂ catalyst enhanced the reduction temperature of copper oxide, increased the dispersion of copper metal and decreased the selectivity of cyclohexene. Copper was enriched on the surface of the used metal catalyst compared to that in freshly calcined or reduced catalyst. Unlike Cu dispersed on bulk iron oxide, the Cu-Fe dispersed on silica showed negligible amount of phenol formation, thus keeping the selectivity of cyclohexanone very high even at high reaction temperatures. The Fe³⁺ ion in the reduced Cu/Fe/SiO₂ catalyst resulted in a significant resistance of the Cu particle to sintering and a decrease in the selectivity of phenol arisen from the magnetite.