Liquid phase hydroxylation of benzene to phenol over Cu/ZnO catalysts

Liquid phase hydroxylation of benzene to phenol using Cu/ZnO catalysts prepared by the polyol process was investigated in aqueous acetic acid (20/80, v/v). Gaseous oxygen and ascorbic acid were utilized as the oxidant and reducing agent, respectively. The results showed that there is an optimum copper content over zinc oxide support. Phenol was the sole product of the oxidation reaction. No other product in the liquid phase was detected by gas chromatography and mass spectroscopy. Cu/ZnO catalysts prepared by the polyol process were found to be highly effective catalysts for direct phenol synthesis in the liquid phase. A major disadvantage of this system was that Cu/ZnO catalysts suffered from dissolution in the reaction medium. Cu/ZnO catalysts prepared by the polyol reduction showed comparatively higher activities.