Comparasion of Different Catalysts on Phenol Hydroxylation

Fe2O3,heteropoly salt and Fe/ZrO2 exhibited high catalytic activity toward phenol hydroxylation using H2 O2 as oxidant.A rapid hydroxylation of phenol was observed after an induction period in the hydroxylation of phenol catalyzed by Fe2 O3;however,a slow hydroxylation of phenol was observed and the induction period disappeared in the same system catalyzed by heteropoly salt or Fe/ZrO2.The results suggest that,first,an induction period in hydroxylation of phenol is related to the formation of active species Fe3+and Fe2+ from Fe2O3;and second,the slow hydroxylation is related to the surface catalysis reaction on heteropoly salt or Fe/ZrO2,leading to the disappearance of the induction period.