Direct Hydroxylation of Benzene to Phenol over Fe3O4 Supported on Nanoporous Carbon

Fe3O4/CMK-3 was prepared by impregnation and used as a catalyst for the direct hydroxylation of benzene to phenol with hydrogen peroxide. The iron species in the prepared catalyst was Fe3O4 because of the partial reduction of iron(III) to iron(I I) on the surface of CMK-3. The high catalytic activity of the catalyst arises from the formation of Fe3O4 on the surface of CMK-3 and the high selectivity for phenol is attributed to the consumption of excess hydroxyl radicals by CMK-3. The effect of temperature, reaction time, volume of H2O2, and amount of catalyst on the catalytic performance of the prepared catalyst were investigated. Under optimized conditions, the catalyst showed excellent catalytic performance for the hydroxylation of benzene to phenol and 18% benzene conversion was achieved with 92% selectivity for phenol and with a TOF value of 8.7 h(-1). The stability of catalyst was investigated by determining its activity after the fourth run and it was found to have decreased to 80% of the fresh catalyst's activity.