The preparation of Fe/wood-based activated carbon catalyst for phenol hydroxylation from Fe2+ and Fe3+ precursors

A series of Fe/wood-based activated carbon catalysts with 0.89-6.94 wt% Fe loading were prepared using an impregnation-co-precipitation method, and the catalysts were characterized by inductively coupled plasma-atomic emission spectrometry, N-2 adsorption-desorption, X-ray diffraction, X-ray photoelectron spectroscopy, magnetic measurements, ultraviolet-visible diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy and high resolution transmission electron microscopy. The results indicated that iron oxide species including Fe2+ and Fe3+ forming the active sites were successfully loaded on woodbased activated carbon. With increasing concentration of iron ions in the preparation process, iron oxide species were saturated gradually on the support. These catalysts have been assessed for the hydroxylation of phenol to dihydroxybenzenes using H2O2 as oxidant. The results showed that the catalytic activity was improved with the increase in the Fe content. The active phase for phenol hydroxylation could be the cooperation of the two iron oxide species. Under the optimized conditions, the catalyst with an Fe content of 6.55 wt% gave a phenol conversion of 51.1% with 80.6% of selectivity to dihydroxybenzenes. Finally, the results of catalyst recycling illustrated that the catalyst could be reused with slight Fe leaching and slight loss of activity.