Fe-Supported SBA-16 Type Cagelike Mesoporous Silica with Enhanced Catalytic Activity for Direct Hydroxylation of Benzene to Phenol

In this work, an Fe-supported cagelike mesoporous silica type SBA-16 catalyst (Fe/SBA-16) was successfully synthesized using iron nitrate as the precursor through a simple impregnation method. Results of X-ray diffraction, N-2 adsorption-desorption, transmission electron microscopy, and elemental mapping analysis showed that the mesoporous structure of the support was retained during catalyst preparation and that iron nanoparticles were dispersed on the SBA-16 surface. Moreover, ultraviolet visible and X-ray photoelectron spectroscopic studies revealed that the iron(III) oxidation state was dominant in the Fe-supported cagelike mesoporous silica. It was found that the Fe/SBA-16 was an appropriate catalyst for the benzene hydroxylation to phenol using H2O2 as the oxidant. The effects on the catalytic performance of operating parameters such as the amount of H2O2, reaction temperature, reaction time, and catalyst dosage were investigated. Under the optimized conditions, 11.7% phenol yield and 96.4% selectivity to phenol were obtained; in addition, the catalyst could be recycled at least three times.