Synthesis of highly loaded and well dispersed CuO/SBA-15 via an ultrasonic post-grafting method and its application as a catalyst for the direct hydroxylation of benzene to phenol

•A novel ultrasonic post-grafting method has been developed.•A reusable CuO/SBA-15 catalyst with high copper loading and good dispersion has been synthesized and characterized.•Direct hydroxylation of benzene to phenol has been carried out with the CuO/SBA-15 catalyst.•The obtained catalyst exhibits high catalytic activity and recyclability.

A novel ultrasonic post-grafting method has been developed to obtain highly-loaded and well-dispersed CuO nanoclusters inside the channels of mesoporous silica (SBA-15). Trimethylchlorosilane (TMCS) and 3-aminopropyltriethoxysilane (APTES) were used as modification surfactants, and copper nitrate solution was used as the precursor. The samples were characterized by FT-IR, XRD, SAXRD, ICP-AES, BET, HRTEM, TPR and XPS, which illustrated that the CuO clusters were well-dispersed in very small sizes. The hydroxylation of benzene to phenol in a one-step liquid-phase process using CuO/SBA-15 as the catalyst was evaluated. High conversion (28%) and selectivity (95%) were achieved with a 13.4 wt.% copper grafted on SBA-15. Furthermore, the catalyst was shown to have the ability to be recycled up to five times without a significant loss of conversion or selectivity.

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