Highly dispersed copper species within SBA-15 introduced by the hydrophobic core of a surfactant micelle as a carrier and their enhanced catalytic activity for cyclohexane oxidation

Highly dispersed copper species were successfully coated onto the inner surface of the rodlike mesoporous SBA-15 silica by a newly developed strategy. The hydrophobic core of the surfactant micelle in the as-synthesized SBA-15 was effectively employed as a carrier for the hydrophobic precursors of copper acetyl acetonate (Cu(acac)₂) during hydrothermal treatment (HT) before surfactant removal, and the copper-derivated catalysis centers within SBA-15 were strategically generated on pyrolysis. Characterizations of the synthesized samples by a series of techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), electron paramagnetic resonance (EPR), temperature-programmed reduction (TPR), UV-vis, X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma atomic emission spectroscopy (ICP-AES) manifested that about 0.19-0.85 wt % copper was directly introduced and dispersed into the inner surface of the SBA-15 pore network. While there were few studies, if any, to utilize synthetic copper catalysts for the selective oxidation of cyclohexane oxidation, it was found that currently synthesized Cu-SBA-15 demonstrated very interesting catalytic properties for this industrially important reaction. Under the optimized reaction condition at an oxygen pressure of 1 MPa and a temperature of 120 °C for 7 h, the conversion of cyclohexane to the target products was higher than 11%; meanwhile, the total selectivity to cyclohexanol and cyclohexanone satisfactorily reached ca. 80%.