Cyclohexane Oxidation Catalyzed by Au/MxOyAl2O3 Using Molecular Oxygen

Alumina was modified by doping with metal oxide and then used as the support for depositing gold by an impregnation-ammonia washing method to obtain Au/MxOy/Al2O3 (M=Co, Zr and Ce) catalysts. These samples were characterized by inductively coupled plasma-atomic emission spectrometry (ICP-AES), transmission electron microscope (TEM) and X-ray diffraction (XRD). The effects of Co3O4 content, metal oxide and mixed metal oxides on the catalytic activity for the selective oxidation of cyclohexane to cyclohexanone and cyclohexanol using molecular oxygen as oxidant were studied. The results showed that better catalytic performance was obtained over Au/MxOy/Al2O3 catalysts compared with over Au/Al2O3 catalysts. 9.69% conversion of cyclohexane and 93.31% selectivity to cyclohexanone, cyclohexanol and cyclohexyl hydroperoxide, with 1.02 ratio of cyclohexanone to cyclohexanol were obtained over the Au/MxOy/Al2O3 catalyst at 150 degrees C, 1.5 MPa for 3 h. Moreover, according to the recycling test, the catalyst could be reused four times without remarkable loss of activity.