Mesoporous CeO2-MnOx binary oxides with different Mn/Ce molar ratios were prepared by hydrothermal synthesis and characterized by scanning electron microscopy(SEM),N2 sorption,X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS) and H2 temperature-programmed reduction(H2-TPR).The characterization results indicated that the CeO2-MnOx catalysts exhibited flower-like microspheres with high specific surface areas,and partial Mn cations could be incorporated into CeO2 lattice to form solid solution.The CeO2-MnOx catalysts showed better catalytic activity for CO oxidation than that prepared by the coprecipitation method.Furthermore,the CeO2-MnOx catalyst with Mn/Ce molar ratio of 1 in the synthesis gel(Ce-Mn-1) exhibited the best catalytic activity,over which the conversion of CO could achieve 90% at 135 oC.This was ascribed to presence of more Mn species with higher oxidation state on the surface and the better reducibility over the Ce-Mn-1 catalyst than other CeO2-MnOx catalysts.
Selective oxidation of saturated hydrocarbons with molecular oxygen has been of great interest in catalysis, and the development of highly efficient catalysts for this process is a crucial challenge. A new kind of heterogeneous catalyst, cobalt-doped carbon nitride polymer(g-C_3N_4),was harnessed for the selective oxidation of cyclohexane. X-ray diffraction, Fourier transform infrared spectra and high resolution transmission electron microscope revealed that Co species were highly dispersed in g-C_3N_4 matrix and the characteristic structure of polymeric g-C_3N_4 can be retained after Co-doping, although Co-doping caused the incomplete polymerization to some extent. Ultraviolet-visible, Raman and X-ray photoelectron spectroscopy further proved the successful Co doping in g-C_3N_4 matrix as the form of Co(Ⅱ)-N bonds. For the selective oxidation of cyclohexane, Co-doping can markedly promote the catalytic performance of g-C_3N_4 catalyst due to the synergistic effect of Co species and gC_3N_4 hybrid. Furthermore, the content of Co largely affected the activity of Co-doped g-C_3N_4 catalysts, among which the catalyst with 9.0 wt%Co content exhibited the highest yield(9.0%) of cyclohexanone and cyclohexanol, as well as a high stability. Meanwhile, the reaction mechanism over Co-doped g-C_3N_4 catalysts was elaborated.
Yu FuWangcheng ZhanYanglong GuoYun GuoYunsong WangGuanzhong Lu
