Abstract:

Co-doped MCM-41 supported catalysts 5%ZnO/xCo-MCM-41 were prepared by impregnation method, and applied in the synthesis of isovaleric aldehyde from isoamyl alcohol with dioxygen. The samples were characterized via X-ray diffraction(XRD), fourier transform-infrared spectroscopy(FTIR), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), scanning electron microscopy(SEM), NH-3 temperature programmed desorption(NH-3-TPD), H-2 temperature programmed reduction(H-2-TPR) and N-2 adsorption-desorption. The effects of Co-doping amount on the structure and catalytic performance of molecular sieves were investigated. The results showed that the specific area and pore volume of samples decreased gradually with the increase of Co-doping amount, while median pore diameter first increased and then decreased. 5% ZnO/Co-MCM-41 molecular sieves still remained ordered hexagonal mesopore structure of MCM-41 and had high speci-fic surface area(989 m²/g), pore size(2.88 nm) and larger pore volume(0.88 cm³/g) when Co-doping amount was 0.05. The cobalt introduced into Co-MCM-41 existed mainly as single-site Co(Ⅱ) ions, which improved the effective dispersion of ZnO and moderately reduced the acidity of 5% ZnO/MCM-41 mole-cular sieves. At the same time, it improved the oxidation-reduction potential of 5% ZnO/MCM-41. Compared with 5%ZnO/MCM-41, The selectivity of isovaleric aldehyde increased 28.3% with 5% ZnO/0.05Co-MCM-41.

Key words: ZnO/Co-MCM-41 molecular sieve, Catalytic oxidation, Isovaleric aldehyde, Selectivity