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采用浸渍法制备了一组NiO/γ-Al_2O_3样品,经550℃焙烧24小时,由UV漫反射光谱测定结果表明,当镍含量低于它在γ-Al_2O_3表面上的分散阈值(0.09g NiO/100m~2)时,镍处在氧的四面体和八面体两种配位中,以“表面镍尖晶石”的形式存在,当镍的含量超过此阈值时,同时出现NIO的特征谱带,以这些镰含量不同的NiO/γ-Al_2O_3样品再浸渍上钼,制备了几组含镍一定量而MoO_3载量不同的样品(450℃,24小时),应用X射线衍射,X射线光电子能谱以及UV漫反射光谱等方法进行研究。结果表明:在MoO_3—NiO/γ-Al_2O_3体系中,助催化剂NiO会提高MoO_3在γ-Al_2O_3表面的分散量,单层上处在八面体配位的镍或剩余的晶相NiO都能与MoO_3相互作用,并有助于MoO_3在γ-Al_2O_3表面分散,MoO_3在γ-Al_2O_3表面的最大分散量随NiO的含量的增加而增加。
A series of NiO / γ-Al_2O_3 samples were prepared by impregnation method and calcined at 550 ℃ for 24 hours. The results of UV diffuse reflectance spectroscopy showed that when the nickel content is lower than its dispersion threshold on the γ-Al_2O_3 surface (0.09g NiO / 100m ~ 2), nickel is in the form of “surface nickel spinel” in the coordination of tetrahedral and octahedral oxygen. When the nickel content exceeds this threshold value, the characteristic band of NIO appears at the same time The NiO / γ-Al 2 O 3 samples with different contents of these sickles were further impregnated with molybdenum to prepare a series of samples containing a certain amount of nickel and different MoO 3 loadings (450 ° C. for 24 hours). X-ray diffraction, X-ray photoelectron energy Spectroscopy and UV diffuse reflectance spectroscopy. The results showed that NiO promoted the dispersion of MoO_3 on the surface of γ-Al_2O_3 in the MoO_3-NiO / γ-Al_2O_3 system, while the octahedral NiO or NiO in the monolayer was comparable to that of MoO_3 And help the dispersion of MoO_3 on the surface of γ-Al_2O_3. The maximum dispersion of MoO_3 on the surface of γ-Al_2O_3 increases with the increase of NiO content.