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当MoO_3含量低于单层分散容量时,MoO_3/γ-Al_2O_3喇曼谱图上两个最突出的峰是～950cm~(-1)的宽峰和876cm~(-1)的较尖锐峰。前者代表“二维聚铝酸”(其中的铝主要是八面体配位的),是加氢脱硫(HDS)等活性中心的前身;后者代表孤立的、四面体配位的钿物种,在加氢脱硫反应中没有活性。用定性和定量的方法系统研究了浸渍液的pH值、焙烧温度、时间、MoO_3总含量等因素对MoO_3/γ-Al_2O_3中两种钼物种相对含量的影响。探讨了在制备过程中减少这种四面体配位钼物种相对含量的方法。指出添加ZnO,使γ-Al_2O_3变成缺锌铝酸锌可以在一定程度上抑制此种非活性钼物种的生成,从而达到提高催化剂活性的目的。
When the content of MoO_3 is lower than the monolayer dispersion capacity, the two most prominent peaks in the Raman spectrum of MoO_3 / γ-Al_2O_3 are the broad peak of ~ 950cm -1 and the sharper peak of 876cm -1. The former represents “two-dimensional polyaluminum acid” (aluminum is mainly octahedral coordinated) and is the predecessor of active centers such as hydrodesulfurization (HDS); the latter represents the isolated tetrahedron coordination 钿 species, No activity in hydrodesulfurization reaction. The effects of pH value, calcination temperature, time and total content of MoO 3 on the relative content of Mo species in the MoO 3 / γ-Al 2 O 3 system were systematically studied by qualitative and quantitative methods. The method of reducing the relative content of this tetrahedral coordination molybdenum species in the preparation process was discussed. It is pointed out that the addition of ZnO and the transformation of γ-Al 2 O 3 into zinc-deficient zinc aluminate can restrain the formation of such non-reactive molybdenum species to a certain extent so as to improve the activity of the catalyst.