摘要
用N_2物理吸附、紫外漫反射光谱和低温氧化学吸咐方法,考察了Mo/Al_2O_3中Mo物种在Al_2O_3上沉积情况和化学结构以及硫化后的变化。发现MoO_3含量低于10％时,Mo物种呈不饱和单分子层,以Mo[T]物种为主;大于10％后,逐渐出现多层沉积,Mo[O]物种增多。硫化后样品有扩孔现象发生,其程度与MoO_3含量成反比。低温氧化学吸附结果表明,Mo[T]物种易于形成不饱和配位的Mo离子(CUS),这种物种同γ-Al_2O_3的相互作用及它的还原性都与CUS的形成有一定关系。
The physical state and chemical structure of Mo species in Mo/ A12O3 catalyst as well as their change by sulfidation have been investigated by nitrogen physical adsorption, ultraviolet-diffuse reflectance spectra and low temperature oxygen chemisorption (LTOC). It is found that when MoO3 content is less than 10%, Mo species supported on A12O3 are in monolayer deposition and the Mo(T) species predominates; when MoO3 content is more than 10%,the polylayer deposition containing Mo(O) species takes place. After sulfidation there occurs expansion of pore on Mo/Al2O3. The degree of expansion is inversely proportional to MoO3 content. LTOC results show that moderate degree of reduction and the interaction between r-Al2O3 and Mo(T) species are favourable to the formation of coordinately unsaturated Mo ions.
