摘要
通过采用动态氧吸附法(DOC)和常压下噻吩加氢脱硫反应(HDS)研究了TiO_2对Mo-Co/γ-A(?)_2O_3系催化剂的助催化效应. 结表表明TiO_2的加入使催化剂的活性中心数目增加,内在活性提高.在没有Co存在时,TiO_2既不能增加MoO_3/γ-Al_2O_3的活性中心数目,也不能提高其催化活性.可见Ti-Co之间存在协同效应,即TiO_2的助催化效应只有在Co存在下才能表现出来.Ti-Co协同效应的结果可能使催化剂中形成更多的内在活性高的类型ⅡCo-Mo-S活性相.
The promotion effects of TiO2 upon Mo-Co/γ-A12O3 HDS catalyst were studied by Dynamic Oxygen Chemisorption Method and HDS test reaction of thiophene.It is shown that the activity of TiO2 containing catalyst increases through a maximum with the increase of TiO2 content ( or Ti/Mo ratio). It is of interest, to note that when the catalyst contains no Co, TiO2 does not show any effect towards MoO3/γ-Al2O3.
The results of DOC determination exhibit a parallel relation with the results of catalyst activity test. The adsorption amount of O2 as well as the active site number of Mo for TiO2 containing Mo-Co/γ-A12O3 catalyst are larger than those of Mo-Co/γ-A12O3. But TiO2 does not change the O2 adsorption amount of MoO3/γ-Al2O3 .Moreover, the HDS activity of catalyst increases linearly with the increase of O2 adsorption amount.
According to the results given above, it is suggested that the promotion effect of TiO2 upon the catalyst is realized through the coordinated action between TiO2 and CoO.Owing to the interaction of TiO2 with Al2O3,the reduction and sulfiding of MoO3 are enhanced,the formation of surface complex of CoO and A12O3 is inhibited. These results increases the, formation probability of Co-Mo-S ( II ) phase in the catalyst. Therefore both the active center number and the intrinsic activity of Mo-Co/γ-Al2O3 catalyst are increased.
出处
《分子催化》
EI
CAS
CSCD
1989年第3期204-210,共7页
Journal of Molecular Catalysis(China)
