2017 Volume 96 Issue 5 Pages 144-152
Titania coating of mesoporous silicas (MSs) with different pore size was performed several times under thoroughly dried circumstances. When the pore size was 3 nm, the pore-plugging took place by only one time coating. On the other hand, for the pore size of 7 nm, a uniform coating with titania layer could be achieved until three time coating, and for that of 10 nm, the uniform coating without pore-plugging was obtained even after five time coating. These observations could be explained by the difference in the curvature of the silica pore walls. From various analyses and characterization, it was found that the titania coating was uniform and that three time coating was needed to coat all the silica walls and then possible coating mechanism was proposed. The MSs coated with titania were applied as the support of Mo catalyst for hydrodesulfurization (HDS) of sulfur-containing aromatics. The effect of titania coating on the dibenzothiophene HDS was not significant, but positive increase in activity was observed for 4,6-dimethyldibenzothiophene HDS. This increase was due to the enhancement of hydrogenation ability, in agreement with the results from the naphthalene hydrogenation. Moreover, it was found the formation of three-dimensional pores is very useful to increase the HDS activity.
