Effect of TiO 2 Coating on Morphology of Active Phase on Sulfided CoMo/Al 2 O 3 Hydrotreating Catalysts

A series of CoMo catalysts supported on various Al 2 O 3 supports added with TiO 2 were prepared to investigate the addition effect of TiO 2 on formation of an active phase on sulfided CoMo/Al 2 O 3 catalyst. The catalytic activity tests were carried out with hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene, hydrodenitrogenation (HDN) of acridine, and hydrodearomatization (HDA) of o -xylene, 1-methylnaphthalene (1-MN), and phenanthrene. A 20 wt % TiO 2 added CoMoAlTi20 catalyst showed the lowest hydrogenation activity in HDA of 1-MN and phenanthrene and highest HDS and HDN activities. The property of a support and/or the interaction between active metal and the support significantly affect the formation of active sites for HDS and HDA. The active sites for HDS on sulfided CoMo catalysts were different from those for HDA and/or hydrogenation. The addition of TiO 2 enhanced the reduction, the formation, and stacking number of CoMoS active slabs. The finding that desulfurization via the hydrogenation pathway (HYDS) activity increased while the HDA activity slightly decreased over TiO 2 coated catalysts reveals that the increased amounts of formed CoMoS overcome the increase of the stacking number of CoMoS active slabs.