Rhenium modification on NiMo/Al2O3 catalyst and effects on the hydrodesulfurization reaction route selectivity of 4,6-dimethyldibenzothiophene

A series of Re modified NiMo/Al 2 O 3 hydrodesulfurization (HDS) catalysts with different contents of Re 2 O 7 were successfully synthesized by stepwise impregnation method and co-impregnation method respectively. The effects of Re modification and impregnation methods on the physical-chemical properties of the prepared catalysts were determined by the characterization techniques such as XRD, N 2 physical adsorption-desorption, NH 3 -TPD, Py-FTIR and HRTEM. Finally, the effects of the Re modification and the impregnation methods on the catalytic activity and the HDS reaction route selectivity were evaluated using 4,6-dimethyldibenzothiophene (4,6-DMDBT) as a probe. The results show that the crystal morphologies and pore structures of the synthesized catalysts varied with the contents of Re 2 O 7 and the impregnation methods and the amounts of acid sites can be modulated by the incorporation of Re 2 O 7 and the impregnation methods. Moreover, Re modification was conducive to the formation of the “type II” Ni-Mo-S active phase by changing the morphology of the Ni promoted MoS 2 slabs. The HDS evaluation of 4,6-DMDBT results show that Re modification can effectively improve the 4,6-DMDBT conversions, DDS route selectivity and even 3,3′-dimethylcyclohexanebenzene (3,3′-DMCHB) selectivity in varying degrees, and compared with that of co-impregnation method, the Re modification by stepwise impregnation method exhibited a more prominent effect. In general, 1 wt% Re 2 O 7 content was the most favorable to the HDS reaction since excessive Re 2 O 7 content has very little promoting effect.