Naphthalene and tetralin hydrocracking behaviors were investigated over NiMo and CoMo catalysts. The results showed that CoMo catalyst with high concentration of S-edges could hydrosaturate more naphthalene to tetralin but exhibit lower yield of high-value light aromatics (carbon numbers less than 10) than NiMo catalyst. NiMo catalyst with high concentration of Mo-edges also presented a higher selectivity to convert naphthalene to cylanes than CoMo catalyst. Subsequently, the naphthalene and LCO hydrocracking performances were also investigated over different catalysts systems. It showed that the naphthalene hydrocracking conversion and the yield of light aromatics for CoMo-AY/NiMo-AY grading catalysts were higher than NiMo-AY/CoMo-AY grading catalysts at same condition. A stepwise reaction principle was proposed to explain the high-efficiency of CoMo-AY/NiMo-AY grading catalysts. Finally, the LCO hydrocracking evaluation results confirmed that CoMo-AY/NiMo-AY catalysts grading system with low carbon deposition and high stability was more efficient to convert LCO to high-octane gasoline.
Dual-metal modifications on SBA-16 silica were implemented to modulate the acidities and the distribution and dispersion of active phases for NiMo catalysts. The results showed that the acidity of S-H groups in S-edge sites can be promoted by B acid and further facilitate the DDS selectivity. The NiMo/AT-7.5 catalyst exhibits the highest HDS efficiency of 97.5% due to its appropriate acidity, highest proportion of MoS2 phase and concentration of S-edge sites. The kinetic and thermodynamic analyses were applied to investigate the intrinsic HDS reactivity for various catalysts. The results confirmed the existence of synergistic effect in the DBT HDS reaction. The B acid sites can further increase the desulfurization route (DS) of THDBT to CHB. A higher dispersion degree of MoS2 could improve DBT HDS efficiency. A high total concentration of S-edge and Mo-edge will indicate a high HDS efficiency. The S-edge/Mo-edge ratio and kDDS/kHYD could be correlated.