Effect of preparation methods on the hydrocracking performance of NiMo/Al2O3 catalysts

In this work, NiMo catalysts with various contents of MoOwere prepared through incipient wetness impregnation by a two-step method(NM-x A) and one-pot method(NM-xB). The catalysts were then characterized by XRD, XPS, NH-TPD, H-TPR, HR-TEM, and N2 adsorption–desorption technologies.The performance of the NiMo/AlOcatalysts was investigated by hydrocracking low-temperature coal tar. When the MoOcontent was 15 wt%, the interaction between Ni species and AlOon the NM-15 B catalyst was stronger than that on the NM-15 A catalyst, resulting in the poor performance of the former.When the MoOcontent was 20 wt%, MoOagglomerated on the surface of the NM-20 A catalyst, leading to decreased number of active sites and specific surface area and reduced catalytic performance. The increase in the number of MoSstack layers strengthened the interaction between Ni and Mo species of the NM-20 B catalyst and consequently improved its catalytic performance. When the MoOcontent reached 25 wt%, the active metals agglomerated on the surface of the NiMo catalysts, thereby directly decreasing the number of active sites. In conclusion, the two-step method is suitable for preparing catalysts with large pore diameter and low MoOcontent loading, and the one-pot method is more appropriate for preparing catalysts with large specific surface area and high MoOcontent. Moreover, the NMx A catalysts had larger average pore diameter than the NM-xB catalysts and exhibited improved desulfurization performance.