Presulfurized Hydrotreating Catalysts Prepared from Tetrathiotungstate- Intercalated NiZnAl Layered Double Hydroxides

Zn was introduced into the sheets of WS42–-intercalated NiAl layered double hydroxides (LDHs), followed by calcination under N2 to prepare a series of presulfurized NiZnWAl hydrotreating (HT) catalysts. The influences of calcination temperature and Ni/Zn ratio on the properties, hydrodesulfurization (HDS) activity for dibenzothiophene (DBT), and hydrodearomatization (HDA) activity for tetralin (THN) of the catalysts were investigated. The incorporation of Zn led to the formation of ZnS on the surface and reduced the thermal stability of the LDHs. During the decomposition of LDHs, WS3 and NiWS phases were formed successively, which are respectively related to HDA and HDS. Both WS3 and NiWS decreased as the calcination temperature increased, due to the deep decomposition and the aggregation of metal sulfides. The catalyst calcined at 300 °C shows the highest HDS and HDA activities. Zn-containing catalysts exhibited much higher HDS activity but lower HDA activity compared to the catalyst without Zn. The rate constants kHDS and kHDA of the catalyst with a Ni/Zn ratio of 0.2/1.8 were, respectively, 2.14 times higher and 1.97 times lower than those of the catalyst without Zn. For Zn-containing LDHs, the decomposition of interlayer WS42– was accelerated, leading to a decrease in WS3. Moreover, ZnS on the surface could enhance spillover hydrogen (Hso) to form coordinately unsaturated sites (CUS) and further induces highly unsaturated CUS to depress the HYD activity. This work might uncover a novel and convenient way to tune the HDS and HDA activities of LDH-based presulfurized HT catalysts by introducing Zn, which is promising for deep HDS and controllable HDA of diesel fractions.