Presulfurized\nHydrotreating Catalysts Prepared from\nTetrathiotungstate- Intercalated NiZnAl Layered Double Hydroxides

Zn was introduced into the sheets of WS<sub>4</sub><sup>2–</sup>-intercalated NiAl layered double hydroxides (LDHs),\nfollowed by\ncalcination under N<sub>2</sub> to prepare a series of presulfurized\nNiZnWAl hydrotreating (HT) catalysts. The influences of calcination\ntemperature and Ni/Zn ratio on the properties, hydrodesulfurization\n(HDS) activity for dibenzothiophene (DBT), and hydrodearomatization\n(HDA) activity for tetralin (THN) of the catalysts were investigated.\nThe incorporation of Zn led to the formation of ZnS on the surface\nand reduced the thermal stability of the LDHs. During the decomposition\nof LDHs, WS<sub>3</sub> and NiWS phases were formed successively,\nwhich are respectively related to HDA and HDS. Both WS<sub>3</sub> and NiWS decreased as the calcination temperature increased, due\nto the deep decomposition and the aggregation of metal sulfides. The\ncatalyst calcined at 300 °C shows the highest HDS and HDA activities.\nZn-containing catalysts exhibited much higher HDS activity but lower\nHDA activity compared to the catalyst without Zn. The rate constants <i>k</i><sub>HDS</sub> and <i>k</i><sub>HDA</sub> of\nthe catalyst with a Ni/Zn ratio of 0.2/1.8 were, respectively, 2.14\ntimes higher and 1.97 times lower than those of the catalyst without\nZn. For Zn-containing LDHs, the decomposition of interlayer WS<sub>4</sub><sup>2–</sup> was accelerated, leading to a decrease\nin WS<sub>3</sub>. Moreover, ZnS on the surface could enhance spillover\nhydrogen (H<sub>so</sub>) to form coordinately unsaturated sites (CUS)\nand further induces highly unsaturated CUS to depress the HYD activity.\nThis work might uncover a novel and convenient way to tune the HDS\nand HDA activities of LDH-based presulfurized HT catalysts by introducing\nZn, which is promising for deep HDS and controllable HDA of diesel\nfractions.