Chuangchuang Yang

TiO₂-Al₂O₃ supports with different incorporation methods of titania were synthesized via three methods: impregnation (TA-I), co-precipitation (TA-CP), and co-precipitation–hydrothermal treatment (TA-HT). And the NiMoP catalysts prepared on the corresponding supports were evaluated for hydrodesulfurization (HDS) reactions. The results demonstrated that the Ti atoms in TA-I are attached to alumina through hydroxyl groups, while the Ti atoms in TA-CP and TA-HT can be dispersed in the alumina skeleton. Variations in the incorporation modes of TiO₂ affect the support properties, consequently influencing the nature of the active metal on the supports. The Ti atoms dispersed in the Al₂O₃ skeleton allow an increase in the basic hydroxyl groups. Meanwhile, TiO₂ in TA-CP and TA-HT can absorb hydrogen molecules and be partially reduced. Furthermore, metal species supported on the TA-CP and TA-HT are more easily reduced and better dispersed. For the NiMoP catalysts prepared with TA-CP and TA-HT, the Ti element promotes the sulfidation degree of Mo, besides shortening the average (Ni)MoS₂ slab. The catalysts prepared with TA-CP exhibited superior activity for 4,6-DMDBT hydrodesulfurization. This can be ascribed not only to the relatively high sulfidation degree of Mo and proportion of the NiMoS active phase but also to the well-dispersed (Ni)MoS₂ slabs. Moreover, the Ti⁴⁺ ions dispersed in the Al₂O₃ skeleton can be partially reduced to act as electron donors, enhancing the metallic character of the S layers in MoS₂, which facilitates the improvement of the hydrogenation desulfurization activity.

In this present work, a new kind of sulfurized hydrodesulfurization catalyst was synthesized via the hydrothermal treatment of MoS₂, NiCO₃·2Ni(OH)₂·4H₂O, and Al₂O₃ precursors, followed by annealing under a H₂ atmosphere, which does not require a sulfurization process compared to traditional preparation methods. The influence of the annealing temperature and the type of Al₂O₃ precursor on the interactions between MoS₂ and Al₂O₃ were studied using X-ray fluorescence spectroscopy, X-ray diffraction, N₂ adsorption–desorption, Raman spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The results indicated an increase in the number of stacked layers of the MoS₂ catalyst, accompanied by a decrease in the degree of decoration of Ni atoms onto MoS₂ nanoslabs, as a result of the strengthened MoS₂–Al₂O₃ interaction. Subsequently, the efficiency of hydrodesulfurization (HDS) was evaluated using dibenzothiophene as a representative reactant, while establishing a correlation between the structure of the catalyst and its performance. The catalysts, using pseudo-boehmite as the precursor and calcined at 500 °C, synthesized by calcining pseudo-boehmite as the precursor for Al₂O₃ at a temperature of 500 °C and possessing suitable metal–support interactions, exhibited a reduced number of MoS₂ stacking layers and lateral dimensions, along with an optimal decoration degree of Ni atoms, thereby resulting in the highest level of HDS activity.

Hydrodesulfurization (HDS) is an important process for the production of clean fuel oil, and the development of a new environmentally friendly, low-cost sulfided catalyst is key research in hydrogenation technology. Herein, commercial bulk MoS₂ and NiCO₃·2NiOH₂·4H₂O were first hydrothermally treated and then calcined in a H₂ or N₂ atmosphere to obtain Ni-MoS₂ HDS catalysts with different structures. Mechanisms of hydrothermal treatment and calcination on Ni-MoS₂ catalyst structures were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy (XPS). The catalytic performance of Ni-MoS₂ catalysts was evaluated by the HDS reaction of dibenzothiophene (DBT) on a fixed bed reactor, and the structure-activity relationship between the structures of the Ni-MoS₂ catalyst and the HDS of DBT was discussed. The results showed that the lateral size, the number of stacked layers, and the S/Mo atomic ratio of MoS₂ in the catalyst decreased and then increased with the increase of the hydrothermal treatment temperature, reaching the minimum at the hydrothermal treatment temperature of 150 °C, i.e., the lateral size of MoS₂ in the catalyst was 20-36 nm, the number of stacked layers of MoS₂ was 5.4, and the S/Mo ratio in the catalyst was 1.80. In addition, the effects of different calcination temperatures and calcination atmospheres on the catalyst structures were investigated at the optimum hydrothermal treatment temperature. The Ni-Mo-S and Ni_xS_y ratios of the catalysts increased and then decreased with the increasing calcination temperature under a H₂ atmosphere, reaching a maximum at a calcination temperature of 400 °C. Therefore, DBT exhibited the best HDS activity over the H-NiMo-150-400 catalyst, and the desulfurization rate of DBT reached 94.7% at a reaction temperature of 320 °C.