SBA-15 as Support for Ni–MoS₂ HDS Catalysts Derived from Sulfur-containing Molybdenum and Nickel Complexes in the Reaction of HDS of DBT: An All Sulfide Route

Abstract

MoS₂ HDS catalysts promoted with Ni supported on SBA-15 were synthesized from sulfur containing Mo (ammonium thiomolybdate, ATM, and tetramethylammonium thiomolybdate, TMATM) and a Ni complex (Nickel diethylthiocarbamate, NiDETC). The catalysts have been characterized by X-ray diffraction (XRD), N₂-physisorption and High-resolution transmission electron microscopy (HRTEM). The catalytic performance in the hydrodesulfurization (HDS) reaction of dibenzothiophene (DBT) was examined at T = 623 K and P _H2 = 3.4 Mpa. In comparison with the impregnation mode, the nature of the employed thiomolybdate complex shows a stronger influence on the MoS₂ morphology and consequently on the HDS activity of DBT. A similar high HDS activity to a commercial NiMo/γ–Al₂O₃ catalyst despite the pronounced stacking number is shown for a Ni–MoS₂/SBA-15 catalyst derived from ATM. The catalysts derived from TMATM showed lower HDS activities compared to the catalysts obtained from ATM precursors due to probably the presence of closed shell structures (nano-onions) of MoS₂ which offer significantly smaller amount of HDS active sites (edge sites). Moreover, the HYD/DDS ratios are interestingly higher with respect to the HYD/DDS ratio of the commercial NiMo/γ–Al₂O₃ catalyst which could be ascribed to the generation of multilayered MoS₂ active phase.

Graphical Abstract

Nickel promoted molybdenum sulfide catalysts supported on mesoporous SBA-15 were prepared by an all sulfide route using Mo and Ni thiosalts. Similar high catalytic activity to a NiMo/γ–Al₂O₃ catalyst at high Mo loading is observed for Ni–MoS₂/SBA-15 catalysts derived from ammonium thiomolybdate despite a pronounced stacking of MoS₂ slabs. The catalysts prepared with tetramethylammonium thiomolybdate show lower HDS activities probably due to the generation of nano-onions composed of bent MoS₂ with a low crystalline perfection. The enhancement of the Ni content by post-impregnation leads to the formation of segregated Ni₃S₂ particles, which can cover the surface of the Ni–Mo–S phase resulting in a decrease of the HDS activity. The multilayered nature of the Ni–MoS₂ phase may be responsible for the higher HYD/DDS ratios (0.79–1.01).