High loading of short WS₂ slabs inside SBA-15: Promotion with nickel and performance in hydrodesulfurization and hydrogenation

Layered nanoslabs of a WS₂ phase with a well-defined hexagonal crystalline structure, average slab length of 3.6 nm, and stacking number of 3. 2 were inserted into the nanotubular channels of SBA-15, an ordered pure silica material (surface area of 800 m²/g, uniform mesopore diameter of 6.5 nm) at loadings up to 60 wt.%. Sonication of a slurry containing SBA-15 in a W(CO)₆-sulfur-diphenylmethane solution yielded an amorphous WS ₂ phase inside the mesopores. By sulfidation with 1.5% dimethyldisulfide in toluene under a hydrogen flow at 593 K and 5.4 MPa, the amorphous phase was transformed into hexagonal crystalline WS₂ nanoslabs (as shown by XRD, HRTEM, and selected area electron diffraction (SAED)). The WS₂ nanoslabs were distributed exclusively inside the mesopores in a uniform manner (HRTEM, quantitative microanalysis), without blocking the pores (N₂-sorption), and were oriented with their edge planes toward the support surface. This study constitutes the first report of such a combination of high loading of a well-defined crystalline catalytic phase into the nanotubular channels of mesoporous silica without blocking them. The first well-resolved HRTEM images of the well-defined crystalline catalytic phase (WS₂) inside the SBA-15 nanotubes are presented. A Ni component was introduced into the WS₂/SBA-15 composite by impregnation from an aqueous solution of nickel acetate. It increased the catalytic activity up to a Ni/W ratio of 0.4. In the hydrodesulfurization (HDS) of dibenzothiophene and the hydrogenation (HYD) of toluene, the activity of the optimized Ni-W-S/SBA-15 catalyst was 1.4 and 7.3 times higher, respectively, than that of a sulfided commercial Co-Mo/Al₂O₃. This finding illustrates the excellent potential of high loading Ni-W-S/SBA-15 catalysts for deep hydrotreatment of petroleum feedstocks.