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 m(2)/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 WS2 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 (N-2-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 nanombes 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. (C) 2002 Elsevier Science (USA), All rights reserved.