Characterization and HDS activity of sulfided Co[sbnd]Mo[sbnd]W/SBA-16 catalysts: Effects of P addition and Mo/(Mo + W) ratio

Abstract

Two series of SBA-16-supported CoMoW ternary sulfide catalysts with atomic ratio r=Mo/(Mo+W) ranging from 0.3 to 0.7 were prepared by the simultaneous impregnation of SBA-16andphosphated-SBA-16 substrates with metal precursors. The samples were characterized by a variety of techniques (chemical analysis, N2 physisorption, SEM, XRD, DRS UV–vis, TPR, TPD-NH3, Raman spectroscopy, HRTEM, XPS and coke burning). The catalytic performance was evaluated in the hydrodesulphurization (HDS) of dibenzothiophene (DBT), carried out in a batch reactor at 350°Cand3.1 MPaof total H2 pressure. The maximum activity at the same atomic ratio r=0.4 was observed for the catalysts supported on SBA-16 modified with phosphorous (r=0.4(P)). HRTEM evidenced that this was because different MoS2 crystalline structures were formed: the P-free sample prepared with Mo/(Mo+W) atomic ratio of 0.6 (r=0.6) exhibited the MoS2-2Hcrystalline structure whereas the P-containing samples prepared with Mo/(Mo+W) atomic ratio of 0.4 (r=0.4(P)) exhibited the interplanar distance corresponding to (003) planes of MoS2-3R crystalline structure. Additionally, the best activity of the r=0.4(P) sulfide catalyst was linked with the enhancement of the WS2 species surface exposure accompanied with a larger sulfidation degree of W species (from XPS).