Effect of stacking of MoS2 slabs on catalytic performance of supported CoMo-catalysts in hydrodesulfurization of dibenzothiophene

Hexagonal mesoporous materials with wormhole framework structures, having Si/Ti molar ratios of 80, 40 and 20 (Ti-HMS), were used as supports of sulfided-CoMo HDS catalysts. The catalysts were characterized by N-2 adsorption-desorption (S-BET), Raman spectroscopy and High-resolution transmission electron microscopy (HRTEM). The catalysts were tested in the reaction of hydrodesulfurization (HDS) of dibenzothiophene (DBT). The Ti-incorporation into the HMS framework have a beneficial effect in the formation of irregular Mo particles with terminal bonds (Mo = O). The most active catalysts showed the highest amount of irregular Mo particles in their oxide state, as deduced from the highest (Mo = O-T)/(Mo-O-Mo) Raman band intensities ratio. The common explanation for the greater activity of catalysts having larger amounts of irregular Mo particles are that those species could be good precursors of irregular stacking of MoS2 slabs, with the molybdenum atoms electronically less saturated. Probably, in this type of sites the adsorption of the reactant molecules will be easier. The presence of the Ti ions has a strong effect on the dispersion of the stacking layers of the MoS2 particles, evidenced by HRTEM results.