Effect of stacking of MoS_2 slabs on catalytic performance of supported CoMo-catalysts in hydrodesulfurization of dibenzothiophene

摘要

Hexagonal mesoporous silica (HMS) with wormhole framework structures, having Si/Ti molar ratios of 80, 40 and 20 (Ti(x)-HMS, x=80, 40 and 20), were used as supports of sulfided-CoMo hydrodesulfurization catalysts (CoMo/Ti(x)-HMS). A strong decrease was observed in the specific area—the pore diameter of the sulfided Ti-free sample in comparison with the Ti-containing samples. It can be noted that the Ti-incorporation into the HMS framework favors the preservation of the structural properties of the supports upon deposition and sulfidation of the active phases. The presence of Ti in the HMS material has a strong effect on the formation of irregular molybdenum particles with terminal bonds (Mo=O). The irregular molybdenum particles with terminal bonds species could be good precursors of the irregular stacking of MoS_2 slabs, with the molybdenum atoms electronically less saturated. In this type of site the adsorption of the reactant molecules would be expected to be easier. Furthermore, it is observed that the effect of the Ti-concentration is not linear (Fig. 1).