Investigation of selectivity over HDS catalysts by in situ IR spectra of adsorbed CO and molecular simulation calculation

Two CoMo/Al ₂O ₃ catalysts with different supports(Al ₂O ₃-A and Al ₂O ₃-B) were prepared by pore-filling impregnation. Active phases of the sulfided CoMo/Al ₂O ₃ catalysts were identified and analyzed quantitatively by means of in situ FTIR spectrum of adsorbed CO. The charge distribution, adsorption energy and activation energies of hydrotreating reaction of thiophene and 1-hexene on the MoS ₂ surface before and after adding Co were calculated by molecular simulation, respectively. The results reveal that the increase of CoMoS phase on the catalyst surface improves the HDS/HYD selectivity. Compared with HYD site of 1-hexene, the electron accepting ability of thiophene HDS site can be improved significantly by the adding of Co support, which benefits to improve the adsorptions of thiophene on the surface over catalyst and decrease the activation energy barrier of HDS for thiophene. This fact also points out that the CoMoS phase is the active site of high HDS and HDS/HYD selectivity.