Effect of High Pressure Sulfidation on the Structure of Sulfide Sites of Hydrotreatment Catalysts

The effect of high-pressure sulfidation on (Co)Mo/Al₂O₃ catalysts was studied by means of IR spectroscopy of adsorbed CO and thiophene hydrodesulfurization (HDS). A new IR cell, called CellEx, was designed in order to characterize catalysts sulfided in situ under H₂S/H₂ flow with pressure varying from 0.1 up to 4.0 MPa. On Mo/Al₂O₃, high sulfidation pressure changes neither the HDS rate nor the MoS₂ site concentration. Conversely on CoMo catalyst, sulfidation under high pressure leads to a marked increase of the thiophene HDS activity and of the Co-promoted site concentration as well as to some changes in the local structure of CoMoS sites. Graphical Abstract Study of CoMo catalyst, in the new IR cell, CellEX that allows in situ sulfidation under high-pressure, shows that sulfidation pressure increases HDS activity in parallel to the CoMoS concentration. [graphic removed]