Spillover hydrogen mobility during Co–Mo catalyzed HDS in industrial-like conditions

The work concerns the spillover hydrogen (Hso) mobility between Co9S8 and MoS2 and the corresponding synergetic effects in gas–oil hydrodesulfurization (HDS), when a solid material separates the partners, either as a powder or a monolith surface. The influences of the distance (0–10 mm) between Co9S8 and MoS2 and the nature of the separator (γ-Al2O3, SiO2, carbon, MgSiO3 and two silica–aluminas) on the synergism were studied. A correlation exists between the value of the isoelectric point (IEP) of the separator surface and the enhancement of HDS activity. Inferring that the synergetic effect is due to hydrogen spillover, this shows that the IEP is an important parameter controlling spillover. To our knowledge, this is the first time the IEP of surfaces has been shown to have a direct effect on the spillover of hydrogen. The other results confirm that the remote control model is able to explain the synergism detected in this study.