Description of coordinatively unsaturated sites regeneration over MoS2-based HDS catalysts using 35S experiments combined with computer simulations

Franck Dumeignil (1, 2, 3) , Jean-Francois Paul (2) , Edouard Veilly (2) , Eika W. Qian (3) , Atsushi Ishihara (3) , Edmond Payen (1, 2) , Toshiaki Kabe (3)

1 LCL - Laboratoire de catalyse de Lille - UMR 8010
2 UCCS - Unité de Catalyse et Chimie du Solide - UMR 8181
3 TUAT - Department of Chemical Engineering, Tokyo University of Agriculture and Technology

By combining experimental results and computer simulations, we previously showed that the coordinatively unsaturated sites (CUS) formation over MoS2 is most likely to occur on the MoS2 metallic edge through the departure of an H2S molecule. In the present paper, we aimed at examining the H2S departure from MoS2 catalysts promoted with Co and Ni. The [35S]DBT HDS experiments results showed that over CoMoS/Al2O3 and NiMoS/Al2O3 catalysts, the activation energy of the H2S release reaction is essentially the same with respective values of 7.4 kcal.mol-1 and 7.9 kcal.mol-1. Considering the H2S departure activation energy in the case of the non-promoted MoS2 surface (10 ~ 12 kcal.mol-1), this result illustrates the synergetic effect between Mo and Co or Ni in terms of CUS regeneration easiness. Further, preliminary computer simulations results showed that for S atoms bridged between Co atoms, a mechanism implying H2S departure from the metallic edge cannot be reasonably envisaged. Moreover, on the sulfur edge the H2S release activation energy is too high (~ 13.5 kcal.mol-1) if we consider experimental results on CoMo/Al2O3 catalysts but not incompatible with the experimental value obtained over Co/Al2O3 catalysts (ca. 10 kcal.mol-1), which suggests that the mechanism on the promoted catalyst differs from that on the un-promoted one.

Mots clés: HDS; DBT; MoS2; CoMoS; NiMoS; activation energy; 35S tracer experiments; computer simulations; H2S liberation

Domaines: Catalyse

Franck Dumeignil, Jean-Francois Paul, Edouard Veilly, Eika W. Qian, Atsushi Ishihara, et al.. Description of coordinatively unsaturated sites regeneration over MoS2-based HDS catalysts using 35S experiments combined with computer simulations. Applied Catalysis A : General, 2005, 289(1), pp.51-58. ⟨hal-00098365⟩