Dual Effect of H₂S on Volcano Curves in Hydrotreating Sulfide Catalysis

Abstract

Résumé -Effet dual d'H 2 S sur les courbes en volcan en catalyse d'hydrotraitement -Les progrès récents des techniques de modélisation moléculaire quantique ont permis l'interprétation rationnelle des tendances périodiques observées en catalyse par les sulfures de métaux de transition. Les courbes en volcan obtenues de façon empirique peuvent être expliquées par des modélisations microcinétiques inté-grant des descripteurs chimiques judicieux calculés ab initio. Cette approche a été appliquée avec succès en catalyse d'hydrotraitement en utilisant l'énergie de liaison metal-soufre comme descripteur ab initio. L'objectif du présent travail était d'étendre cette approche en explorant les effets des conditions réaction-nelles (pression partielle en H 2 S) sur les courbes en volcan. Dans ce but, les images de microscopie électronique à transmission haute résolution (METHR) combinées à la modélisation moléculaire des morphologies et des surfaces présentes ont permis de fournir une évaluation du nombre de sites potentiellement actifs. Cette approche est illustrée dans le cas du sulfure de cobalt supporté et non supporté. Un modèle microcinétique amélioré permet d'interpréter l'effet dual de l'H 2 S observé en hydrogénation du toluène: effet inhibiteur pour les sulfures MoS 2 , Rh 2 S 3 , RuS 2 , NiMoS et effet promoteur pour les sulfures Cr 2 S 3 et Co 9 S 8 . Les résultats expérimentaux combinés à la modélisation cinétique montrent que la position du maximum de la courbe en volcan correspondant au catalyseur optimal le plus performant dépend des conditions du milieu réactionnel. Abstract -Dual Effect of H 2 S on Volcano Curves in Hydrotreating Sulfide Catalysis -Recent progresses achieved by quantum molecular modeling techniques enabled the rational interpretation of catalytic trends of series of transition metal sulfide catalysts. Empirical volcano curves can be explained by microkinetic models including chemical descriptors calculated at an ab initio level. This approach was successfully applied in the field

A Rational Comparison of the Optimal Promoter Edge Decoration of HDT NiMoS vs CoMoS Catalysts

“…Mixed Co(Ni)-Mo sites present at the M-edge exhibit intermediate sulfur-metal bond energy values comprised between non-promoted Mo-site and pure Co site. Recent microkinetic investigations of the toluene hydrogenation on various transition metal sulfide catalysts have shown that a volcano curve correlates well the intrinsic catalytic activities with their sulfur-metal bond energies [29]. As a consequence, intermediate sulfur-metal bond energies of mixed Co(Ni)-Mo sites provide the optimal surface concentrations for the reactive species involved in the kinetically limiting step of toluene hydrogenation: -SH groups and toluene.…”

Highly Active Low Cobalt Content-Based Bulk MoS2 Hydrodesulfurization Catalysts with a Unique Impact of H2S

“…H 2 S in uence on the HDS reaction has been discussed extensively in various studies [29][30][31][32][33][34][35], which consensually suggested that H 2 S suppresses the DDS route, whilst having very little impact on the HYD route. In contrast, several research groups, including our own, have reported that some transition metal sul de catalysts can e ectively promote the HYD reaction when they are carried out in the presence of H 2 S [36][37][38]. Guernalec et al [38] correlated this positive behavior to the increase of the -SH concentration on the catalyst surface.…”

“…In contrast, several research groups, including our own, have reported that some transition metal sul de catalysts can e ectively promote the HYD reaction when they are carried out in the presence of H 2 S [36][37][38]. Guernalec et al [38] correlated this positive behavior to the increase of the -SH concentration on the catalyst surface. However, our obtained results represent a unique catalytic Figure 6: E ect of the Co content on the HDS activity (a) and the relationship between the activity and the selectivity (b).…”

Transition metal sulfides on zeolite catalysts for selective ring opening

“…These TMS present a nearly spherical shape. Due to its crystallographic properties, rhombohedral Cr2S3 forms rather large plate -like particles as observed by Figure 2 [21,22].…”

“…The concentrations of Brönsted and Lewis acid sites after desorption at 150,250 and 350 °C were calculated using the extinction coefficients εBA (1.67) and εLA (2.22) determined by Emeis et al 23 As compared to the zeolitic support alone, the introduction of the TMS generally reduces the Brönsted acidic site (BAS) content and strength except in the case of RuS2 with an increase of BAS and with Cr sulfide where a high content of Lewis site was found. This sulfide belongs exhibit a low M-S bond strength [21] and the lamellar particles can be easily reduced at the surface to generate Lewis sites. For the variations observed on the other sulfides, we do not have yet any clear explanation.…”