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CoMo additive-impregnated dried catalysts are studied, exploring the ''CoMoS'' active phase features by combining X-ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM) and catalytic tests. Starting from different polyoxomolybdate precursors, additive-impregnated dried, additive-free dried and calcined catalyst performances are compared. TEM reveals that the mean particle sizes are about 3.1 nm and do not depend on the catalytic precursors except for the additivefree dried catalysts exhibiting higher lengths: 3.7 nm. XPS quantification of the Mo species shows that 75 mol% of the Mo species are present in the MoS 2 phase whatever the preparation route. This value is slightly enhanced (ca. 85%) with additive impregnation. The molybdenum to aluminium surface coverage ratio (Mo/Al) ranking is found to be as follows: additive-free dried o additive-impregnated dried o calcined. However, this ranking is not significantly modified by the impregnating solution used, and the behaviour is similar for the cobalt to aluminium ratio (Co/Al). A geometrical model combining XPS quantification of the crystallite's Co/Mo ratio and DFT calculations is used to establish a correlation with the catalytic results obtained in toluene hydrogenation. It is shown that the catalytic performances of additive-free dried, additive-impregnated dried and calcined catalysts directly correlate the number of mixed Co-Mo sites present at the MoS 2 edges. DFT calculations highlight that the adsorption step of toluene is thermodynamically favored on the mixed Co-Mo site located at the M-edge. As a consequence, this study suggests that the various routes of preparation leading to different catalytic performances would not lead to new types of active sites or morphology but rather to a different number of mixed sites present at the edges.

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Résumé -Étude comparative de la décoration optimale par le promoteur des phases CoMoS et NiMoS actives en hydrotraitement -Dans le but d'acquérir une meilleure compréhension de la morphologie et la teneur en promoteur de la phase active des catalyseurs d'hydrotraitement dans les conditions de l'hydrotraitement, une étude multi-technique a été entreprise sur une série de catalyseurs NiMoP avec des ratios Ni/Mo variables. La combinaison de la spectroscopie photoélectronique-X, de la microscopie électronique à transmission, de la modélisation moléculaire ab initio et de tests catalytiques d'hydrogénation du toluène a permis d'aboutir à un modèle morphologique qui a été comparé à une précédente étude menée sur une série analogue promue par le cobalt. Cette étude confirme l'importance de la présence de sites mixtes Ni-Mo sur les bords des cristallites, en particulier sur le bord M-edge pour les réactions d'hydrogénation. Ces résultats permettent d'orienter la mise au point de nouveaux catalyseurs dans le but de maximiser leurs performances. Abstract -A Rational Comparison of the Optimal Promoter Edge Decoration of HDT NiMoS vs CoMoS Catalysts -In order to gain a better understanding of the morphology and promoter edge content of the active phase of industrial HDT NiMoP catalysts in working conditions, a multi-technique study has been undertaken on a series of NiMoP catalysts with various Ni/Mo ratios. The combination of X-ray Photoelectron Spectroscopy (XPS), Transition Electron Microscopy (TEM), Density Functional Theory (DFT) modeling and catalytic testing (toluene hydrogenation) provided data to build a morphological model of NiMoS nanocrystallites. A parallel has been established with their CoMoS