A Geometrical Model of Hydrotreating Catalysts ‐ Prediction of Catalytic Activity Variations with Composition

A geometrical model of the active phase of hydrotreating catalysts is proposed. The existence of MoS2 patches on a carrier and the reactivity of the edge sites of these patches are the two experimental observations used for the development of this model. The promotor effect is taken into account by an edge decoration of the patches. A partial loss of promotor ions into the Al2O3 carrier and formation of a promotor bulk sulphide are also considered. The specific activity for a given reaction, the amount of chemisorbed oxygen and promotor effect are predicted and can be compared to experimental results previously published in the literature by different authors. The good fitting obtained put in evidence that both HDS, hydrogenation and O2 chemisorption Involve the edge sites (unpromoted or promoted) of the patches. The model has a general character and may apply to MoS2 or WS2, promoted or unpromoted, supported and unsupported hydrotreating catalysts.