Electron Tomography Reveals the Active Phase–Support Interaction in Sulfidic Hydroprocessing Catalysts

Conventional two-dimensional (2D) transmission electron microscopy of sulfidic hydroprocessing catalysts can be deceiving and give the impression that parts of the support are overloaded with active phase. High-angle annular dark field scanning transmission electron microscopy tomography reveals details on the morphology of MoS2 crystallites and their interaction with the Al2O3 and TiO2 support particles. The three-dimensional (3D) reconstruction shows that the active phase is mainly present as MoS2 single slabs of various shapes aligned with the support. It becomes clear that the surface of the support particles is, in fact, only partly covered by the active phase and the pores remain accessible for reactant molecules.