Interrelations between initial pore structure, morphology and distribution of accumulated deposits, and lifetimes of hydrodemetallisation catalysts

The functioning of commercial HDM catalysts, experiencing conditions of industrial use in residual feedstocks upgrading reactors is analysed, in order to derive the essential physical and chemical processes that determine their deactivation. A mathematical model of this evolution is presented as an attempt to integrate this analysis into computer simulations for improved reliability of lifetimes predictions. A method to obtain accelerated aging data on HDM catalysts at the bench scale is presented, with examples of results. A method is given to combine such results with EPMA analysis of used catalyst pellets in order to determine the Ultimate Storage Capacity intrinsic to the catalyst's pore structure. Selected results of an High Resolution Electron Microscopy study of microtome thin foiled used HDM catalyst pellets are presented: they show for the first time the nature, morphology and structure of metal sulfides deposits at the micropore level, and support the “discrete” mode of deposition theory. Model predictions and experimental deactivation results are compared, and the limitations of the model discussed. Unsolved questions are listed for future research.