Hydroprocessing of vacuum residues: relation between catalyst activity, deactivation and pore size distribution

Four catalysts with different unimodal and bimodal pore size distributions having different proportions of meso- and macropores were studied. The performance of the catalysts in terms of activity and selectivity as well as deactivation in selected hydrotreating reactions was examined using Kuwait vacuum residue as feedstock. The effect of catalyst pore size was significantly different for different reactions. For sulfur removal (HDS), a unimodal pore catalyst with maximum pore volume in the medium mesopore range (10–25 nm diameter) showed the highest activity. For hydrodemetallation (HDM) and hydrodenitrogenation (HDN) reactions, large-pore catalysts, having a major proportion of their pore volume in 100–300 nm diameter pores, were more effective. Bimodal pore catalysts having large amounts of narrow pores showed a higher rate of deactivation than unimodal pore catalysts with a maximum amount of medium mesopores.