Studies on an aged H-Coal catalyst

Abstract

A standard H-Coal catalyst, American Cyanamid HDS 1442A CoMo/γAl 2O 3, was studied in its fresh, aged, and aged regenerated states. The aged catalyst contained approximately 20 wt% coke and 5 wt% metal contaminants; coke was evenly distributed throughout the catalyst, whereas the metals were concentrated near (100–200 μm) the catalyst exterior. The BET surface area and pore volume of the aged catalyst were reduced by about 50% of that measured for fresh catalyst. Catalytic studies using the model compounds thiophene, hexene and isooctene allowed assessment of three basic activity functions, viz., hydrodesulfurization (HDS), hydrogenation and cracking. Compared with the fresh catalyst, the aged catalyst had about 20% intrinsic HDS and hydrogenation activity remaining and virtually no cracking activity. In addition, a lower diffusivity contributed to catalyst activity loss in the aged catalyst extrudates. Regeneration in air at 450°C only partially restored the original catalyst HDS activity, but almost completely restored hydrogenation and cracking activity. Metal deposits appeared to mostly affect HDS activity, whereas coke had greatest effect on cracking activity. These results show that aging affects the various catalytic functions differently.