METAL-DEPOSITION AND DEACTIVATION OF HYDRODEMETALATION CATALYSTS

Nickel deposition on sulfided and unsulfided CoMO/gamma-Al2O3 hydrodemetallation catalysts were investigated. Both element mapping and X-ray microanalysis from scanning transmission electron microscopy showed that the elemental distribution of deposited nickel were correlated with metal distributions of cobalt, but not with elemental distributions of molybdenum. The probable reason for the preferentiality is migration of the nickel deposition rather than deposition kinetics. Random sphere model calculations showed that segregated large crystallites of nickel deposition lead to less deactivation, in comparison with uniform layers of nickel deposition.