VARIATION OF THE DISPERSION OF ACTIVE PHASES IN COMMERCIAL NICKEL MOLYBDENUM-GAMMA-ALUMINA HYDROTREATING CATALYSTS DURING OXIDATIVE REGENERATION

The structural properties of commercial nickel-molybdenum/ gamma -alumina hydrotreating catalysts, in both the sulfide and oxide form, were studied as a function of laboratory treatment simulating the conditions the catalysts would encounter during their lifetime. X-ray diffraction was used to assess the degree of dispersion of the active phases, and regeneration conditions which sintered these phases were identified. Moderate regeneration conditions were found to be effective in reversing oxide agglomeration resulting from previous abuse of the catalysts. This observation led to the development of a procedure capable of redispersing the oxide phase over the support. It was possible to recover the original oxide dispersion found in the fresh catalyst, but subsequent sulfiding produced a molybdenum disulfide phase composed of crystallites excessively large in one direction.