Both CoMo and Ni-CoMo catalyst supported over gamma-alumina were synthesized and compulsively deactivated by coking from 1,5-hexadiene. The coked catalysts, containing similar to 8.8 wt% carbon and similar to 7 wt% sulfur, were regenerated by oxidative burnoff at various temperatures in the range of 300-700 degrees C. The catalyst regenerated at each temperature was characterized by various techniques; i.e., BET, XRD, XPS, and TPR. During regeneration, physicochemical properties such as surface area, crystallinity, reducibility, and metal distribution changed significantly with the regeneration temperature. Increase in the dispersion of promoter species (cobalt or nickel) was observed in the catalysts regenerated at low temperatures and this gave rise to the enhancement of activity in comparison to the fresh catalyst. On the other hand, promoters migrated into the sublayer of alumina support at higher temperatures and thus resulted in the formation of PAl2O4 (P = Co or Ni) phases. Consequently, the crystallinity of the catalyst increased while the reducibility decreased as the regeneration temperature increased. An abrupt increase in Mo dispersion and a decrease in surface area were observed when the coked catalyst was regenerated at 700 degrees C.