Catalyst composition and method for hydroprocessing petroleum feedstocks

A catalyst composition useful in the hydroprocessing of a sulfur- and metal-containing hydrocarbon feedstock comprises 1.0-5.0 weight percent of an oxide of nickel or cobalt and 10.0-25.0 weight percent of an oxide of molybdenum, all supported on a porous alumina support in such a manner that the molybdenum gradient of the catalyst has a value of less than 6.0 and 15-30% of the nickel or cobalt contained in the catalyst is in an acid extractable form. The catalyst is further characterized by having a total surface area of 150-210 m2/g, a total more volume of 0.50-0.75 cc/g, and a pore size distribution such that pores having diameters of less than 100A constitute less than 25.0%, pores having diameters of 100-160A constitute 70.0-85.0% and pores having diameters of greater than 250A constitutes 1.0-15.0% of the total pore volume of the catalyst. A method for the hydroprocessing of a sulfur- and metal-containing hydrocarbon feedstock comprises contacting the feedstock with the abovedescribed catalyst and hydrogen in a maner such that the catalyst is maintained at isothermal conditions and is exposed to a uniform quality of feed. The method is particularly effective in achieving desired levels of hydrodesulfurization in vacuum residual feedstocks.