Hydrotreating process using porous mullite

In a process for treating heavy hydrocarbon oil which contains heavy metals and/or sulfur comprising contacting said oil with hydrogen in the presence of a catalyst and recovering a hydrocarbon product having reduced content of heavy metals and/or sulfur, the improvement which comprises using as the catalyst one or more catalytic metals of the group consisting of cobalt, nickel, molybdenum and tungsten impregnated on porous supporting bodies consisting essentially of mullite crystals, and optionally free silica, said bodies having a molar ratio of Al.sub.2 O.sub.3 /SiO.sub.2 in excess of 0.50 and up to about 1.65 and having few, if any pores <100 A in diameter and up to about 0.4 cc/g of pores having diameters >600 A, said porous supporting bodies having been prepared by the method comprising calcining bodies of kaolin clay at a temperature in the range of about 1150.degree. C. to about 1350.degree. C. until the clay is converted into mullite and free silica, leaching the resulting bodies of calcined clay with an alkaline aqueous solution to remove at least a portion of said free silica, washing the leached clay bodies to remove alkali ions, drying and then recovering the resulting porous supporting bodies consisting essentially of mullite crystals.