Heavy oil hydroprocessing

A hydroprocess comprising introducing feed oil, hydrogen, water, hydrogen sulfide and hydrogenation catalyst to a hydroprocessing zone, the weight ratio of water to oil being between 0.005 and 0.25, the partial pressure of hydrogen sulfide being between 20 and 400 psi, the hydrogen partial pressure being between 350 and 4500 psi, the temperature being between 650.degree. and 1000.degree. F., said water being at least partially in the vapor phase, said hydrogenation catalyst comprising sulfided molybdenum which is present in said hydroprocess in the molybdenum as metal to oil weight ratio of 0.0005 to 0.25 with said catalyst having been prepared by reacting aqueous ammonia and molybdenum oxide with a weight ratio of ammonia to molybdenum as metal of 0.1 to 0.6 to form aqueous ammonium molybdate, reacting said aqueous ammonium molybdate with hydrogen sulfide to form a precursor slurry, mixing said precursor slurry with feed oil, hydrogen and hydrogen sulfide and heating said mixture at a pressure between 500 and 5000 psi so that it is within the temperature range of 150.degree. to 350.degree. F. for a duration of 0.05 to 0.5 hours, further heating said mixture so that it is within the temperature range of 351.degree. to 750.degree. F. for a time duration of 0.05 to 2 hours, and said hydroprocess to include recycling to said hydroprocessing zone a hydrogen-hydrogen sulfide stream separated from the hydroprocessing zone effluent wherein the partial pressure of hydrogen sulfide is at least 20 psi so that the circulation of hydrogen sulfide is greater than 5 SCF per pound of molybdenum as metal and the hydrogen circulation rate is between 500 to 10,000 SCFB.