Process for the hydrocracking of hydrocarbon oils under reaction conditions so as toretain substantial amounts of aromatics in the naphtha product

Claim 1

THE PROCESS FOR HYDROCRACKING A PETROLEUM FRACTION WHICH BOILS ABOVE ABOUT 400*F., WHICH IS SUBSTANTIALLY FREE OF ASPHALTIC MATERIAL, WHICH CONTAINS A SUBSTANTIAL AMOUNT OF AROMATIC HYDROCARBONS AND WHICH CONTAINS LESS THAN ABOUT 20 P.P.M. OF NITROGENOUS IMPURITIES TO PRODUCE SUBSTANTIAL MOUNTS OF HYDROCARBONS BOILING IN THE GASOLINE RANGE WITH CONCOMITANT HIGH RETENTION OF AROMATICS, WHICH PROCESS COMPRISES CONTACTING SAID HYDROCARBON FEED STOCK WITH HYDROGEN IN THE PRESENCE OF A HYDROGENATING CATALYST COMPOSITED WITH AN ACIDIC SILICEOUS CRACKING CATALYST, AT A HYDROGEN PARTIAL PRESSURE OF BETWEEN ABOUT 1500 AND 4000 P.S.I. AND AT A MINIMUM LIQUID HOURLY SPACE VELOCITY GIVEN BY THE FORMULA LHSV=2.0+0.001P-0.02A, WHERE P=HYDROGEN PARTIAL PRESSURE IN P.S.I.G. AND A=AROMATIC CONTENT OF THE FEED IN PERCENT BY VOLUME, AT A TEMPERATURE OF BETWEEN ABOUT 700* AND 900*F., SAID CONDITIONS OF TEMPERATURE, PRESSURE AND SPACE VELOCITY BEING ADJUSTED TO MAINTAIN A CONVERSION LEVEL OF FROM ABOUT 40% TO 75% DURING THE ON-STREAM REACTION WHEREBY A HYDROCRACKED 180*-400*F. NAPHTHA PRODUCT WHICH CONTAINS AROMATIC HYDROCARBONS IN AMOUNT AT LEAST APPROXIMATELY 60% THAT OF THE FEED IS OBTAINED.