Method for catalytic cracking heavy oils

Claim 1

In a riser cracking operation processing hydrocarbon feeds of different cracking characteristics, the method for producing high yields of gasoline boiling product which comprises, passing a hydrocarbon feed comprising fresh atmospheric gas oil admixed with freshly regenerated crystalline zeolite catalyst as a suspension at an elevated cracking temperature upwardly through an initial portion of a riser conversion zone, for a contact time selected to particularly produce one of gasoline and distillate boiling product, charging a second high coke producing hydrocarbon fraction selected from the group consisting of gas oil products of thermal cracking, heavy residual oil products of catalytic cracking and distress stocks comprising substantial amounts of polynuclear aromatics into said upwardly flowing suspension at a level from 10 to about 30 feet above the atmospheric gas oil charge level under conditions and at a temperature maintaining a riser conversion zone outlet temperature within the range of 900° F. to 1100° F., and recovering an improved yield of gasoline product over that obtainable at the same outlet temperature by charging all of the hydrocarbon feeds to the bottom of the riser conversion zone.