Cracking blends of gas oil and residual oil

In a catalytic cracking process unit wherein a gas oil feed is cracked in a cracking zone at elevated temperature in the presence of cracking catalyst, the cracking catalyst is regenerated in a regeneration zone by burning coke off the catalyst and catalyst is circulated between the cracking zone and the regeneration zone, the improvement for obtaining a naptha product of improved octane number comprising introducing sufficient of a nickel and vanadium metals containing heavy feedstock with said gas oil feed introduced into the cracking zone to deposit nickel and vanadium metals on said catalyst and raise the nickel and vanadium metals-content of said catalyst to a level ranging from about 3,000 to 30,000 parts per million of said metals expressed as equivalent nickel based on the weight of the catalyst and maintaining said nickel and vanadium metals level on the catalyst by withdrawing high nickel and vanadium metals-containing catalyst and adding low nickel and vanadium metals-containing catalyst to the regeneration zone.

In a catalystic cracking processing unit wherein a gas oil feed is cracked in a cracking zone at elevated temperature in the presence of cracking catalyst, the cracking catalyst is regenerated in a regeneration zone by burning coke off the catalyst and catalyst is circulated between the cracking zone and the regeneration zone, the improvement for obtaining a naptha product of improved octane number comprising introducing sufficient of a nickel and vanadium metals containing heavy feedstock with said gas oil feed introduced into the cracking zone to deposit nickel and vanadium metals on said catalyst and raise the nickel and vanadium metals-content of said catalyst to a level ranging from substantially larger than 600 to 70,000 parts per million of said metals expressed as equivalent nickel based on the weight of the catalyst and maintaining said nickel and vanadium metals level on the catalyst by withdrawing high nickel and vanadium metals-containing catalyst and adding low nickel and vanadium metals-containing catlayst to the regeneration zone.