Hydrocarbon catalytic cracking process

Claim 1

In a process which comprises contacting a hydrocarbon feed with a cracking catalyst in a cracking zone under cracking conditions to produce a lower boiling gasoline fraction and thereafter heating the deactivated catalyst in the presence of oxygen in a regeneration zone to a temperature in the range of 800° to 1600° F. until the concentration of carbon on the catalyst is less than 0.3 weight percent; the improvement which comprises conducting the cracking process until the concentration of metal contaminants on the catalyst is at least 1500 ppm nickel equivalents, determining the carbon dioxide and carbon monoxide concentrations in the gaseous effluent withdrawn from said regeneration zone, and adjusting the rate of flow in said hydrocarbon feed to said cracking zone of a treating agent selected from the group consisting of antimony, bismuth, manganese and compounds of such treating agents convertible to the oxide form so as to maintain a volume ratio of carbon dioxide to carbon monoxide in said gaseous effluent of at least 2.2.