Fluid catalytic cracking of heavy petroleum fractions

A process for the fluid catalytic cracking of hydrocarbon feedstocks containing metal compounds and organic sulfur compounds wherein the sulfur content of said feedback is in the range from about 0.1 weight percent to about 12 weight percent, wherein (i) metal deposits on the used cracking catalyst are deactivated in sufficient amounts to reduce hydrogen and coke formation during said cracking, (ii) sulfur oxide emissions from sulfur-containing coke deposits on the used cracking catalyst are reduced in amount, (iii) coke deposits on the used cracking catalyst are reduced in amount sufficiently by regeneration whereby the said catalyst is suitable for re-use, which process comprises;

• (a) cracking said feedstock at a temperature from about 850.degree. F. to about 1500.degree. F. in a reaction zone in contact with fluidized solid particles, the said particles comprising a cracking catalyst and at least one metallic reactant in the same or different ones of said solid particles, said metallic reactant consisting essentially of one or more members selected from the group consisting of sodium, scandium, titanium, chromium, molybdenum, manganese, cobalt, nickel, antimony, copper, zinc, cadmium, the rare earth metals, lead, their compounds and mixtures thereof, and wherein said metallic reactant is present in sufficient amount to effect a reduction of at least 50% of the sulfur oxides produced by oxidation of the sulfur-containing coke deposits;
• (b) withdrawing of said particles from said reaction zone;
• (c) subjecting said particles to a reducing zone wherein carbon monoxide from limited combustion of said sulfur-containing coke deposits is present in a concentration from about 4 to 14 volume percent;
• (d) withdrawing said particles from said reducing zone;
• (e) subjecting the said particles to an oxidizing zone containing sufficient oxygen to raise the excess molecular oxygen in the flue gas emitted from said oxidizing zone to over 0.1 volume percent and wherein the carbon monoxide content in said flue gas is less than about 4 volume percent;
• (f) withdrawing the said particles from said oxidizing zone whereby the said particles are in a condition suitable for re-use in the said reaction zone.