Fluid catalytic cracking process for conversion of residual oils

A fluid catalytic cracking process comprising the steps of:

• a. contacting a feedstream consisting essentially of a residual oil selected from the group consisting of whole crudes and atmospheric reduced crudes, said residual oil containing at least 2 wt. % Conradson carbon, with regenerated zeolite-containing catalyst in a riser reaction zone maintained at catalytic cracking conditions selected to produce a coke yield numerically less than the sum of the wt. % Conradson carbon in the feedstream plus about 4 wt. % carbon, said cracking conditions including a temperature within the range of about 850.degree. F. to about 1000.degree. F. a pressure within the range of about atmospheric to about 40 psig., a hydrocarbon residence time of less than 10 seconds, and a catalyst to oil ratio of from about 3 to about 6;
• b. passing said feed and catalyst through said reaction zone maintained at said cracking conditions to form a mixture consisting of spent catalyst and hydrocarbons;
• c. discharging the mixture into cyclone separation means at separation conditions to effect the separation of hydrocarbons from spent catalyst and recovering the hydrocarbons;
• d. passing spent catalyst from said separation means into a spent catalyst stripping zone and therein stripping spent catalyst at stripping conditions to remove adsorbed and interstitial hydrocarbons therefrom to form stripped spent catalyst containing coke thereon;
• e. passing at least a portion of stripped spent catalyst to a first dense bed of fluidized particulated material maintained in a regeneration zone at a temperature within the range of about 1150.degree. F. to about 1400.degree. F., a superficial gas velocity within the range of about 3 to about 10 feet per second, and a catalyst residence time of less than about 2 minutes, passing fresh regeneration gas upwardly through said bed and therein oxidizing coke to produce partially spent regeneration gas, containing CO, and regenerated catalyst;
• f. passing a suspension of said regenerated catalyst and partially spent regeneration gas upwardly from said bed through a dilute phase transport riser of smaller cross-sectional area than said bed and therein converting at a temperature within the range of about 1200.degree. F. to about 1500.degree. F. and a superficial gas velocity in the range of about 10 to about 25 feet per second CO to CO.sub.2 to produce spent regeneration gas and transferring heat of CO combustion to the regenerated catalyst in the suspension;
• g. discharging said suspension from the upper end of said riser and separating regenerated catalyst from spent regeneration gas and passing regenerated catalyst into a second dense bed of particulate material;
• and,
• h. passing freshly regenerated catalyst from said second dense bed to said riser reaction zone to step (a) above.