Fluid catalytic cracking process for conversion of residual oils

Claim 1

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° F. to about 1000° 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° F. to about 1400° 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° F. to about 1500° F. and a superficial gas velocity in the range of about 10 to about 25 feet per second CO to CO 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.