Patent ID: 7261807

Claim:
A fluid cat cracking process with increased C 3 olefins production which comprises the steps of: (a) a step consisting essentially of contacting an FCC feed consisting essentially of oils having an initial boiling point greater than 232° C. (450° F.) with a particulate, hot, regenerated cracking catalyst comprising large and medium pore zeolite components in a first cracking reaction zone at reaction conditions effective to catalytically crack said feed and produce first lower boiling hydrocarbons comprising naphtha crackate boiling in the C 5 -430° F. range, propylene-containing light olefins, and spent catalyst particles which contain strippable hydrocarbons and coke; (b) separating said first lower boiling hydrocarbons produced in step (a) from said spent catalyst particles in a first separation zone and stripping said catalyst particles in a stripping zone, to remove said strippable hydrocarbons to produce stripped, coked catalyst particles, wherein said first separation and stripping zones are in the same vessel; (c) separating a naphtha crackate fraction boiling in the 60–300° F. range from the first lower boiling hydrocarbons separated in step (b); (d) contacting at least a portion of said naphtha crackate fraction produced in step (c) with said hot, regenerated, particulate cracking catalyst in a second and separate cracking reaction zone at reaction conditions effective to catalytically crack said naphtha and produce second lower boiling hydrocarbons comprising more propylene-containing light olefins, and spent catalyst particles which contain strippable hydrocarbons and coke; (e) separating said second lower boiling hydrocarbons from said spent catalyst particles in a second and separate separation zone and stripping said particles in said stripping zone, to remove said strippable hydrocarbons to produce stripped, coked catalyst particles, provided that said second lower boiling hydrocarbons separated in said separate separation zone are not mixed with first riser reaction products; (f) passing said stripped, coked catalyst particles produced in steps (b) and (e) into a regeneration zone in which said particles are contacted with oxygen at conditions effective to bum off said coke and produce said hot, regenerated catalyst particles; (g) passing said hot, regenerated particles into said first and second cracking reaction zones, each of which is in a separate riser; and, (h) passing said first lower boiling hydrocarbons from said first separation zone and said second lower boiling hydrocarbons from said second separation zone to a fractionation system for further processing, wherein the process conditions in the first and second cracking reaction zones are such that propylene comprises at least 90 mol % of the total C 3 products in the first and second lower boiling hydrocarbons.