Patent ID: 7374660

Claim:
A process for producing propylene comprising the steps of: (a) feeding a naphtha stream comprising from about 5 to about 40 wt. % paraffins and from between about 15 to about 70 wt. % olefins to a process unit comprising a reaction zone, a stripping zone having a dense phase and a dilute phase, a catalyst regeneration zone, and a fractionation zone; (b) contacting the naphtha stream with a fluidized bed of catalyst in the reaction zone to form a cracked product, the catalyst comprising a zeolite having an average pore diameter of less than about 0.7 nm and wherein the reaction zone is operated at a temperature from about 500 to about 650° C., a hydrocarbon partial pressure of about 10 to about 40 psia, (about 70 to about 280 kPa) and a hydrocarbon residence time of about 1 to about 10 seconds; (c) passing the catalyst through said stripping zone; (d) passing the stripped catalyst from the stripping zone to the catalyst regeneration zone where the catalyst is regenerated in the presence of an oxygen-containing gas; (e) recycling the regenerated catalyst to the reaction zone; (f) fractionating the cracked product to produce a C 3 fraction containing propylene, a C 4 fraction containing olefins, and optionally a C 5 fraction containing olefins; (g) recycling at least a portion of the C 4 fraction containing olefins to a dilute phase secondary reaction zone above and separate from the dense phase stripping zone; and (h) optionally separating propylene from the C 3 fraction.