Recracking of cat naphtha for maximizing light olefins yields

A fluid catalytic cracking process for upgrading feedstocks to increase yields of C.sub.3 and C.sub.4 olefins while increasing the motor octane number of naphtha which comprises:

• (a) conducting hot regenerated catalyst to a riser reactor containing a downstream and an upstream reaction zone,
• (b) contacting hot catalyst with recycled light cat naphtha product produced by the fluid catalytic cracking process and containing C.sub.5 to C.sub.9 olefins said product having a final boiling point less than about 140.degree. C. and steam in the upstream reaction zone at a temperature of from about 620.degree. to 775.degree. C and a vapor residence time of naphtha and steam of less than 1.5 sec. wherein at least a portion of the C.sub.5 to C.sub.9 olefins present in the light cat naphtha is cracked to C.sub.3 and C.sub.4 olefins,
• (c) contacting the catalyst, cracked naphtha products and steam from the upstream reaction zone with a feedstock having a boiling point range of from about 220.degree. to 575.degree. C. in the downstream reaction zone at a temperature of from about 600.degree. to 750.degree. C. with vapor residence times of less than about 20 sec.,
• (d) conducting spent catalyst, cracked products and steam from the first and second reaction zones to a separation zone,
• (e) separating cracked products including light cat naphtha and steam from spent catalyst and recycling at least a portion of the light cat naphtha product with added steam to the upstream reaction zone in step (b),
• (f) conducting spent catalyst to a stripping zone and stripping spent catalyst under stripping conditions, and
• (g) conducting stripped spent catalyst to a regeneration zone and regenerating spent catalyst under regeneration conditions.