Abstract: A process for increasing the yield of C.sub.3 and C.sub.4 olefins by injecting light cat naphtha together with steam into an upstream reaction zone of a FCC riser reactor. The products of the upstream reaction zone are conducted to a downstream reaction zone and combined with fresh feed in the downstream reaction zone.

Abstract: This invention is directed to a feed injector for a fluid catalytic cracking reaction zone, which feed injector provides improved oil atomization and dispersion. The injector comprises a straight-pass conduit section, in which a feed oil and steam are premixed, and a terminal section, where the oil is atomized and dispersed by a generally fan-shaped distributor. The feed injector produces a substantially flat spray pattern across the direction of catalyst flow in the catalyst/oil contacting section of the catalytic cracking reaction zone. Improved product yield and lower coke and light gas yields are obtained.