Patent ID: 7267759

Claim:
A process for producing increased amounts of propylene from naphtha-boiling-range feedstreams in a process unit comprising at least a reaction zone, a stripping zone, a regenerator zone, and at least one fractionation zone, which process comprises: (a) fractionating said naphtha-boiling-range feedstream to produce a C 6 -rich fraction and a C 6 -lean fraction, wherein the C 6 -rich fraction contains at least 50 wt % C 6 compounds; (b) injecting at least a portion of said C 6 -lean fraction into the reaction zone, said reaction zone containing a cracking catalyst comprising at least one molecular sieve having an average pore diameter of less than about 0.7 nm wherein said C 6 -lean fraction contacts said zeolite cracking catalyst under effective conditions thereby resulting in at least spent catalyst particles having carbon deposited thereon and a product stream; (c) injecting at least a portion of said C 6 -rich fraction at a place in the process unit selected from: i) downstream of the C 6 -lean fraction; ii) the stripping zone; and iii) a dilute phase above the stripping zone; (d) contacting at least a portion of said spent catalyst particles with a stripping gas in the stripping zone under conditions effective at removing at least a portion of any volatiles therefrom thereby resulting in at least stripped spent catalyst particles; (e) regenerating at least a portion of said stripped spent catalysts in a regeneration zone in the presence of an oxygen-containing gas under conditions effective at burning off at least a portion of said carbon deposited thereon thereby producing at least regenerated catalyst particles; (f) recycling at least a portion of said regenerated catalyst particles to said reaction zone; (g) fractionating at least a portion of said product stream of step (b) to produce at least a fraction rich in propylene; and (h) collecting at least a portion of the fraction rich in propylene.