Patent ID: 6388152
Filing Date: 2002-05-14
Classification: C10G

Abstract:
A process for producing polypropylene comprising the steps of:(a) feeding a naphtha stream comprising from about 10 to 30 wt. % paraffins and between about 15 to 70 wt. % olefins to a process unit comprising a reaction zone, a stripping zone, 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 500Â° C. to 650Â° C., a hydrocarbon partial pressure of 10 to 40 psia, a hydrocarbon residence time of 1 to 10 seconds, and a catalyst to feed weight ratio between about 4 and about 10, thereby producing a reaction product wherein no more than about 20 wt. % of paraffins are converted to olefins and wherein propylene comprises at least about 90 mol. % of the total C3 products; (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 C3 fraction, a C4 fraction rich in olefins, and optionally a C5 fraction rich in olefins; (g) passing the C4 fraction to the reaction zone or the stripping zone, or both; and, (h) separating propylene from the C3 fraction and polymerizing the propylene to form polypropylene.