Patent ID: 7323099
Filing Date: 2008-01-29
Classification: C07C,C10G

Abstract:
1. A two stage process for selectively producing C 2 to C 4 olefins from a heavy hydrocarbonaceous feed, the process comprising the steps of: a) contacting a heavy hydrocarbonaceous feed with a mixture of a large-pore zeolitic catalytic cracking catalyst having an average pore diameter greater than about 0.7 nm and a medium-pore zeolitic catalytic cracking catalyst having an average pore diameter less than about 0.7 nm in a first reaction stage comprising a fluid catalytic cracking unit to convert said heavy hydrocarbonaceous feed to lower boiling reaction products; b) fractionating said lower boiling reaction products into at least a propylene-rich vapor stream and a naphtha boiling range fraction, the naphtha boiling range fraction comprising between about 10 and about 30 wt. % paraffins and between about 15 and about 70 wt. % olefins; c) collecting said propylene-rich vapor stream; d) contacting said naphtha boiling range fraction with a second catalyst comprising between about 10 and about 50 wt. % of a crystalline zeolite having an average pore diameter less than about 0.7 nm in a second reaction stage comprising a process unit comprising a reaction zone, a stripping zone, a second catalyst regeneration zone, and a fractionation zone, wherein the naphtha boiling range fraction is contacted with the second catalyst in the reaction zone at reaction conditions which include temperatures ranging from about 500 to about 650° C. and a hydrocarbon partial pressure from about 10 to about 40 psia (about 70 to about 280 kPa) and a catalyst to second stage feed weight ratio of about 4 to about 10, and wherein propylene comprises at least about 75 mol. % of the total C e) collecting the C f) passing the second catalyst particles through the stripping zone wherein volatiles are stripped therefrom with steam; g) passing the stripped second catalyst particles to the regeneration zone where coke is combusted from the second catalyst resulting in hot catalyst particles; h) recycling the hot second catalyst particles to the second stage reaction zone; and i) separating the propylene from the C