Patent ID: 6106697
Filing Date: 2000-08-22
Classification: C10G

Abstract:
A two stage process for selectively producing C.sub.2 to C.sub.4 olefins from a heavy hydrocarbonaceous feedstock, which process comprises:a) reacting said feedstock, in a first stage comprised of a fluid catalytic cracking unit wherein it is converted in the presence of a large pore zeolitic catalytic cracking catalyst having an average pore diameter greater than about 0.7 nm and having a crystalline tetrahedral framework oxide component to lower boiling reaction products;b) fractionating said lower boiling reaction products into various boiling point fractions, one of which is a naphtha boiling range fraction and one of which is a vapor fraction,c) reacting said naphtha boiling range fraction in a second reaction stage comprised of a process unit comprised of a reaction zone, a stripping zone, a catalyst regeneration zone, and a fractionation zone, wherein the naphtha boiling range fraction contains from about 10 to 30 wt. % paraffins and from about 15 to 70 wt. % olefins, and is contacted in the reaction zone with a catalyst containing from about 10 to 50 wt. % of a crystalline zeolite having an average pore diameter less than about 0.7 nm and silica to alumina molar ratio of less than about 75:1 at reaction conditions which include temperatures ranging from about 500 to 650.degree. C. and a hydrocarbon partial pressure from about 10 to 40 psia, and a catalyst to feed ratio, by weight of about 4 to 10, and wherein propylene comprises at least about 90 mol. % of the total C.sub.3 products;d) collecting the resulting vapor products overhead and passing catalyst particles through the stripping zone wherein volatiles are stripped with steam;e) passing the stripped catalyst particles to a regeneration zone where coke is burned from the catalyst; andf) recycling the hot regenerated catalyst particles to the reaction zone.