Two stage fluid catalytic cracking process for selectively producing c2 to c4 olefins

Abstract From the Canadian patent

A two stage process for selectively producing C2 to C4 olefins from a gas oil or resid. The gas oil or resid is reacted in a first stage comprised of a fluid catalytic cracking unit wherein it is converted in the presence of conventional large pore zeolitic catalyst to reaction products including a , naphtha boiling range stream. The naphtha boiling range stream is introduced into a second stage comprised of a process unit containing a reaction zone a , stripping zone, a catalyst regeneration zone and a fractionation zone. The , naphtha feedstream is contacted in the reaction zone with a catalyst containing from about 10 to 50 wt.% of a crystalline zeolite having an average pore …