such as zeolite y introduced through a valved conduit means such as standpipe 6 provided with a flow control valve 8 because the temperature of the hot regenerated catalyst is in the range from about 1200 u00b0 f 676 7 u00b0 c to about 1350 u00b0 f 732 2 u00b0 c a suspension of hydrocarbon vapors is quickly formed and flows upward through the riser 4 the riser 4 is flared gently outward into a region 5 through which catalyst and entrained hydrocarbons are flowed being afforded in this region 5 the contact time preselected to provide desired cracked products catalyst particles and the gasiform products of conversion continue past region 5 and are discharged from the top of the riser into one or more cyclone separators 14 housed in the upper portion 17 of the vessel indicated generally by reference numeral 19 riser 4 terminates in a bird cage discharge device or an open end 34 t 34 connection may be fastened to the riser discharge which is not typically directly connected to the cyclonic catalyst separation means the effluent from riser 4 comprises catalyst particles and hydrocarbon vapors which are led into the cyclonic separators 14 which effect separation of catalyst from hydrocarbon vapors such vapors pass into a plenum chamber 16 and thence are removed through conduit 18 for recovery and further processing hydrocarbon vapors from cyclone 14 are discharged to a plenum chamber 16 from which they flow through conduit 18 for further processing and recovery typically to a fractionator column where the products of cracking are separated into preselected fractions catalyst separated from the vapors descends through dipleg 20 to.