Separation of catalyst from effluent of a fluidized catalytic hydrocarbon conversion process

In a method for the fluid catalytic cracking of petroleum hydrocarbons wherein an ascending essentially cocurrent flow of the vaporous hydrocarbon feedstock and catalyst particulates is effected in an elongated tubular reaction zone;

• the improvement of separating the catalyst particulates from the cracked hydrocarbon stream which comprises discharging said particulates alone by virtue of the inertial momentum associated therewith directly into a catalyst disengaging zone in which there is essentially no net flow of gases under steady state conditions, via an unrestricted downstream extremity opening of said reaction zone while the cracked hydrocarbon stream containing a residual amount of catalyst particulates is diverted laterally prior to said discharging into a cyclonic separation system communicating with the reaction zone near said downstream opening thereof through an opening upstream of and near said downstream extremity opening.