Catalyst treatment and flow conditioning in an FCC reactor riser

A process for converting a charge stock comprising normally liquid hydrocarbons in a riser conversion zone with an active fluid catalytic cracking catalyst which comprises:

• (a) passing suspension consisting essentially of hot regenerated active fluid catalytic cracking catalyst in a lift gas comprising hydrocarbons including not more than 10 mole % C.sub.3 and heavier hydrocarbons (calculated on a water-free basis) through a first treatment section of said riser conversion zone at treatment conditions selected to selectively carbonize reaction sites on the catalyst prior to any contact with the charge stock while simultaneously accelerating the catalyst to a velocity sufficient to provide turbulent dilute flow at the point of contact with the charge stock;
• and,
• (b) introducing said charge stock into said suspension at a locus in said riser conversion zone downstream of said treatment section to form a mixture of catalyst, charge stock and lift gas having the catalyst relatively uniformly distributed therethrough and thereafter reacting the charge stock with the catalyst in the remaining downstream section of said riser conversion zone at reaction conditions sufficient to effect the desired conversion.