Use of lift gas in an FCC reactor riser

A process for converting normally liquid hydrocarbons with an active fluid catalytic cracking catalyst which comprises: (a) passing a suspension of hot regenerated active fluid catalytic cracking catalyst in a lift gas comprising hydrocarbons including not more than 10 mole % C3 and heavier hydrocarbons through a horizontally oriented lower portion of a riser conversion zone at a velocity of from about 1.8 to less than 12.2 meters per second, and for a residence time from about 0.5 to about 15 seconds, the ratio of catalyst to hydrocarbon in said lift gas being greater than 80; and (b) introducing the normally liquid hydrocarbons into the upflowing suspension at a vertically orientated locus in the riser conversion zone downstream of the lower portion to form a catalyst-hydrocarbon mixture wherein the temperature and residence time are sufficient to effect the desired conversion. The process is particularly useful for the treatment of a heavy residual feedstock.