Conversion of alkanes to alkylenes in an external catalyst cooler for the regenerator of a FCC unit

Claim 1

In a process for regenerating a coke-contaminated fluid cracking catalyst in a regeneration zone at a pressure in the range from above 20 psig to about 50 psig and a temperature in the range from about 1200° F. to about 1500° F. (650° C. to 815° C.) while injecting enough oxygen-containing regeneration gas into said regeneration zone to maintain a dense fluid bed of regeneration catalyst, and regenerate the catalyst before returning it to a fluid cracker, the improvement comprising, (a) withdrawing a controlled stream of said regenerator catalyst and introducing it into a dehydrogenation zone at a temperature below those prevailing in said regeneration zone, said dehydrogenation zone being located in a catalyst cooler, externally relative to said cracker and regenerator, the amount of said stream being sufficient to supply the endothermic heat of reaction for dehydrogenation of alkanes in said dehydrogenation zone, (b) introducing a feedstream of said alkanes into said dehydrogenation zone in an amount sufficient to maintain hot withdrawn catalyst in a state of fluidization in said catalyst cooler, said state of fluidization existing in a sub-transport regime operating at a weight hourly space velocity WHSV of said lower alkanes not to exceed 5 hr -1 while maintained at a temperature high enough to convert at least 50% of said alkanes, and concurrently to cool said catalyst, (c) transporting cooled catalyst directly from said dehydrogenation zone, said catalyst now at a temperature in the range from about 1100°-1350° F. (649°-731° C.), to said regeneration zone, and mixing hot catalyst therein with said cooled catalyst, and, (d) withdrawing products of dehydrogenation in an effluent stream from said catalyst cooler.