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

摘要

Lower alkanes are converted to olefins in a 'third bed' external catalyst cooler (ECC) in which hot catalyst, from the regenerator ('second bed') operating in conjunction with a fluid catalytic cracker ('first bed'), thermally cracks and dehydrogenates the alkanes. Because this is an endothermic reaction, the catalyst is autogeneously cooled before it is recirculated to the FCC regenerator. The cracking catalyst is the catalyst of choice in the FCC reactor. The most evident benefit of using the ECC is that it eliminates internal regenerator coils for steam regeneration. Among several additional benefits is that the ECC allows flexibility in design of its fluid 'third bed' for optimum weight hourly space velocity (WHSV), and control of the dehydrogenation temperature so as to get maximum conversion of alkanes. This conversion can be maintained because the FCC regenerator burns the coke made during alkane dehydrogenation. The ECC also permits control of the temperature at which the FCC regenerator operates so as to facilitate processing heavier than conventionally used feedstock in the FCC unit resulting in better earnings.