Effect of feed properties on the optimization of FCC catalysts for bottoms reduction

A common operating goal of the FCCU is to maximize conversion of feedstock to products boiling below approximately 700/sup 0/F (-- 370/sup 0/C). The remainder (the so called ''bottoms'') is usually of low value compared to either the feed or converted products. Minimizing these bottoms requires matching the feedstock with the proper catalyst and being able to achieve the necessary operating conditions. Any changes in a particular feedstock-catalyst combination can significantly affect how a FCCU will perform within its own particular constraints. In this paper the authors first explore the yield and selectivity effects that could occur in an unconstrained FCCU as a result of systematic changes in catalyst properties for different feedstocks. However since commercial FCCUs always operate with many constraints (heat balance, economic, temperature, blower, etc.) the authors demonstrate how the combination of various unit operational limits and feedstock properties can dictate how catalyst properties must be optimized to provide maximum bottoms reduction.