Evaluation of Coke Selectivity of Fluid Catalytic Cracking Catalysts

In resid cracking the high feed metals and Conradson Carbon Residue (CCR) require careful consideration when assessing both catalyst design and performance evaluation. This paper addresses the issues of the latter with respect to coke, delta coke and catalyst deactivation. Overall, evaluation of catalysts on resid feedstocks requires sophisticated and well integrated catalyst deactivation, catalyst stripping and cracking systems. It is important to determine not only the coke yield, but each of its components (Catalytic coke, contaminant coke, CCR coke and stripper (soft) coke). This paper provides details on how each of the components of the coke yield may be experimentally determined using catalyst metallation by cyclic deactivation, catalyst strippability measurements and modified catalytic cracking techniques. In fixed-bed catalytic cracking tests the proper decreasing delta coke response as catalyst-to-oil is increased is possible if a constant catalyst load and a constant feed injection rate are maintained. As CCR increases above 4 wt%, however, fixed-bed cracking methods are suspect because the mass balance drops significantly and the cracking performance can be measured better using other techniques (e.g.s., circulating pilot plants or fluidized-bed reactors).