Question
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Are catalyst additives available to boost bottoms processing in the FCC?
Nov-2021
Answers
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Jarred Drewry, Johnson Matthey USA, jarred.drewry@matthey.com
Yes, there are multiple approaches to increase bottoms processing in the FCC with additives. With heavier feed in the unit, the base fresh catalyst may lack sufficient matrix activity to crack the larger feed compounds, resulting in lower conversion and higher slurry yields. In this situation, a high matrix additive, such as Johnson Matthey’s BCA-105, can provide additional matrix activity, allowing for cracking of the heavy components with reduced slurry production. BCA-105 reduces bottoms yield through easing of reaction pathways. It pre-cracks feed into LCO boiling range material, but the final yield structure of converted material is primarily determined by the properties of the catalyst system in terms of MAT activity (F-cat adds), hydrogen-transfer opportunities, and presence of ZSM-5. For instance, if BCA-105 is added on top of the main catalyst, higher MAT activity will lead to higher conversion and higher gasoline selectivity; if BCA-105 is added replacing part of the main catalyst, the selectivity will lead to LCO maximisation (see Figure 1), and finally the conversion to LPG would be influenced by ZSM-5 present in the system.
Additionally, increased bottoms processing will likely introduce higher metals to the unit which poison the base catalyst. These poisons, along with the heavier feed, will result in reduced yields and higher delta coke which can then cause process constraints such as regenerator temperature limits. In this situation, a proven metals-trapping additive, such as Johnson Matthey’s Cat-Aid, can mitigate the impacts of poisons while decreasing delta coke, resulting in lower regenerator temperatures. This additive approach for metals control will also increase conversion while reducing slurry. In any case, the advantage of this approach is that an additive can be started and stopped as needed, depending on the feed. This allows the refiner to maintain its standard fresh catalyst blend while being able to quickly shift to additional bottoms processing.
Nov-2021
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