Question
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Are catalyst additives available to boost bottoms processing in the FCC?
Nov-2021
Answers
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Lamma Khodeir, W. R. Grace & Co, Lamma.Khodeir@Grace.com
Increasing bottoms processing in the FCC will result in more undesirable slurry which means improved bottoms cracking is needed. Grace does offer additives that provide a boost to bottoms cracking. Such additives are typically applied when the base catalyst is not optimised for bottoms cracking performance and can have a quick impact on bottoms cracking performance. However, the more typical and recommended approach is to integrate the bottoms cracking functionality into the FCC catalyst itself, which avoids some potential negative impacts on yields associated with the additive approach, as subsequently described.
When using the additive approach for bottoms cracking, the large feed molecule diffuses into the separate additive particle and is subsequently cracked into intermediate products. These smaller molecules must then exit the additive before diffusing into the base catalyst particle where they are selectively cracked into more valuable FCC products. However, before the intermediate molecules can exit the additive they can undergo additional and less selective cracking reactions, resulting in higher amounts of coke and gas.
Other advantages of optimising the base catalyst for bottoms cracking vs using an additive approach include:
- Avoids the use of a separate additive injection facility, as well as the associated logistics.
- Bottoms cracking additives can dilute the base catalyst activity, resulting in higher daily catalyst additions and opex.
- Retention and fluidisation characteristics of the additive may differ from base catalyst.
- Slow activity decay rate of additives can result in a prolonged period where undesired selectivity shifts are observed.
- For catalysts incorporating integral metals trapping technology, contaminant feed metals are passivated, resulting in lower coke and gas make, unlike for additives which often contain no metals trapping functionality.For resid applications, hydrogen and coke selectivities cannot be neglected as these units are typically constrained by air blower rates, wet gas compressor, and/or maximum regenerator temperature. Additives might not be compatible with these constraints, leading to reduced conversion and/or feed rate and an overall loss in unit profitability.
Grace has a diverse and robust resid FCC catalysts portfolio to offer refiners with a highly customised catalyst to combine maximum bottoms conversion with optimum product yields. In addition, these catalysts incorporate state-of-the-art metals tolerance functionality, enabling refiners to process the most challenging feedstocks, unlocking significant operational flexibility and economic value.
Nov-2021
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