How can we raise butenes (butylenes) production from our FCC unit?
Response to a question in the Q1 2021 issues Q&A Feature
Melissa Clough Mastry
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This can be accomplished by operational changes, catalyst changes, or a mixture of the two. For catalyst changes, consider specialty catalysts (for example, Fourte and Fourtune), which increase butylenes preferentially by using a number of different features, including low hydrogen transfer index, the use of specialty framework topologies, an active matrix, and high activity. In multiple refinery trials, these technologies have delivered significant economic value, especially when butylenes are the highest priced product from the FCC. Another method to increase butylenes is the use of traditional olefin additives (based on ZSM-5 zeolites), however this will bring more propylene than butylenes, proportionally, so this is only recommended if the economics favour the total increase in LPG and if the additional propylene can be processed downstream the FCC. Finally, once the production of butylenes from the FCC reactor has been maximised, the next task will be to recover them as much as possible in the downstream of light ends separation system, so attention should go to the bottom section of the debutaniser tower where a significant amount of butylenes can be lost to the light naphtha.
It is also known that naphtha RVP specification changes in winter, allowing more C4s to be incorporated in the gasoline (greatly increasing the volume of gasoline sales) but it is advisable to lower the debutaniser bottom temperature on the atmospheric debutaniser tower (where C4s have no butylenes) than on the FCC debutaniser one.
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