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I am currently looking at the mechanism of the formation of storage deposits in jet fuel. Interestingly, the concentration of acids in the fuel correlates strongly with the total insolubles formed over testing periods. As such, several papers propose acid catalysed deposition processes occurring. However, since jet fuel is a non-polar solvent, with very little water present, this would be an extremely slow process. Alternative, acids could be taking part in an alternate mechanism leading to deposits.

Currently I am employing DFT methods in my work to explore the deposition process from a mechanistic perspective. I represent the bulk jet fuel solvent with an n-dodecane PCM solvent model. N-dodecane was chosen as it is the average chain length of jet fuel bulk alkanes. To explore the protonation in these solvents with small amounts of dissolved water, I have been explicitly adding water molecules around the conjugate bases/acids and looking at how successive water molecules affect the ΔfG (Gibbs energy of reaction). However, I am unsatisfied with this method. At current I have been placing the water molecules at what seems like the most stable configurations. In fact there could be several stable configurations, and putting on calculations one-by-one in various configurations seems cumbersome and unsystematic.

Is there a more statistical approach to this problem? Or, would stepping outside of computational chemistry and performing a study in the lab be the only way to tackle this?

Thanks.

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  • $\begingroup$ I think that traces of water in apolar fluids can have non standard behaviour. Surely the activity a of protons must be very high. While a barrel can store water indefinitely, non anhydrous hydrocarbons or alogenated solvents can literally drill a hole through it. But I don't know the details. Just know that because of this a quick dessication is needed before storing alogenated wastes in big steel barrels. $\endgroup$
    – Alchimista
    Oct 29, 2020 at 7:47
  • $\begingroup$ Interesting, I will try and find any papers looking into this. $\endgroup$
    – Charlie A
    Oct 29, 2020 at 8:53

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