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Naptha containing 2% cyclohexane

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someonesomehere

Rising Star
Greetings!

I've got my hands on some cleanly evaporating solvent and happy about finding one. The problem is however the 2% cyclohexane... Or is it?

I've been snooping around and found that cyclohexane is garbage at freeze precipitating because of it's low freezing/melting point (6C).

So my questions are:

1. Would this however be a problem when it only has a content of 2%?
2. Is there a way I can separate the cyclohexane from the naptha?
3. I tried freezing the solution on it's own hoping the cyclohexane would become solid, but it didn't! How come it stayed liquid even though it's freezing point is way above the temperature in the freezer?

Thank you greatly for your input. ;)
 
Put the naphtha in the freezer, set on its lowest setting. If cyclohexane crystallizes out, decant off the liquid and repeat the process. If it doesn't crystallise, it would still be prudent to run a sample of any freeze-precipitated DMT from this solvent through a mini A/B. If oily material separates after dissolving in acid, put it in the fridge - cyclohexane will solidify (if your fridge is cold enough) and we would then know that it co-crystallizes with, or gets occluded by, DMT.

It's rather more likely that there will only be enough cyclohexane present to make an oily smear on the surface in which case you might want to try (carefully) familiarising yourself with its odour. Rather than running the whole batch through a mini A/B, dissolving in acetone and leaving to evaporate will clean things up, especially if repeated a couple of times. I'd also check the miscibility of acetone with cyclohexane, perhaps.
 
downwardsfromzero said:
Put the naphtha in the freezer, set on its lowest setting. If cyclohexane crystallizes out, decant off the liquid and repeat the process. If it doesn't crystallise, it would still be prudent to run a sample of any freeze-precipitated DMT from this solvent through a mini A/B. If oily material separates after dissolving in acid, put it in the fridge - cyclohexane will solidify (if your fridge is cold enough) and we would then know that it co-crystallizes with, or gets occluded by, DMT.

It's rather more likely that there will only be enough cyclohexane present to make an oily smear on the surface in which case you might want to try (carefully) familiarising yourself with its odour. Rather than running the whole batch through a mini A/B, dissolving in acetone and leaving to evaporate will clean things up, especially if repeated a couple of times. I'd also check the miscibility of acetone with cyclohexane, perhaps.
Click to expand...

That's a really smart way to test it! :lol:

Yea i tried freezing it but to no avail, and I wonder what the reason could be? I hoped it would be an easy solution.

I have not yet done a mini A/B so forgive me for my ignorance.
IF they turn out to have co-crystallized will doing that mini A/B seperate the two, DMT staying in the vinegar and the cyclohexane floating on top? (am I allowed to just chuck the crystals into the vinegar without dissolving it in solvent first?)

Should it not be possible to melt the DMT, letting the cyclohexane evaporate off in the process?

I checked miscibility and from the charts I found it seems they are miscible, so if it comes to it I'll do that acetone clean-up!
 
I just noticed that cyclohexane's azeotrope with methanol, with a boiling point of 45.2°C would be a potentially useful way of removing cyclohexane from mixtures - albeit it one that uses a more toxic solvent! As far as using methanol to separate c-hex from naphtha, that could get messy since various alkanes form azeotropes with methanol too and, while the n-alkane azeotropes have a reasonable (~15°C+) separation from that of the c-hex one, I haven't seen any data for branched-chain alkanes.

It might be a fun experiment to see if you could remove the c-hex from the naphtha this way, if you happened to have some MeOH and the requisite equipment and chemistry experience. I also wonder if the c-hex crystallises out of MeOH by freezing. (Tbh, I doubt it and anyhow, it forms two phases.)

Further comments here.
 
downwardsfromzero said:
I just noticed that cyclohexane's azeotrope with methanol, with a boiling point of 45.2°C would be a potentially useful way of removing cyclohexane from mixtures - albeit it one that uses a more toxic solvent! As far as using methanol to separate c-hex from naphtha, that could get messy since various alkanes form azeotropes with methanol too and, while the n-alkane azeotropes have a reasonable (~15°C+) separation from that of the c-hex one, I haven't seen any data for branched-chain alkanes.

It might be a fun experiment to see if you could remove the c-hex from the naphtha this way, if you happened to have some MeOH and the requisite equipment and chemistry experience. I also wonder if the c-hex crystallises out of MeOH by freezing. (Tbh, I doubt it and anyhow, it forms two phases.)

Further comments here.
Click to expand...

Thank you for the update! Knowledge is power :D
 
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