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Author: Subject: Acetone distillation temp?
Fyndium
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[*] posted on 25-7-2020 at 03:53
Acetone distillation temp?


I think I should get back to basics for now, because I got a little confused. I've used to expect acetone is very easy to separate from water and other impurities, but now I have to ask this probably very beginner question.

When I was distilling wet acetone, it started to come over as usual at 56-58 and it stayed there for most of the part, but it slowly creeped up to 61-62 and at the end it raised to 70. So do I only collect the fraction that distills at 56-ish C? This would result in huge losses, because probably only half of the input acetone will distill at this temp. I suppose it should be ran under fractional reflux to get all water our?

I suspect that wet acetone might be the reason why my isomerization failed. If there is water present, it will go all wrong. I dried acetone with calcium sulfate prior and it did not clump, but it is somewhat hard to say because it always forms a mud.
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Fulmen
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[*] posted on 25-7-2020 at 04:27


Acetone shouldn't form any azeotrope with water (https://en.wikipedia.org/wiki/Azeotrope_tables), and the difference in BP should make it fairly easy to separate. A fractional column should improve yields though, as the pot concentration drops more water will come over. I would keep the 56-fraction as pure and keep the "tails" as a crude product for either re-distillation or non-critical use.

[Edited on 25-7-20 by Fulmen]




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Tsjerk
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[*] posted on 25-7-2020 at 04:36


How wet is wet? If it is in the 5-10% range you could dry the acetone with some epsom salt or so.
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Fyndium
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[*] posted on 25-7-2020 at 06:51


Wet in this instance is anything between 10 to over 50%, meaning the cetone is extracted from waterous residues or from a reaction that has water as one component.

I was thinking of getting or making as pure as possible acetone for isomerization and use crude for reactions that are not water sensitive.
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