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Fery
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Quote: Originally posted by MrDoctor  |
How well does that work, like, does it seperate well enough for use in a dean stark trap? and also, how strong is the azeotrope? how dry can you get
it this way? benzene and toluene are known to function as well as most primary dessicants, ethyl acetate is such a clean, non toxic chemical, which
has a lower boiling azeotrope than toluene, i wonder why i dont see it used more often? |
https://demonstrations.wolfram.com/SeparationOfAceticAcidFro...
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Deo
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Very interesting...
I cannot buy ethyl acetate for cheap - although neither can I buy toluene but at least I can get a decent amount through some elbow grease and
distillation of gasoline - Ethyl acetate would require me to do an esterification with... glacial acetic acid ... so that is quite circular.
Although it seems to me that methyl acetate would work too would it not? I can get that from acetone free nail polish removers from CVS and whatnot so
perhaps I will try with that instead...
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MrDoctor
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awsome, im looking at this data and finding it problematic that the output is a constant volume though, so i still cant figure out if a dean stark
trap would be effective or not. the ethyl acetate had been pretty much eliminated around 95%. Its also strange that the amount of ethyl acetate
present drops below the water content, yet water continues to leave at around the same rate rather than the distillate staying the same as solution. I
can kind of guess whats happening, if this is a parametric fit equation to actual data, but in practice one would not keep the rate of boiling so hard
1/6th of the acetic acid ends up being removed (unless you had to because water and ethyl acetate needs to flush out of the column), and also, i
think, though im not super sure, that if ethyl acetate levels remained high, being replenished thanks to the overflow of the dean stark trap, the
profile of the distillation would be very different, rather than what occured here which probably used the absolute minimum amount of ethyl acetate
capable of removing the volume of water present even though at the end a large amount of acetic acid has to distill over to flush the last 10% of the
azeotropic mixture out because theres no more ethyl acetate.
So i cant really imagine what the rate of water removal is like once there is virtually none. i would be hopeful that it more or less just leaves at a
fairly constant rate, so that you would have the entrainer refluxing fully at its boiling point with no acetic acid distilling over, and instead the
reaction is considered complete once acetic acid starts distilling over, and the last traces of the entrainer are leaving the system.
Also Deo, methyl acetate would probably work, i dont really see any reason why it wouldnt, although i have a feeling it will be somewhat reliant on a
packed reflux column that holds quite a bit of liquid soaked into it, at any given time.
lastly, you probably can get ethyl acetate for cheap. anywhere that gives a damn about environmental impacts of chemicals enough to haphazardly ban
things that barely have an impact anyway, will have a major hard-on for ethyl acetate since its such a universally good substitute for so many
solvents, including acetone which is fundamentally a petrochemical in origin.
look around some online stores that sell beauty products, they sell all sorts of whack stuff. nail brush cleaner or "saver" is usually acetone, ethyl
acetate or some nitroalkane, usually nitromethane. regular nail polish remover formulas tend to just be acetone or ethyl acetate, "acetone free" is
usually ethyl acetate, and infrequently i think MEK, but then "ketone free" is pretty much guaranteed to be ethyl acetate.
i bet at your local major hardware store there will be a dozen scattered products also labeled as brush cleaner, or some purpose-specific cleaning
solvent for roof painting, fiberglassing, grouting, etc, which is always pure acetone, IPA or EtAC.
but acetone-free nail polish remover or really just any product whatsoever that has "acetone-free" in its name, is probably EtAc.
And end of the day its not restricted so just buy some off amazon
[Edited on 15-10-2025 by MrDoctor]
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Deo
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| Quote: Originally posted by MrDoctor |
awsome, im looking at this data and finding it problematic that the output is a constant volume though, so i still cant figure out if a dean stark
trap would be effective or not. the ethyl acetate had been pretty much eliminated around 95%. Its also strange that the amount of ethyl acetate
present drops below the water content, yet water continues to leave at around the same rate rather than the distillate staying the same as solution. I
can kind of guess whats happening, if this is a parametric fit equation to actual data, but in practice one would not keep the rate of boiling so hard
1/6th of the acetic acid ends up being removed (unless you had to because water and ethyl acetate needs to flush out of the column), and also, i
think, though im not super sure, that if ethyl acetate levels remained high, being replenished thanks to the overflow of the dean stark trap, the
profile of the distillation would be very different, rather than what occured here which probably used the absolute minimum amount of ethyl acetate
capable of removing the volume of water present even though at the end a large amount of acetic acid has to distill over to flush the last 10% of the
azeotropic mixture out because theres no more ethyl acetate.
So i cant really imagine what the rate of water removal is like once there is virtually none. i would be hopeful that it more or less just leaves at a
fairly constant rate, so that you would have the entrainer refluxing fully at its boiling point with no acetic acid distilling over, and instead the
reaction is considered complete once acetic acid starts distilling over, and the last traces of the entrainer are leaving the system.
Also Deo, methyl acetate would probably work, i dont really see any reason why it wouldnt, although i have a feeling it will be somewhat reliant on a
packed reflux column that holds quite a bit of liquid soaked into it, at any given time.
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Apparently according to wikipedia ethyl acetate is immiscible with water? the upper organic layer would be about 90 ish percent EA and the lower water
layer is only about 8.7 % EA. So in a sense its just like toluene, but better at its job. Also I've come to realize that as a result, methyl acetate
wouldn't work because it IS miscible with water.
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MrDoctor
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with a dean stark? yeah it might not work. maybe. the solubility in water is 25% at rt and unspecified-higher when higher. So you would need to
determine how much methyl acetate it takes to remove X amount of water.
in the dean stark trap it might not have enough density difference due to solubility to seperate and recycle, but once outside the system, mixing it
with a brine of sodium chloride or something will cause seperation, but frankly you should just make sure you have enough to get the job done in one
go.
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Deo
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At the azeotrope temperature (56C) the % solutbility of MeOAc is about 70%. (According to LLE-calc)
At the azeotrope temperature (70C) the % solubility of EtOAC is about 59.4%.
So they are still immiscible to some extent, just that MeOAc will be much less efficient for removal via a Dean Stark, unless perhaps we cool the
trap? Seems kinda stupid.
I think in the simulation, it was assuming constant addition of EtOAc as it was depleted as it was deisgned for industrial processes, not a Dean-Stark
situation, so miscibility would not matter at all. However, with how cheap MeOAc is for me compared to EtOAc (I can get like 10oz crude in Walmart
Nail Polish Remover for $1.98), I might as well use it in the one pot method.
One thing I'm confused about is that the acetates seem to be extremely enriched in the vapor phase (91.9-95%), how does the water get removed so
quickly when we have basically less than 10% of the vapor being water? One would have to add an immense volume of acetate.
Toluene is seeming a lot more appealing again with these caveats...
[Edited on 15-10-2025 by Deo]
[Edited on 15-10-2025 by Deo]
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MrDoctor
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i might try this tomorrow with toluene after i clean up my work station, but starting from 90%
if it takes much longer than ethyl acetate is calculated to, then ill try it again with ethyl acetate as well.
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