I accumulate a gallon or so of used ethyl acetate (contaminated with oils, resin and water) a month. I can certainly distill out the oils and resin
but how can i separate (break?) the water azeotrope? Calcium Chloride in the still?
Thanks for any advice.
Mike Meltonium - 20-10-2016 at 07:04
I would suggest first distilling and then adding a drying agent to it such as molecular sieves. Calcium chloride would work too, maybe, but some would
also dissolve into your ethyl acetate.mikeehlert - 20-10-2016 at 07:28
Wickipedia suggests a 4 Angstrom material for absorbing water such as the Zeolites. Anyone have any specific favorites? XeonTheMGPony - 20-10-2016 at 08:42
3A is used for water adsorption
I did mine with Anhydrous Magnesium sulfate
[Edited on 20-10-2016 by XeonTheMGPony]DJF90 - 20-10-2016 at 09:52
4A mol seives are suitable and routinely used. 3A is only required for drying of methanol, as MeOH molecules are able to fit within the 4A pores.
If you're sure there are no volatiles that'd pass over, a simple distillation will suffice. If water content is a problem, then further processing by
washing with saturated NaCl solution, drying over mag sulfate and distillation is suitable. If you require anhydrous EtOAc, then store over 4A mole
seives for at least a few hours (preferably overnight).aga - 20-10-2016 at 10:59
If you already got 4A that is.
I had some 4A and they didn't work well for ethanol.
If you gotta buy them, buy 3A.mikeehlert - 20-10-2016 at 12:07
DJF90 and aga:
Thanks for the feedback
I do want to be relatively sure it's close to anhydrous, say 99.5% pure. Can one expand on the virtues of the NaCl washing process vs running the
distillate over the sieves vs storing it over the sieves?
If this questions shows my total ignorance, yep I am.DJF90 - 20-10-2016 at 13:40
The brine washes will remove most of the water from ethyl acetate and subsequently allow use of smaller portions of dessicant. By this point I'd be
surprised if theres more than 0.5% (5000 ppm) residual water. Mol sieves will take up any traces water and likely leave you with less than 10 ppm.
Storing solvent over 10%w/v of activated sieves for a few hours (overnight is ideal) will typically achieve this result. From memory a few solvents
(MeOH, MeCN, THF) require significantly longer, but EtOAc is relatively easy.violet sin - 20-10-2016 at 20:18
Are the impurities(oil/resins) plant based or petrolium based? Not that it really maters, just curious. After a quick search, I can see why one
would ask. So many links for membrane technology, ethanol ternary azeotropes, junk and more junk. There were a few about breaking azeotropes with
ionic liquids, but I doubt that they would be easy to procure.
The above response seems quite reasonable by contrast.mikeehlert - 25-10-2016 at 12:38
Are the impurities(oil/resins) plant based or petrolium based? .
The oil is most likely petroleum based, the resin most likely plant based but really no way to be sure in either case.mikeehlert - 25-10-2016 at 12:45
Having gotten input from various sources, mostly from this board, I have a lot of trials to make.
in no particular order:
Straight distilled product (maybe the azeotrope doesn't matter)
3A Sieves
4A Sieves
Calcium Sulfate
Calcium Chloride
Magnesium Sulfate (Drierite)
I guess I'll try them all unless someone knows that one or more really don't work.
Thanks for all the help.
Mike unionised - 25-10-2016 at 13:04
LOL
Did none of you folk spot the obvious answer?
The azeotrope of ethyl acetate (EA) and water separates spontaneously into two layers when it cools and condenses.
The upper (EA rich) layer is 96.7% EA and the azeotrope is 91.9%.
So, you distil the stuff to get the azeotrope.
Let it settle and redistil the upper layer.
The azeotrope comes off first and carries away all the water.
Then pure EA distils over.
Next, redistil the original lower layer. That will give the azeotrope and leave water behind in the still pot.
You can throw that away.
So you now have some pure EA, some water and some of the azeotrope.
Let that settle and separate the layers. Distill them separately and so on.
With clever design you can set up a process to do the decanting and distilling continuously, rather than batch-wise.
LOL
Did none of you folk spot the obvious answer?
The azeotrope of ethyl acetate (EA) and water separates spontaneously into two layers when it cools and condenses.
The upper (EA rich) layer is 96.7% EA and the azeotrope is 91.9%.
Okay, I see what your saying. This will be useful. I'm probably not clever enough and don't have enough demand to justify the continuous setup to
replace the small batch still I have but will at least do/try the double distillation cycle and maybe then some driers on the product. Once again, a
learning experience. I love being a process engineer.mikeehlert - 26-10-2016 at 04:47
Sorry, this one is a bit over my head Cryolite. I've looked up the apparatus and understand how it works, pretty slick. Can certainly separate the
free water from the solvent/azeotrope. Do I understand that with further running the azeotrope will break and I'll end up with relatively pure EA or
do I need some sort of dryer in the boiling sump?
[Edited on 26-10-2016 by mikeehlert]mikeehlert - 27-10-2016 at 12:42
