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DocX
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Your favourite ethanol cleanup?
So I'm in the process of stacking up my lab with the fundamental pure reagents and solvents, as is probably apparent from my many posts.
Now I've come to the ethanol.
I have chosen the long path out of curiosity, and I brewed a sugar wash and have distilled quite a few liters of 95% ethanol this way, using glassware
and a vigreux column in the final step. I used potassium permanganate in one of the cleanups to oxidize some of the byproducts.
Still though, my final product tastes like crap.
I don't mind the taste, I'm not doing this to drink it, but I want really pure anhydrous ethanol for use as a reagent.
What are your favorite methods for getting rid of all the leftover secondary or tertiary alcohols that can still be present? NaOH? Dilution and
activated charcoal, followed by redistillation to 95%? Carbonates?
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Fery
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KMnO4 oxidizes also 95% ethanol. As ethanol was in big excess in comparison with byproducts you probably oxidized only very little of byproducts and a
lot of ethanol.
I try to substitute anhydrous ethanol with commercial methanol or isopropanol whenever possible as they are much more cheaper (no extra tax applied
for undrinkable alcohols). Methanol as well isopropanol are free of shits like methylethylketone and denatonium benzoate used in denatured ethanol.
I purify commercial denatured azeotropic ethanol by sitting over NaOH and refluxing (aldol condensation of MEK), then simple distillation.
I prepared very pure pharma / food grade ethanol by fermenting apples with sugar and column distillation (apples were there just as a source of
nutrients and source of yeast)
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...
https://www.youtube.com/watch?v=0wMHckg64iA
Dehydratation of azeotropic ethanol could be done with adding entrainer to form ternary azeotrope (e.g. benzene or hexane) and then molecular sieves
3A to remove the remaining water.
IIRC I read somewhere in the sciencemadness forum that KMnO4 could be used to determine whether ethanol is really without traces of water, then it
should not dissolve in ethanol at all. If traces of water they you immediately see the familiar color of permanganate.
[Edited on 17-1-2022 by Fery]
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Tsjerk
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I would just get some cheap denatured azeotropic ethanol, reflux with NaOH. Dry with MgSO4 and discard the first and last 10% when distilling. Store
over sieves.
Did you discard any for runs when distilling? Otherwise I wouldn't know how it can still taste bad after distilling it to 95%.
Better even buy 99% bioethanol sold for decorative fire places / camp stoves. Reflux with NaOH, distill of the first 50%, which will be about 98%
ethanol, the rest will be nearly anhydrous.
https://www.oliedirect.nl/product/bio-ethanol-99/
Azeotropes work in two ways, you can't get ethanol from water at any concentration higher than 96%, but you will also first distill 96% ethanol from a
solution that contains more than 96% ethanol. Meaning you will dry the remainder in the flask when distilling 99% ethanol.
[Edited on 17-1-2022 by Tsjerk]
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j_sum1
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Most of the ethanol I use is very discoloured and contains a very large amount of water and a wide range of other impurities. And it tastes delicious.
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Bedlasky
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DocX: You can send me small sample and I can do GC analysis and water content on KF if you want. But ethanol from sugar should be quite pure, look to
Fery's thread. I did GC analysis for him and his ethanol contained <0,1% MeOH, <0,03% of higher alcohols (there were 4 of them - n-propanol,
isobutyl alcohol, isoamyl alcohol and one unknown alcohol, probably some branched hexanol) and <0,005% ethyl acetate.
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DocX
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Quote: Originally posted by Tsjerk  | I would just get some cheap denatured azeotropic ethanol, reflux with NaOH. Dry with MgSO4 and discard the first and last 10% when distilling. Store
over sieves.
Did you discard any for runs when distilling? Otherwise I wouldn't know how it can still taste bad after distilling it to 95%.
Better even buy 99% bioethanol sold for decorative fire places / camp stoves. Reflux with NaOH, distill of the first 50%, which will be about 98%
ethanol, the rest will be nearly anhydrous.
[Edited on 17-1-2022 by Tsjerk] |
Thanks! Yes, I distilled it by the book, discarding foreshots, heads and tails. Still, it tastes like paint thinner. I tried one run with
KMnO4 and one without, and the one with definately tasted better.
Naturally, I would love to use my own alcohol, but I'd happily buy some Smirnoff (or whatever) and have a go with that if that would give me a cleaner
end product? But as I understand it drinking alcohol is full of heavier alcohols to give it character?
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DocX
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| Quote: Originally posted by Bedlasky | | DocX: You can send me small sample and I can do GC analysis and water content on KF if you want. But ethanol from sugar should be quite pure, look to
Fery's thread. I did GC analysis for him and his ethanol contained <0,1% MeOH, <0,03% of higher alcohols (there were 4 of them - n-propanol,
isobutyl alcohol, isoamyl alcohol and one unknown alcohol, probably some branched hexanol) and <0,005% ethyl acetate. |
Great! I'll do that as soon as my cleanup process is done. Thank you!
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Fery
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I must definitely suggest Bedlasky. He was very helpful in GC, not only ethanol but also 2-nitrotoluene.
I have to emphasize that I used very powerful 1 meter long 3 cm inner diameter Hempel column packed with small Raschig rings. Variable reflux rate
distillation head. Powerful heating mantle (reflux flow was more than approximately 20 drops per second, it could not be calculated more precisive due
to very high reflux flow). Using Vigreux column and without variable reflux rate distillation head I couldn't achieve such purity. For fermentation I
used only apples and grocery white sugar (made from sugar beet) to introduce as little of contaminants as possible.
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Fery
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DocX when you drink beverages with ethyl alcohol, it is metabolized to acetaldehyde in first step. What do you think acetaldehyde does with liver
cells, especially with DNA?
https://pubmed.ncbi.nlm.nih.gov/16054980/
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DocX
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And just to be clear once more: I will use the end product as a reagent, not as a solvent. I will make diethyl ether, chloroform and chloral hydrate.
So I want the starting material to be as pure as possible.
Final dehydration will be performed with 3A molecular sieves.
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DocX
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Ummm ... ok? Yes, I am very aware of the health effects of alcohol and other drugs. I fail to see why it's relevant in this discussion though?
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Fery
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| Quote: Originally posted by DocX |
Ummm ... ok? Yes, I am very aware of the health effects of alcohol and other drugs. I fail to see why it's relevant in this discussion though?
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Because of this:
| Quote: Originally posted by DocX | | Still, it tastes like paint thinner. I tried one run with KMnO4 and one without, and the one with definately tasted better. |
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DocX
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| Quote: Originally posted by Fery |
Because of this:
Still, it tastes like paint thinner. I tried one run with KMnO4 and one without, and the one with definitely tasted better. |
Because I tasted a little alcohol? You imagine that would give me hepatocarcinoma? Awwwww ... You don't have to worry about that, I'll be fine .
And like I said, I won't be using this for drinking. I don't drink alcohol, in fact. Sometimes, though, I taste it 
[Edited on 20222222/1/18 by DocX]
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Sulaiman
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a few opinions based on my efforts:
| Quote: Originally posted by DocX | ... So I want the starting material to be as pure as possible.
Final dehydration will be performed with 3A molecular sieves. |
Treat your yeast kindly,
. don't go for very high (>10%) ABV fermentations,
. temperature, pH, aeration, nutrients can significantly affect product purity
so more time and more heat for the stripping run is the cost of 'purity'
3A sieves are great but they adsorb an awful lot of your product if you (I) try to go from near azeotropic to anhydrous.
(even worse if I use cheap 3A sieves that also have 4A pores 
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DocX
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| Quote: Originally posted by Sulaiman | | Quote: Originally posted by DocX | ... So I want the starting material to be as pure as possible.
Final dehydration will be performed with 3A molecular sieves. |
Treat your yeast kindly,
. don't go for very high (>10%) ABV fermentations,
. temperature, pH, aeration, nutrients can significantly affect product purity
so more time and more heat for the stripping run is the cost of 'purity'
3A sieves are great but they adsorb an awful lot of your product if you (I) try to go from near azeotropic to anhydrous.
(even worse if I use cheap 3A sieves that also have 4A pores
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Ok. Yield is not a big issue, actually. Like I wrote I have liters of the stuff. Luckily, because my sieves are definitely the cheap kind.
Fermentation is already done though, so I have to work with what I got.
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Sulaiman
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My cheap 3A sieves were VERY dusty when I got them,
but ok after one use and then washed and dried and subsequently reused.
I suggest a water wash then drying before use to avoid this problem.
(if your sieves are also dusty)
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arkoma
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I have some *ahem* experience in this area. It's ALL IN THE YEAST. Bakers yeast=bad. Lots of crap, i.e. stinky shit.
Alcotec Vodka Turbo. 1 pack of yeast, 16 lbs sugar and 4 gallons of water usually net me 3 liters of 95% EtOH.
"We believe the knowledge and cultural heritage of mankind should be accessible to all people around the world, regardless of their wealth, social
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crow6283
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Reflux over CaO (must be dry!) for several hours then let the apparatus sit over night - make sure you using a drying tube. The next day distill.
Make sure you use a short column, splash proof still bead, or something else to make sure no CaO splashes over. Discard the first few milliliter.
Protect your receiving flask or distillation adapter with a drying tube. This will give you very dry ethanol if you ever need it.
I’ve distilled various liquors when I needed ethanol in a pinch. Rather than distilling a bit and discarding it I found that simply bringing it up
to a boil without the three way adapter in the joint and letting it run for several minutes was very effective at removing any taste from the final
product. Just let it go for a while then put it together fully so the vapor gets to condenser and you’re good to go. Of course this should be done
with proper ventilation no open flames blah blah blah.
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Sulaiman
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"heads & tails & smelly fractions"
is on the label of a bottle that I keep for various cleaning uses.
Safer to condense heads than release them, I think.
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teodor
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I used this method but I would not recommend it. I think the commercial CaO is rarely is pure. I bought my at S3 and it gave a "burned" smell to
ethanol.
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Fery
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CaO for dehydratation of ethanol is good enough technical 95% which is sold in 25-50 kg bags from shops supplying building industry. They sell hydrate
= Ca(OH)2 which could not be used for dehydratation and anhydrous CaO. I tried that once ago and it seems to substantially reduce yield, at the end it
was very difficult to distill the thick paste of ethanol + Ca(OH)2
Yes burned smell is undesirable when you want to prepare good scenting esters as Teodor wrote.
DocX I wanted to point you that oxidated products of alcohols (aldehydes) are much more toxic (plus you could oxidate anything else present in
ethanol). Tasting chemicals is commonly bad practice but I understand you because taste/scent is sometimes more sensitive than gas chromatography,
just tongue/nose can't give you exact number to calculate concentration like output of gas chromatography. When you have extra glass used only for
pharma/food grade ethanol distillation made from fermentation process this is good source of your own pure pharma/food alcohol but I wouldn't purify
that alcohol by any oxidation reagent. Alcohol purified by oxidation could be suitable for chemistry although I'm not sure whether oxidation purifies
ethanol or introduces more contaminants (it could be purification but also dirtying). Personally I would just distill on efficient column. But if
improper fermentation I can imagine that the column distillation won't be able to get rid of some bad smell. I know that some people drinking home
made distilled alcohol try to purify it using pharma/food grade medicinal charcoal, but I only read about that, never tried.
Also prepare to some loses of alcohol if you need anhydrous.
1 year ago I was very satisfied with this purification:
https://www.youtube.com/watch?v=0wMHckg64iA
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...
I was surprised how sharp was the separation and how quickly the temperature raised on different fractions in few seconds (I separated forerun circa
100 ml from which 25-50 ml was really forerun and the rest was removed just to be more pure, main fraction circa 2 L and tail circa 100 ml).
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Chemgineer
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DocX, have you tried Tomato Paste Wash?
https://birdwatchers.info/calculator/
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Amos
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Turbo yeast will always produce a product that tastes and smells foul, as the yeast or its cellular debris will always make it into the distillation
setup without fail as they can't be settled or filtered out. If you want a proper neutral spirit go for a large fermentation size and low final ABV,
with something more naturally developed like bread yeast. And keep your yeast happy and nourished, as someone else already said.
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artemov
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I have some ethanol distilled once directly from a diethyl malonate synthesis sitting over some calcium sulfate.
I doubt it is even azeo ethanol, and probably not pure.
I am trying to clean it to get ethanol (as pure as possible) again.
How do you clean/dry ethanol with NaOH (or KOH)?
As in how much to add? Do I let it sit for a few days, or reflux immediately? How long to reflux?
Wouldn't hot NaOH eat glassware?
Cheers.
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Tsjerk
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I wouldn't use brand new glassware when boiling hydroxide in ethanol, it will etch the glass a bit, making it look dull.
I don't how NaOH or KOH would dry ethanol as it dissolves, maybe it breaks the azeotrope? I would use something like MgSO4 or CaO. Na2SO4 can be used
but then filter before distilling, as it loses water at low temperature already.
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