Sciencemadness Discussion Board

Your favourite ethanol cleanup?

DocX - 17-1-2022 at 10:16

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?

Fery - 17-1-2022 at 14:27

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]

Tsjerk - 17-1-2022 at 14:58

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]

j_sum1 - 17-1-2022 at 16:30

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. :)

Bedlasky - 17-1-2022 at 18:33

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.

DocX - 17-1-2022 at 23:07

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?


DocX - 17-1-2022 at 23:09

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!

Fery - 17-1-2022 at 23:26

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.

Fery - 17-1-2022 at 23:31

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/

DocX - 17-1-2022 at 23:34

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.

DocX - 17-1-2022 at 23:37

Quote: Originally posted by Fery  
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/


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?

Fery - 17-1-2022 at 23:52

Quote: Originally posted by DocX  
Quote: Originally posted by Fery  
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/


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?

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.

DocX - 18-1-2022 at 00:04

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 :D



[Edited on 20222222/1/18 by DocX]

a few opinions based on my efforts:

Sulaiman - 18-1-2022 at 00:09

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 :(

DocX - 18-1-2022 at 00:41

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 :(


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.

Sulaiman - 18-1-2022 at 00:52

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)

arkoma - 18-1-2022 at 16:53

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.

crow6283 - 18-1-2022 at 17:24

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.

Sulaiman - 19-1-2022 at 06:25

"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.

teodor - 20-1-2022 at 04:53

Quote: Originally posted by crow6283  
Reflux over CaO (must be dry!) for several hours


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.

Fery - 21-1-2022 at 02:02

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).

Chemgineer - 25-1-2022 at 14:23

DocX, have you tried Tomato Paste Wash?

https://birdwatchers.info/calculator/

Amos - 26-1-2022 at 06:28

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.

artemov - 28-1-2022 at 01:15

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.

Tsjerk - 28-1-2022 at 03:48

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.

artemov - 28-1-2022 at 04:21

Quote: Originally posted by Tsjerk  
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.


Maybe neutralize the hydroxide/ethoxide into a non volatile salt (sulfate?) first before distillation?

It seems CaCl2 (reputedly not suitable for drying lower alcohols) can break the ethanol-water azeotrope (Nishi 1975) ... I might try this, but only after I purify my ethanol. I have no use for absolute ethanol, yet, and I have no way of measuring the last few percentage of water in ethanol.

I have CaSO4, MgSO4, 3A MS, ...

Attachment: nishi1975.pdf (837kB)
This file has been downloaded 55 times

DocX - 3-2-2022 at 13:49

Quote: Originally posted by Chemgineer  
DocX, have you tried Tomato Paste Wash?

https://birdwatchers.info/calculator/


Um, no? But thanks!
Like I wrote, the spirit is already distilled and concentrated, using classic turbo yeast and sugar. And also, like I written multiple times, the object is NOT TO MAKE DRINKABLE BOOZE. I want to make a pure reagent. 100% ethanol, no lower or higher or secondary alcohols. So I just want to clean the stuff.

But can this tomato soup wash produce pure ethanol? Its not a lot of info in the link, just recipe. What exactly will the tomato paste achieve?

[Edited on 20222222/2/3 by DocX]

Amos - 4-2-2022 at 09:43

Tomatoes or tomato paste is a pretty common source of nutrients for the yeast, and I think it came out of the homebrewing community. They treat ethanol distillation like more of an art or alchemy than a science. While it may prove effective in getting a high yield of ethanol I doubt it's the best or purest among nutrient-rich plant matter. But it does underscore the importance of adding something to your ferment that mimics what the yeast are actually looking to feed on in nature.

SWIM - 4-2-2022 at 11:51

A previous thread on this subject included posts from Happyfooddance recommending that the mash should be rapidly distilled with no column before rectification to limit breakdown of materials and chemicals in the mash into volatile impurities which can pass over with the ethanol.

This worked well for me, but I was only doing it because I didn't have a large volume still that would take a rectifying column. Didn't know about the theory behind it till I read that post.

A falling film distillation apparatus might be Ideal here, but probably not worth the considerable price tag. Still, they are truly amazing at distilling a sample without subjecting it to prolonged heating.

Potassium carbonate draws water out of ethanol well enough that you get two layers and can separate the lower water/carbonate layer in a sep funnel. There are threads about this on here somewhere.
It doesn't give you anhydrous, but does give better than 95%.
This can be a real time saver if you're just working with a Vigreaux column 400mm long and a non refluxing distillation head, which is marginal for getting azeotropic distillate.

A Hempel with glass rings or helices or stainless steel SPP (spiral prismatic packing) gives a BIG reduction in theoretical plate height and makes it easy to get azeotropic ethanol in one go if you use a partial take-off head.
(There are even better manufactured packings from guys like Cannon industries, but they cost an awful lot)

One thing about trying to get very dry ethanol by distilling from CaO, or other drying agents: remember to dry that glassware! Dry it like you're setting up to make a grignard reagent.
Seemingly dry glass still holds a lot of water unless baked or torched, and your dry distillate may pick up water again from an insufficiently dried receiver flask.

Aw crap, I almost forgot to mention copper column packing. I haven't used this but a lot of distillers swear by it for neutralizing various impurities during distillation.
Maybe somebody who distills moonshine can chime in on this.
I know you're not distilling to drink, but moonshiners have a lot of tricks to deal with volatile impurities because they really screw up the flavor.

Edit: Most columns with discrete plates (Oldershaw, etc) are also great for distilling ethanol. Low plate high and high throughput potential.
But these are more expensive than jacketed Hempels and good packing, at least on the used glassware market.
Also, they aren't as widely applicable for distillation in general as most don't work under vacuum.


[Edited on 5-2-2022 by SWIM]