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Refinery
Hazard to Others
Posts: 371
Registered: 17-2-2014
Member Is Offline
Mood: Still
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I don't know about this talk about impossibility of removing methanol via fractional distillation. People do that pretty much all the time with
moonshine reflux fractional stills and the possible methanol traces are called "foreshots" or "heads" which will come over first, hence the first
50-200ml is always discarded in distillations of 20-80 liters in size.
I find it hard to cross between different hobbies, when chemistry forums use small milliliter scale tabletop equipment and moonshiners can use 2-meter
high columns with 100l boilers for the same job. Sad thing is that it took me a tour to moonshiners forum to really understand fractional distillation
which is practically never done correctly at lab scale. Passive fractionation just does not work.
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Praxichys
International Hazard
Posts: 1063
Registered: 31-7-2013
Location: Detroit, Michigan, USA
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@ Refinery - what you say is true.
What the distillers are doing is removing a few fractions of a percent of methanol by discarding a large volume of the first EtOH/MeOH to come over.
Purifying denatured alcohol that contains somewhere between 15 and 40% MeOH is a different story. It will take many runs through very efficient packed
columns to achieve an acceptable separation. Further, there isn't a readily available way to check the concentration of methanol in the final product,
and therefore no good way to know if it's ready for drinking. It would only take a small error to end up with a dangerous amount of methanol in the
product.
You could do it with a 1-meter jacketed hempel column if you had the hours to sit there, and a gas chromatograph or HPLC to check that the separation
was sufficient to drink. At that point, you could have just bought a bunch of vodka a though, or purchased lab-grade ethanol. Hence, in the amateur
lab it is virtually impossible to separate the two, and I like to generalize it under "impossible" to avoid giving people the deadly idea that they
can just run it through a vigreux and drink it.
A great source of EtOH that nobody has mentioned is using the "MEK substitute" sold at most hardware stores in the US, which is 100% ethyl acetate.
Refluxing this with a strong base will create an acetate salt and pure ethanol, no separation of denaturants required.
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Refinery
Hazard to Others
Posts: 371
Registered: 17-2-2014
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Mood: Still
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For making feedstock ethanol for chemistry I think easiest way is to add 5-10g/L of NaOH into windshield washing ethanols, fractional distillate it to
azeotrope, filter it through activated carbon and redistill it. This would probably yield even drinkable alcohol and the input price varies between
3-5 bucks per liter at least where I live and it contains only ethanol, MEK, denatonium and detergents.
Just academic interest, but is there in theory any chemical reactions that reacts with benzene and/or aromatics but not with ethanol? Somewhere was
said that ozonation would yield ultra-neutral alcohol.
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unionised
International Hazard
Posts: 5102
Registered: 1-11-2003
Location: UK
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Imagine I buy some wine + drink it.
If there's any methanol in there, I drink that methanol- but it probably won't do me much harm (there's not much of it- it's less toxic in the
presence of ethanol and by comparison there's lots of fairly toxic ethanol).
Now imaging that, instead, I take that bottle of wine + run it through a still of some sort.
At worst, the still won't add any methanol.
So, as long as I take the trouble to be sure that (at least nearly) all the ethanol has distilled over I have a product that is no worse than drinking
the wine.
It would probably taste filthy- but that's a different problem.
Now imagine that I run the wine through a fairly good still and remove at least some of the low boiling fraction (acetaldehyde + methanol etc).
In terms of health effects, at least I'm drinking less methanol- along with my ethanol.
Just don't start from f***ing gasoline.
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