Sciencemadness Discussion Board - Purifying of denaturated alcohol.

Purifying of denaturated alcohol.

Jaruj - 23-7-2015 at 22:58

Hi, I need help in separation of denaturated alcohol 95% from impurities. It contaiins denatonium benzoate (bitterant), gasoline and kerosene. I have an idea to distill it, but I get alcohol still contamined with gasoline and kerosene. Probably it is azeotrope.

So I have been thinking about some ways, to add some solvent, in that is soluble only ethanol or impurities (I mean solvent accesible for amateur chemist). Then simply separate layers. The send way is to mix that ethanol with water, it will form white emulsion, wait to settle the impurities, and it is done. But then next problem occurs as ethanol becomes contamined with water. Is it possible to obtain >98% ethanol? Could I use salt to dissolve in water to increase boiling point of water, to prevent azeotrope? Or add calcium oxide, or what? ???

Help me to solve this please!

(and sorry for my English, I am foreigner)

kecskesajt - 24-7-2015 at 04:27

Hmm maybe add 2x of it volume water(like 50 ml of alcohol to 100ml of water)and it will form a small layer.That will be gasoline and kerosine.Seperate it and then distill the alcohol from the water(3 times of distillation). After this,you could dry it with anhydrous potassium carbonate or cc. sulphuric acid.Do not use much,just 10ml of H2SO4 for 100ml of the 96% alcohol.You cant get denatonium benzoate out.

Jaruj - 24-7-2015 at 04:51

But when mixture will be distilled of, denatonium will not go with alcohol. It is salt, so why do you say I cant get out denatonium benzoate out? Or am I wrong?

karlos³ - 24-7-2015 at 07:08

You will get the bitrex(denatonium benzoate) out with distillation.
I would better invest your time and search for alcohol denatured with MEK and Bitrex, nothing else, usually 96% EtOH. Then you can distill with added NaOH, and after the second distillation (dry it after the first with NaOH/Na2SO4 mixture, or two separate times with each of them) you will get some pretty pure and dry alcohol, because the MEK will self-condense catalysed trough the NaOH in an aldol-additon/condensation, to a much higher boiling substance than MEK.
MEK has the same boiling point as EtOH, so its an usual denaturant here in my country.
Maybe you have access to such an denatured alcohol too?

kecskesajt - 24-7-2015 at 10:06

There is denatonium benzoate and saccharide.But is there free base denatunium?And if yes,does it has any taste?

ave369 - 25-7-2015 at 06:40

Denatonium is four times substituted ammonium. So, no free denatonium is possible, but there must be a denatonium hydroxide.

aga - 25-7-2015 at 09:38

It is far simpler to brew yourself some crude ethanol and then distill it with a 'thumper'.

dermolotov - 13-8-2015 at 13:11

Quote: Originally posted by aga

It is far simpler to brew yourself some crude ethanol and then distill it with a 'thumper'.

This is what I would recommend. Get some turboyeast for $20 a packet (the Rum quality one is what i use) and mix it with some potatoes, 8kg of sugar, and maybe a pineapple with 20L of water in a large metal garbage can for 2 weeks.
You can then distil that off to get around 3L of pure ethanol

Bot0nist - 13-8-2015 at 17:47

You say 3L of pure ethanol... I assume you mean the azeotrope, and even if so, what length fractionating column did you use? Did you have to do subsequent distillations of your distilate, and or any other drying methods to reach that concentration? In my experiance, even with a 30 cm insulated column, efficient condensor, and careful temperature and flow rate control, achieving 95% or greater ethyl alcohol is hard to achieve with a single distillation from ~20% or less feedstock, thumper or not.

careysub - 13-8-2015 at 18:14

Quote: Originally posted by Bot0nist

You say 3L of pure ethanol... I assume you mean the azeotrope, and even if so, what length fractionating column did you use? Did you have to do subsequent distillations of your distilate, and or any other drying methods to reach that concentration? In my experiance, even with a 30 cm insulated column, efficient condensor, and careful temperature and flow rate control, achieving 95% or greater ethyl alcohol is hard to achieve with a single distillation from ~20% or less feedstock, thumper or not.

For my money, I distill 40% ethanol bought fairly cheaply as vodka (higher proofs are available, but cost more per mL EtOH), then use potassium carbonate to salt it up to 94-95%, then use CaO or CuSO4 to dehydrate to ~99.5%, then use 3A sieves to get absolute (actually super dry) ethanol.

You can also dry it to 99.5% from 95% with KOH, but then you probably want to distill to remove the small amount of KOH that dissolves in the ethanol.

I live in California where 95% ethanol is not sold, but you can buy 75% Everclear. At a cost per mL that is about twice as much as the cheap vodka I can skip the distillation and just start with salting it out with K2CO3.

[Edited on 14-8-2015 by careysub]

dermolotov - 22-8-2015 at 08:49

Quote: Originally posted by Bot0nist

Yes, yes: not anhydrous. That would require much more than a simple moonshine still, glass or not.
Since the original question was to purify ethanol of the denaturing chemicals, that's why I posted a simple distillation.

If you wanted to dehydrate it further one can add in copious amounts of anhydrous copper sulphate and swirl+add more until you see white copper sulphate in the flask.

battoussai114 - 22-8-2015 at 10:11

Maybe molecular sieves? Denatonium Benzoate is a pretty big molecule, maybe you could try using something with small pore size to get rid of it while retaining the alcohol.

dermolotov - 22-8-2015 at 11:35

Quote: Originally posted by battoussai114

Maybe molecular sieves? Denatonium Benzoate is a pretty big molecule, maybe you could try using something with small pore size to get rid of it while retaining the alcohol.

you won't need sieves for that. just toss in some activated carbon and all is well.