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ZIGZIGLAR
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Purification of denatured ethanol
Hi. I'm exploring cost effective means for preparing absolute ethanol for reactions without creating the rectified spirits myself (as this is
considered moonshining and is illegal in my state).
Ironically, it seems the best option is purifying methylated/denatured spirits, as the cost per ml of the contained ethanol is extremely low as it
bypasses the alcohol beverage tax laws here.
I have been reading Practical Organic Chemistry (pages 136-137) and Purification of Laboratory Chemicals (pages 166-170) and understand the processes
described, however, I'm not clear as to which of them is appropriate in the comprehensive reliable separation of ethanol from methanol and other
denaturing or bittering agents.
Can anyone clarify this for me? Many thanks in anticipation. Cheers
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TheChemiKid
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First off, this should have been posted in Beginnings.
UTFSE! Denatured alcohol can be fractionally distilled over activated carbon and sodium hydroxide. This may need to be repeated several times.
When the police come
\( * O * )/ ̿̿ ̿̿ ̿'̿'̵͇̿̿з=༼ ▀̿̿Ĺ̯̿̿▀̿ ̿ ༽
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ZIGZIGLAR
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Thanks, TheChemiKid. I'd never seen the abbreviation UTFSE before haha I have read through several threads resulting from my search efforts before
posting. My apologies if I missed some relevant threads ... I'll try some new search parameters and see what they yield.
Looks like I may have been on a dead trail with the two books then, as there is no mention of this method as far as I recall. Many thanks for your
assistance.
Cheers
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subsecret
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Remember that the methanol (bp: 65 C) has a lower boiling point than the ethanol (bp: 78 C), so remember to swap collection vessels after the methanol
fraction has been purged from the apparatus. Bittering agents are usually large, higher-boiling organic molecules, so don't worry about carrying any
of these over.
Fear is what you get when caution wasn't enough.
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ZIGZIGLAR
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Thanks, Awesomeness. I have a multi-fraction collection Cow to separate distillate fractions.
I re-searched the forum and read a number of threads and as far as I can tell, there appears to be a lot of theoretical debate on the reliability and
comprehensiveness of any known method.
For many reactions, trace amounts of denaturants are of no consequence, but for others they are. If there was a method of proven conclusive
separation, I'd prefer to use it so that the reagent is more versatile.
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bfesser
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Thread Moved
3-2-2014 at 16:58 |
TheChemiKid
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Just so you know, here at sciencemadness UTFSE is somewhat of a joke.
It is officially Use the Forum Search Engine, but many people think of it as Use the F***ing Search Engine 
When the police come
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ZIGZIGLAR
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Quote: Originally posted by TheChemiKid  | First off, this should have been posted in Beginnings.
UTFSE! Denatured alcohol can be fractionally distilled over activated carbon and sodium hydroxide. This may need to be repeated several times.
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When you say to distill it over activated carbon and sodium hydroxide, do you mean to introduce these to the boiling flask?
Oh I interpreted the abbreviation with the F*ing meaning, 
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TheChemiKid
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Yes I do mean introduce these into the boiling flask.
When the police come
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ZIGZIGLAR
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Thanks, I shall give it a go. However, I'm not sure how I can test for the possible denaturants. No manufacturer lists the specific denaturant/s or
bittering agents, because they are not required to do so if they represent less than 1%.
Possible denaturants include but are not limited to: diethyl phthalate, tertiary butyl alcohol, brucine sulphate, denatonium benzoate, methyl isobutyl
ketone, and fluorescein.
:/ any advice? What is your experience treating a denatured spirit with this method?
Would your method elliminate the denaturates in the following composition? (I found one that lists the denaturants):
NAME CAS RN %
ethanol 64-17-5 >95
methyl isobutyl ketone 108-10-1 0.25 ^
denatonium benzoate at 6.6 ppm
denatonium benzoate 3734-33-6 0.00066
fluorescein 0.0001
brucine sulfate 4845-99-2 Not spec^
water 7732-18-5 Balance
[Edited on 4-2-2014 by ZIGZIGLAR]
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Bot0nist
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By the time you get a suitable fraction that is free of denaturants and then go about drying it you will have invested a fair bit of time and energy.
Why not start with 95% food grade ethanol (aka everclear or goldengrain liquor). It is more expensive, but then you can just proceed to the drying
step.
Good luck, and welcome.
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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Turner
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Do you want to drink the ethanol that you are purifying?
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ZIGZIGLAR
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| Quote: Originally posted by Bot0nist | By the time you get a suitable fraction that is free of denaturants and then go about drying it you will have invested a fair bit of time and energy.
Why not start with 95% food grade ethanol (aka everclear or goldengrain liquor). It is more expensive, but then you can just proceed to the drying
step.
Good luck, and welcome. |
We don't get everclear here. The closest equivalent here is named Spirytus (self explanatory) and is $60 per 500ml. As such, I'm willing to invest a
bit of time to produce my own!
The temptation to produce my own rectified spirits is increasing, but I will first continue to explore the possibility of using cheap household
denatured ethanol. With the assistance of this forum
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ZIGZIGLAR
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Let's just say yes as I've already learnt how to extract a solution from denatured alcohol that adequately serves as an ethanol reagant for most
reactions, but one of the main reasons I'm wanting to comprehensively elliminate all denaturants is because I may use it as a solvent in the process
of making other consumables or topicals. (My wife employs my lab to further her own obsession with health and beauty.)
I won't actually drinking it (I prefer beer, if anything). I could invest in laboratory absolute ethanol and simply collect the distillate to stretch
it out a while, but why not produce it cheaply if I can?
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Bot0nist
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Sorry, I assumed you were in the states. Im sorry. I personally use the everclear as a solvent and its not to pricy here. Anyways, good luck agian
friend. Keep that attitude of gratitude, lol.
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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Crowfjord
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I like to use Kleen Strip green denatured alcohol (green as in environmentally friendly); it is denatured only with small amounts of methanol, methyl
isobutyl ketone and ethyl acetate. Do you have something similar where you live? I haven't tried yet, but I figure that one could make it fairly pure
by distilling over sodium hydroxide, followed by a couple distillations. The ethyl acetate should cleave to ethanol and sodium acetate (or
polymerize), and the ketones should polymerize and stay in the boiling flask, leaving you with methanol as the main impurity to deal with. I'm not
sure how denatonium would behave under these conditions. Stevens or Sommelet rearrangement?
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Bot0nist
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What size fractionating column are you using?
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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ZIGZIGLAR
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I assume you're asking Crowfjord, but just in case you're asking me: the largest column I have is #24 400mm jacket length Vigreux. I have a smaller
Hempel I could pack to probably achieve more theoretical plates though.
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Fantasma4500
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methanol should react with Al2O3, which ive read alot about should be the main contaminant of denatured alcohol, however if you have found something
stating that no methanol is added then you wouldnt be able to make aluminium methoxide from reacting the denatured alcohol with aluminium foil (in
which has Al2O3 coating) followed by fractionally distilling it
denatonium benzoate remains after destillation as a solid that im not entire sure if i decided to taste, could be my mind totally just shut off the
memory if i did?
i just used rubber plug with PVC hose to distill it, also you could potentially salt out other components, like water.. not sure if theres any limit
to salting out's efficiency
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hyfalcon
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Salting out is not going to work. Not to break the azotrope of ethanol anyway. I would distill 3 times then take what came over the third time and
fill my Hempel column with 3A molecular sieves and distill again. This should break your azotrope and get you where you want to be.
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ZIGZIGLAR
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The Denatured Spirits I found hasn't even got any methanol in it, strangely.
The denaturants have high boiling points. Unless any of them form azeotropes, shouldn't a simple distillation, carefully ceased as the temperature
rises above 78~ be enough?
methyl isobutyl ketone : 117 bp
Methyl isobutyl ketone: ORAL (LD50): Acute: 1600 mg/kg [Guinea pig]. 2671 mg/kg
[Mouse]. 2080 mg/kg [Rat]. DERMAL (LD50): Acute: 20001 mg/kg [Rabbit]. VAPOR (LC50): Acute: 8000 ppm 4 hour(s) [Rat].
denatonium benzoate :163 ish bp
Denatonium benzoate: ORAL (LD50): Acute: 584 mg/kg [Rat].
fluorescein: 626c
No know health effects
brucine sulfate : 630bp
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ZIGZIGLAR
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| Quote: Originally posted by hyfalcon | | Salting out is not going to work. Not to break the azotrope of ethanol anyway. I would distill 3 times then take what came over the third time and
fill my Hempel column with 3A molecular sieves and distill again. This should break your azotrope and get you where you want to be.
|
Refluxing the 95.6% ethanol/water azeotrope over anhydrous CaO is one of the most widely published methods of breaking the azeotrope to create the
typical dry "absolute" 99.5% solution. I don't see why the this wouldn't work over 3A sieves, but I also don't see why packing a Hempel with them
wouldn't work either.
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subsecret
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I've also heard of Crown "Next" denatured alcohol, which contains 90% ethanol and 10% isopropanol. Ethanol boils at about 78.4 C, and isopropanol
boils at 82.5 C, and that's only a ~4 degree difference. Those would be rather hard to separate, even with a very good fractionating column. I haven't
been able to find any in my local hardware stores, but try to see if yours provide it. Perhaps you could custom build a fractionating column by
driving a long length of 1/2 inch copper tubing through a rubber stopper , and then sticking this into the neck of a flask. Adjust the size of the
column as you wish, and add insulation if your column proves to be too much of an obstacle for the vapors. The other end of the copper pipe could be
joined to a stillhead in a similar manner, or if you know how to solder, a turn could be made and the pipe could be fitted to a condenser with another
stopper. (In the US, so-called "soft copper" pipe is available, and it can be bent more easily, provided you have a pipe-bending spring to slide over
the section to be bent).The latter method could carry impurities from the copper into the ethanol, so a second distillation could be conducted, after
the ethanol is dried. Chances are that you'd still have isopropanol in the distillate, but this volume would be significantly reduced be the long
column.
As far as I know, this method has not been tested, and may not work as well as I think it will.
Fear is what you get when caution wasn't enough.
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ZIGZIGLAR
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Step 1. Add carefully concentrated sulfuric acid to the ethanol, and distill the ethanol.
The H, SO1 acts as an oxidizing agent for aldehydes, and this step also reduces the content
of amines.
Step 2. Redistill the ethanol from solid sodium hydroxide, to remove entrained sulfuric acid
and acidic impurities.
Step 3. Fractionally distill the ethanol with a good rectification column.
This combined treatment is said to reduce the content of aldehydes and ketones to <1 ppm, and
make the ethanol a solvent suitable for spectroscopic studies of solutes in the ultraviolet
region.
REFERENCE: B. Glabik and H. Sobczyk, Chem. Stosow, 18, 187 (1974); C.A., 81, 145492 m.
--------
This purification process is applicable to lab reagent ethanol, where typical impurities are other alcohols (methanol,
propanol) , acetone, and water.
---
I've not seen mention of activated carbon in any publications, so I am definitely curious to see where this stems from so I can do some more reading.
[Edited on 5-2-2014 by ZIGZIGLAR] copy/paste errors.
[Edited on 5-2-2014 by ZIGZIGLAR]
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DJF90
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First off, whether you rectify your own mash or commercial denatured alcohol, you'll be breaking the law (as you're rendering the spirit drinkable and
thus excise duty is due).
That being said, its useful to have pure ethanol in the lab where other lower alcohols and ketones are troublesome contaminants. The use of activated
carbon is to remove the methyl violet dye they put in "methylated spirits" to provide a purple colouration.
The means of purification will depend upon the contaminants present. In the UK the main contaminants are pyridine and methanol, so a preliminary
distillation from c. sulfuric acid is required to remove the former (and the purple dye). This distillate still has a funny smell (not sweet like lab
grade ethanol), which I suspect is some form of hydrocarbon or something. When trying to fractionate is material, using a 40cm vigreux, the boiling
point raises quite quickly to 75*C ish, and as the slow distillation proceeds, raises to 78*C. After collecting several fractions and analysing that
passing over at 78 *C for methanol (1H-NMR) it was found to be present at 6%w/w (down from 12%w/w in the commercial material). No other organic
material is found to be present but the smell is still there.
Despite the relatively large difference in bp between ethanol and methanol, you need a very efficient column in order to separate the two, as there is
little difference in composition between the vapor and liquid equilibrium curves. A more efficient column is required and a variable take-off
stillhead would be really helpful in order to acheive a decent reflux ratio.
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vmelkon
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| Quote: Originally posted by ZIGZIGLAR | Step 1. Add carefully concentrated sulfuric acid to the ethanol, and distill the ethanol.
[Edited on 5-2-2014 by ZIGZIGLAR] |
That's the recipe for making diethyl ether.
And when someone says concentrated H2SO4, I imagine they mean 90 to 98% H2SO4.
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