Sciencemadness Discussion Board

Recycling solvents in acetic acid extraction of vinegar?

Mesa - 2-7-2013 at 21:01

Unfortunately, GAA is near impossible to get here, ditto to H2SO4 and HNO3. I'm attempting to extract acetic acid from storebought vinegar by saturating in NaCl, and adding Isopropyl alcohol.
Obviously evaporating the IPA would be a colossal waste of resources, and distillation is not possible due to cracked leibig condenser, however given the freezing point of IPA is -87*c, would there be any issues with throwing the IPA layer in the freezer, then filtering once acetic acid has formed a solid mass?

What contaminants(other than water) could I expect if I were to try to reuse the solvent later on?

The container I'm using is glass, however if Isopropyl acetate is a bi-product here, could I simply move it to a steel container?

I've read every thread on these forums that googling "acetic acid site:www.sciencemadness.org" gives me, most of which are focussed on sodium acetate/H2SO4 method.

EDIT:
When mentioned in a previous thread, it was assumed that the conc. of acetic acid in the IPA was around 16%. I havn't been able to find anything on miscibility of acetic acid in IPA, but given that the solution didn't become bi-phasic untill addition of IPA, I'm assuming that the acetic acid doesn't share the same properties as IPA in this respect.

Also, this thread may be more suited to the beginners section. I have no formal education in chem whatsoever(I took physics:() but I assumed given previous threads related to this had been posted in O-chem, it would be fine for this as well.


[Edited on 3-7-2013 by Mesa]

Nicodem - 3-7-2013 at 00:31

Quote: Originally posted by Mesa  
Obviously evaporating the IPA would be a colossal waste of resources, and distillation is not possible due to cracked leibig condenser, however given the freezing point of IPA is -87*c, would there be any issues with throwing the IPA layer in the freezer, then filtering once acetic acid has formed a solid mass?

First of all, acetic acid is also volatile, so you can't obtain acetic acid by evaporation. The separation would require a good distillation column (assuming there are no azeotropes between acetic acid, 2-propanol, water and isopropyl acetate).

Next, didn't you mention of taking physics? Then how come you seem to believe something as counterintuitive like that solutes just freeze out of solutions as if they were pure substances? There is no acetic acid as such in its solutions. There is only solvated acetic acid present there. So the melting point of pure acetic acid does not apply anymore (the melting point is a material specific physical property). Please see the theory of phase transitions.
Just to demonstrate how counterintuitive your belief is: If the laws of physics would suddenly change in such a way that the phase transition points of the sulutes become identical to those of pure substances, then the sodium chloride would just drop to the bottom of the oceans. Meanwhile, you would not be able to have a cup of sweet tea anymore, not just because sugar would not be soluble anymore, but also because we would all just die immediately - most of the solutes in our body would solidify or crystallize out of the cytosol and bodily liquids.

PS: Please open threads without references only in the Beginnings section. Read the forum guidelines for more information and welcome to the forum.

testimento - 3-7-2013 at 05:50

Could you oxidize ethanol with oxygen and copper oxide catalyst to acetaldehyde and over to ethanoic acid? This kind if copper tube distillation setup isn't hard to make and should in theory be capable of manufacturing several liters of acetic(ethanoic) acid within one process.

I did a test where I put 2 liters of vinegar and 500ml of chloroform and salted the water with NaCl to get chloroform saved and separated and distilled chloroform off and I got very strongly acetic smelling liquid, but it had impurities in it and even some salt crystallized out of the solution when I left it in partially closed container for months. One could have distilled over the acetic-containing fraction too, but I didn't bother since the amount was so small.

The otc vinegar contains all kinds of impurities, you can put 20ml on a ceramic plate and put it on heating plate and distill the vinegar off and you will be left with small amount of charred residues, so in all methods, the more concentrated acetic fraction should be distilled over.

bfesser - 3-7-2013 at 06:16

<strong>Mesa</strong>, I recommend preparing acetic acid by distillation of a mixture of sodium acetate and sodium hydrogen sulfate, as has been <a href="viewthread.php?tid=16725">discussed previously</a>. Extraction and purification of ethanoic acid from vinegar is too time consuming and difficult. Welcome to ScienceMadness.org, by the way! Nice to see a detailed and thoughtful first post.

[edit]
Ethanoic acid is the systematic name for acetic acid. Sorry, I don't know why I typed that.

[Edited on 7/3/13 by bfesser]

Mesa - 3-7-2013 at 14:49

@Nicodem: Yeah, I realised the obvious logic errors shortly after editing.
Also, no azeotrope is formed with Acetic acid and Isopropanol:
http://www.ddbst.com/en/EED/AZD/AZD%20Acetic%20acid%3B2-Prop...

@testimento & bfesser: Thanks for the replies, they were quite interesting to me, however the idea behind this project was the production of acetic acid in high concentration without the use of distillation apparatus.

As I said in the OP, I'm quite(read: Extremely) inexperienced with chemistry in general, and labwork in particular. I managed to crack my leibig condenser a few days ago and wanted to see if I could produce AcOH without one.


Edit: Although this method is unavailable to me at the moment(as it involves distillation) supposedly adding ethyl acetate will somewhat solve the issue of acetic acid/water azeotrope.(German Patent 28064 Dec. 18, 1883)
I wish I could be more specific however my lack of knowledge in the area means at best, I would be typing out, word for word, the mechanism as I learned it.
http://archive.stevens.edu/ses/cems/UG/sdp/project/LiquidToL...

[Edited on 3-7-2013 by Mesa]

testimento - 3-7-2013 at 22:05

There we see the distilling apparatus is a mandatory for even amateur chemist, even so precious, I'd say to make one by bending stainless steel or buying 316 nominal pipe joints and assembling it that way if the oppressive state prohibits sales of such devices.

I can point out few synthesis where distillation is not needed or at least handy for solvent recycling. One could just boil the solvent off, but for me solvents like chloroform are not something to be wasted like that, producing one liter of chloroform requires at least 5kg of anhydrous hypochlorite and 2 liters of acetone.

ElizabethGreene - 8-7-2013 at 10:54

Can you repair (epoxy?) your condenser? If you've got that then it a lot of options open up for you. Failing that, can you fabricate one out of hardware store materials?

My route from store bought vinegar to glacial acetic acid would be:

White distilled vinegar titrated to neutral pH with Sodium Hydroxide (drain cleaner) or Sodium Bicarbonate (Baking Soda) to yield Sodium Acetate (aq).

Sodium Acetate(aq) evaporated ... or gently boiled, not exceeding 115c and recrystallized to Sodium Acetate Trihydrate (s).


(This Recrystallization is _cool_, search youtube for "Hot Ice".)

Optionally, Sodium Acetate Trihydrate (s) to Sodium Acetate Anhydrous (s) by hot dessication above 58c (where the trihydrate loses its water of hydration) and less than 115c. It decomposes at 122c.
Ref: http://en.wikipedia.org/wiki/Sodium_acetate

Sodium Acetate Anhydrous (s) (limiting reagent) and Sodium Bisulfate (s) (Pool pH reducer) (in excess) dry distilled, yielding Glacial Acetic Acid.
Source (http://www.youtube.com/watch?v=QQWvgLxtldc)

I've not seen 15% vinegar. My generic store brand distilled vinegar is marked as 5%.

HTH

ElectroWin - 8-7-2013 at 11:59

Quote: Originally posted by Mesa  
Unfortunately, GAA is near impossible to get here, ditto to H2SO4 and HNO3. I'm attempting to extract acetic acid from storebought vinegar by saturating in NaCl, and adding Isopropyl alcohol.


to concentrate acetic acid without a good fractionating column, it has been recommended to me, to distill with large amounts of CaCl2 (up to 50%) which will retain the water until the acetic acid comes over

Mesa - 13-7-2013 at 13:12

Figured I'd update this thread with some(as far as I can see from previous SM threads) new findings. New condenser has arrived, however as I mentioned previously, H2SO4(in any concentration) is next to impossible to source here, and the sodium acetate/sodium bisulfate method is meant to be notoriously difficult. Also, given that I really don't know what to do with the GAA once I get it, this is basically an exercise in academia for me. Anyways...

To start, I found a pretty old patent for concentration of Acetic acid and subsequent production of GAA(the latter part requiring distillation, therefore I'll only be using the former.)
http://worldwide.espacenet.com/publicationDetails/originalDo...

Previously, some of the members here have attempted to concentrate vinegar by freezing, then melting a fraction of the solid, with varying results. In this patent, they claim to achieve 60% purity by a relatively similar method, except to pressurize/stir the mixture as ice starts to form, thus minimizing the amount of AcOH that may be trapped in the ice crystals. It goes on to say that addition of urea, sodium acetate, or potassium acetate in stoichiometric ratios can precipitate(in the case of urea) CO(NH2)2.2CH3COOH crystals of uniform structure at 0*C(eutectic point is -17*C, which is 9*C more than that of 60% acetic acid)

I believe standard paper filters should be able to replace centrifuging the mixture in order to obtain solid CO(NH2)2.2CH3COOH. Thawing will result in urea dissolved in GAA.

At this point I could just distill and get my GAA and have only used urea to do so, but given that I havn't theoretically had to use any lab equipment so far, I want to see if its possible to purify without distillation.

This paper describes a method of obtaining GAA by sweating out with a seed crystal:
http://www.aidic.it/isic18/webpapers/85Choi.pdf

Obviously this requires GAA as a precursor, and as such is a catch 22 for this scenario.

My question(and therefore, vindication for having bumped an oldish thread;)) is if it would be possible to use the urea.acetic acid double compound crystal as a seed? I've found little literature on this, but I assume it probably wouldn't work.

Mesa - 13-7-2013 at 13:24

For some reason I can't figure out how to edit my posts with this forum software, sorry for the double post.

Another possibility that occurred to me while reading into this was the idea of using a chemical which has the ability to co-crystallize with acetic acid. One of the studies I read spoke of a major impurity found in illicit methamphetamine samples being methylsulfonylmethane, it mentioned that the two substances could form a co-crystal(can't find the ref in my history unfortunately). Many wikipedia pages later I started to vaguely understand the concept of co-crystallization, thus, the idea of using this, in addition to the sweating out method in the above post, could possibly yield GAA without the need for any lab equipment whatsoever.

Hence, the search begins for a substance that can form a co-crystal with acetic acid.