Hello all,

I produced about 100 mL of wood tar via dry distillation of spruce wood in a small oven.  I would like to purify the tar product by removing amines (and a few other impurities), but am unsure about the best way to proceed.  How exactly would I perform a liquid liquid extraction to do so, and what kind of solvent would you recommend?  Thanks in advance, Thomas

Use extraction with hydrochloric acid. Amines will react to ammonium compounds soluble in aqueous Phase.

Edited June 19, 20232 yr by chenbeier

How viscous is the tar?
It might be easier if you dilute it with a solvent that you can remove later.
Maybe cigarette lighter fuel.

But how a amine should be removed by dilution. Lighter  fuel  will dissolve more hydrocarbons as polar amines.

3 hours ago, chenbeier said:

But how a amine should be removed by dilution. Lighter  fuel  will dissolve more hydrocarbons as polar amines.

It wouldn't.
But if the tar is viscous then dilute acid will also fail to extract the amines from it.

You dilute the tar, extract the amines and then remove the solvent.

Ok, agree, this makes more sense.

Would an alternative solvent like ethanol or methanol perhaps work?  And then adding a co-solvent in the form of water as a way to separate the ethanol or methanol from the tar?  As far as I know, ethanol or methanol would form a homogenous mixture with the tar, and wouldn't separate, so therefore would need water added, but I could be wrong.

If petroleum distillates like lighter fluid work better, and would it partition into a separate phase by itself, without the need for a co-solvent?

Also, would it be possible to make the tar less viscous by heating it, and then add the dilute acid?   Thank you all for your feedback.

If you can avoid the use of a solvent then you avoid teh problem of having to remove it, so warming the material up is good- if it works.
If you add an alcohol it will probably act as an emulsifying agent which makes things harder.
(The ammonium salts mat do this to some degree anyway.)


What are you seeking to achieve?

I'd like to purify the product as much as possible, so that it can be tested in a diy dog shampoo and skin spray treatment.  The coal tar offerings don't work, and am not keen on the coal tar ingredient.  In addition to amines, would also like to get rid of any phenols and polycyclic hydrocarbons that are likely present too, which I think could be taken care of with a solvent like ethanol, but not sure.   I understand that the big-name manufacturers use solvent extraction followed by vacuum distillation to purify their product, but I've no idea what solvent they are using, what they are taking out, nor why they need to vacuum distill.   Am just attempting a diy home project to see if I can make something passable for my two mutts, but at the same time would like to see if I can simulate what the manufactures do in a lab in my garage.   Thank you to you and chenbeier  for your insights so far.

If you get this wrong, what happens to the dog?

Tar is a mixture of many materials. If you didn't add anything to the stuff you distilled from wood then it's pure tar.
How could you purify something that's pure to begin with?


 

Edited June 20, 20232 yr by John Cuthber

Now we should stop the discussion. We should not give receipies to make pharmaceutical products for animals and humans as well. Who will take responsibility if an animal or human gets hurt or even worse, with our suggestions to make the product.

Please do stop the discussion if topic causes any concern.  Totally understandable, and appreciate your feedback.  Although a rookie at this, will pursue thorough due diligence in ensuring what goes on my pets is as safe as possible.  And if too much of a hassle, will order a natural product online, although takes ages to get to my neck of the woods.   Would there be any worthwhile resources that you would recommend to get fully up to speed on solvent extraction best practices, etc.?   Thank you again for addressing the topic.

Apparently, tar from biomass can contain potentially harmful levels of pahs, phenols and amines, thus my interest in seeing if feasible to remove this stuff on my own.   Thanks again.