How to remove amines from wood tar

[reagent31]

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

[ChenBeier]

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

[reagent31]

Thanks so much. What kind of dilution would be recommended for the hydrochloric acid prior to mixing with the tar?

[ChenBeier]

Theoretically you can use conc. HCl 37. % w.w. But 25 % w.w. would be fine for handling.

[reagent31]

Great, thank you. I'll likely try the 25% w.w. first. Just two more questions: 1. For a 100 mL tar volume, how much of the 25% w.w. HCI should be used? 2. Would ethanol be a suitable solvent for amine, or is the HCI superior?

[ChenBeier]

I would try first 10 ml HCl for 100 ml tar. Ethanol can be used but it will dissolve also other compounds. The acid is able to convert the Amin in water solouble compounds.
As other people mentioned how is the viscosity of the tar.

[reagent31]

The viscosity is a bit thicker than maple syrup, perhaps more like molasses. So the 10 ml of HCI would be the 25% w.w. HCI and not undiluted HCI, correct?

[ChenBeier]

Correct. Check pH then you are sure all amine will be catched.

[reagent31]

Ok, so there could be need to do more than one wash to catch all the amines? And once ph of HCI solution stays the same pre and post wash, can assume all amines have been scrubbed? Ty and cheers.

[ChenBeier]

Yep, according Nernst law, it is more efficent to do multiple washing with lower volume of washing solvent.

[bessieelliott]

Nernst law says repeated washing with less solvent is more efficient.

[ChenBeier]

That is what I am saying.

[Pocki]

The choice of solvent depends on the specific impurities you want to remove. For amines, polar solvents like water or aqueous solutions of acids or bases can be effective. However, since wood tar contains a complex mixture of compounds, a trial-and-error approach might be necessary to determine the most suitable solvent. It's recommended to start with a small-scale test before scaling up.