Sciencemadness Discussion Board

CopperIISulfide

Noflers - 2-3-2016 at 18:52

I have a few questions that have come to me, they involve alcohol fermentation, but mostly distillation of the ethanol.

Home distillers and, I would guess commercial distillers as well, us copper in their distillation apparatus due to its ability to strip ethanol vapor of its sulfur components (which come from the fermentation process in some cases).

I am wondering what is taking place here, is Cu2S being formed? I'm guessing that it is so please correct me if I'm wrong.

In order for this reaction to take place does the ethanol need to be in gas form, or could the liquid ethanol be passed over copper mesh/stored in a copper container?

Zephyr - 2-3-2016 at 19:17

These people seem to think so: https://www.homebrewersassociation.org/forum/index.php?topic...

It appears it is actually forming the sulfate, not sure how safe that is to ingest though...
FYI Copper (II) sulfide means the copper is 2+ and so the formula for it will be CuS.

Try googling this question next time, it only took me a few minutes to find.

blogfast25 - 2-3-2016 at 19:29

Quote: Originally posted by Zephyr  

Try googling this question next time, it only took me a few minutes to find.


Sure, but what have you found?:( A very low level site, with hardly any scientific content.

It's generally recognised that using all-copper apparatus for the distilling of homebrew ('moonshine') removes 'sulphurous' compounds. It seems likely that the driving force is the formation of very insoluble copper sulphides, either Cu2S or CuS.

The solubility product of CuS is about 6 x 10<sup>-37</sup>, incredibly low.

As nearly all chemical reactions are rate-promoted by temperature, the process of boiling up the wash and condensing the distillate in an all-copper still may be an effective way of removing sulphur.

[Edited on 3-3-2016 by blogfast25]

Zephyr - 2-3-2016 at 20:03

Quote: Originally posted by blogfast25  
A very low level site, with hardly any scientific content.
[Edited on 3-3-2016 by blogfast25]


Yeah, I agree. Here's a pertinent patent if you were looking to go a bit deeper Noflers: http://www.google.com/patents/EP0527000A2?cl=en

Additionally, copper sulfide is likely responsible for the black coating sometimes developed on copper stills.
I am confident that cleansing of hydrogen sulfide in solution would work well with elemental copper, although you may be onto something in regards to elevated temperatures when dealing with heterocyclic sulfur compounds.

DraconicAcid - 2-3-2016 at 20:30

I know copper(II) sulphate is used in small amounts to remove H2S from wines.

Noflers - 2-3-2016 at 20:44

Quote: Originally posted by Zephyr  
Quote: Originally posted by blogfast25  
A very low level site, with hardly any scientific content.
[Edited on 3-3-2016 by blogfast25]


Yeah, I agree. Here's a pertinent patent if you were looking to go a bit deeper Noflers: http://www.google.com/patents/EP0527000A2?cl=en

Additionally, copper sulfide is likely responsible for the black coating sometimes developed on copper stills.
I am confident that cleansing of hydrogen sulfide in solution would work well with elemental copper, although you may be onto something in regards to elevated temperatures when dealing with heterocyclic sulfur compounds.


Nice find, thanks. That patent seems to describe the gas, but "preferably liquid" forms of organic compounds passing over copper or zinc oxides.

And yes, I did see that forum thread and others from the same forum, but wanted more, ya know?

Now I'm working on figuring out which is more efficient, zinc or copper.