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Author: Subject: Could we dry ethanol with Zinc?
VeritasC&E
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[*] posted on 29-7-2022 at 09:33
Could we dry ethanol with Zinc?



There certainly something I might be missing, but, if we put a few chunks of freshly cut zinc in 98.0% Ethanol, and bring the temperature up in a pressure cooker, would that be enough to dry it to >99.9% Ethanol?

Would we need etchant vs newly formed oxide on the surface?

I'm thinking zinc is less reactive than magnesium, so it would be safer to distill after filtration if it works.
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clearly_not_atara
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[*] posted on 29-7-2022 at 09:55


I do not think that ethanol will get through that oxide layer. Zinc powder has a chance, but a small one unless it's activated just before use. Zn/Ga amalgam would work, but that's a waste of gallium.



[Edited on 04-20-1969 by clearly_not_atara]
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MadHatter
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[*] posted on 29-7-2022 at 10:52
Home Fuel Distillation


Running your EtOH through anhydrous rock salt can remove water but I'm not
sure how much. The rock salt can be left out in the sun afterward to dry out.
This is 1 of the methods that home distillers(for fuel) use. It really depends on
your intended use. And, no, I didn't distill it for my car. :D




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VeritasC&E
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[*] posted on 30-7-2022 at 01:55


Quote: Originally posted by MadHatter  
Running your EtOH through anhydrous rock salt can remove water but I'm not
sure how much. The rock salt can be left out in the sun afterward to dry out.
This is 1 of the methods that home distillers(for fuel) use. It really depends on
your intended use. And, no, I didn't distill it for my car. :D


That's interesting. I would definitely not feel safe putting in my car stuff that's been in contact with sodium OR chloride. Neither did I know it could be used as dessicant (I did however know it was hygroscopic, for having lived in humid climates).
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VeritasC&E
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[*] posted on 30-7-2022 at 01:56


Quote: Originally posted by clearly_not_atara  
I do not think that ethanol will get through that oxide layer. Zinc powder has a chance, but a small one unless it's activated just before use. Zn/Ga amalgam would work, but that's a waste of gallium.


Is there anything that would etch the oxide layer, maybe I2? (ZnI2 is soluble in both water and ethanol, and I2 is used in conjunction with Mg for the same purpose)

[Edited on 30-7-2022 by VeritasC&E]
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[*] posted on 30-7-2022 at 03:47


I use Epson salt, dried in an oven for a few hours then crushed.
It can be added directly to the ethanol and then distilled.
I try to keep a ratio of 3:1 by weight. Salt vs water. I don't think zinc would do it by itself. At least not in a reasonable amount of time.




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[*] posted on 30-7-2022 at 13:37


Your best bet is Mg powder. It works cold, but you can reflux, then distill off the alcohol.



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VeritasC&E
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[*] posted on 2-8-2022 at 02:44


Quote: Originally posted by Rainwater  
I use Epson salt, dried in an oven for a few hours then crushed.
It can be added directly to the ethanol and then distilled.
I try to keep a ratio of 3:1 by weight. Salt vs water. I don't think zinc would do it by itself. At least not in a reasonable amount of time.


That is indeed probably the best way to get rid of the bulk of the water, but to make fully anhydrous ethanol you need to use one of different techniques after that.
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VeritasC&E
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[*] posted on 2-8-2022 at 02:48


Quote: Originally posted by PirateDocBrown  
Your best bet is Mg powder. It works cold, but you can reflux, then distill off the alcohol.


Mg powder likewise produces an ethoxide, and as you say, it probably works much better/faster cold than with zinc, because magnesium is more reactive. My idea is that if it is feasible to trade magnesium for zinc, then we might trade some drying speed for safety (in distilling it afterwards), for an equal (full drying) result (precisely because zinc is less reactive).
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unionised
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[*] posted on 2-8-2022 at 05:17


Is it just me or is " bring the temperature up in a pressure cooker," a bit worrying?
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[*] posted on 2-8-2022 at 07:28


Quote: Originally posted by VeritasC&E  
Quote: Originally posted by PirateDocBrown  
Your best bet is Mg powder. It works cold, but you can reflux, then distill off the alcohol.


Mg powder likewise produces an ethoxide, and as you say, it probably works much better/faster cold than with zinc, because magnesium is more reactive. My idea is that if it is feasible to trade magnesium for zinc, then we might trade some drying speed for safety (in distilling it afterwards), for an equal (full drying) result (precisely because zinc is less reactive).


If zinc would react with the water, what would stop it from forming ethoxide afterwards?
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VeritasC&E
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[*] posted on 7-8-2022 at 13:20


Quote: Originally posted by Tsjerk  
Quote: Originally posted by VeritasC&E  
Quote: Originally posted by PirateDocBrown  
Your best bet is Mg powder. It works cold, but you can reflux, then distill off the alcohol.


Mg powder likewise produces an ethoxide, and as you say, it probably works much better/faster cold than with zinc, because magnesium is more reactive. My idea is that if it is feasible to trade magnesium for zinc, then we might trade some drying speed for safety (in distilling it afterwards), for an equal (full drying) result (precisely because zinc is less reactive).


If zinc would react with the water, what would stop it from forming ethoxide afterwards?


I don't know, which is why I'm asking. My assumption is that the solubility in ethanol would be fairly low, such that the ethoxide would react with water and then saturate the ethanol at a fairly low solubility value, which would slow down to near nothingness further reaction.
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[*] posted on 7-8-2022 at 13:23


Quote: Originally posted by unionised  
Is it just me or is " bring the temperature up in a pressure cooker," a bit worrying?


Just a little bit above the BP of water. No worries.

Only ethoxide + water + flammable liquid inside, what could go wrong? ^^
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[*] posted on 7-8-2022 at 13:25


Quote: Originally posted by Tsjerk  
Quote: Originally posted by VeritasC&E  
Quote: Originally posted by PirateDocBrown  
Your best bet is Mg powder. It works cold, but you can reflux, then distill off the alcohol.


Mg powder likewise produces an ethoxide, and as you say, it probably works much better/faster cold than with zinc, because magnesium is more reactive. My idea is that if it is feasible to trade magnesium for zinc, then we might trade some drying speed for safety (in distilling it afterwards), for an equal (full drying) result (precisely because zinc is less reactive).


If zinc would react with the water, what would stop it from forming ethoxide afterwards?


PS: Note that Zinc doesn't react with water, zinc ethoxide would.
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[*] posted on 7-8-2022 at 21:29


The whole point is to make the ethoxide, because the ethoxide will react with any water, destroying it, and regenerating the alcohol. Meanwhile the metal oxidizes.

If you want dry ethanol, Mg is the classically preferred route.




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[*] posted on 27-8-2022 at 09:54


Quote: Originally posted by PirateDocBrown  
The whole point is to make the ethoxide, because the ethoxide will react with any water, destroying it, and regenerating the alcohol. Meanwhile the metal oxidizes.

If you want dry ethanol, Mg is the classically preferred route.


Don't know why you needed to state that, as everyone should already know all these things:

https://www.youtube.com/watch?v=NMfs3e9OdZQ
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[*] posted on 27-8-2022 at 13:17


Quote: Originally posted by ErgoloidMesylate  


Don't know why you needed to state that, as everyone should already know all these things:

https://www.youtube.com/watch?v=NMfs3e9OdZQ


Maybe because he want to explain it? Not everyone know this. This is purpose of this forum - to learn something.
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[*] posted on 27-8-2022 at 13:59


Quote: Originally posted by ErgoloidMesylate  


Don't know why you needed to state that, as everyone should already know all these things:

https://www.youtube.com/watch?v=NMfs3e9OdZQ


Thank you for putting up this link, I didn't go through the trouble of finding an explanation for why the formation of the alkoxide is irrelevant here, but you did and Doug explains it perfectly.

When there is water present, no alkoxide will be formed. Sure, alkoxides will react with water, but none will form as long water is there.
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[*] posted on 27-8-2022 at 15:12


Quote: Originally posted by Tsjerk  
Quote: Originally posted by VeritasC&E  
Quote: Originally posted by PirateDocBrown  
Your best bet is Mg powder. It works cold, but you can reflux, then distill off the alcohol.


Mg powder likewise produces an ethoxide, and as you say, it probably works much better/faster cold than with zinc, because magnesium is more reactive. My idea is that if it is feasible to trade magnesium for zinc, then we might trade some drying speed for safety (in distilling it afterwards), for an equal (full drying) result (precisely because zinc is less reactive).


If zinc would react with the water, what would stop it from forming ethoxide afterwards?
The relatively high stability of ZnO versus MgO is my guess. The latter is attacked by acids much faster.



[Edited on 04-20-1969 by clearly_not_atara]
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