Sciencemadness Discussion Board

Using calcium chloride to remove MeOH from EtOH - Is it possible?

SuperOxide - 3-9-2021 at 08:14

I've used anhydrous calcium chloride as a desiccating agent for a while since it not only complexes with water, but also alcohols. But I just found this quora answer that suggests anhydrous calcium chloride can be used to purify EtOH by removing only the MeOH.
Quote:
Ethyl alcohol can be separated from methyl alcohol chemically by adding anhydrous calcium chloride which forms complex with methanol but not with ethanol. Then the crystalline complex may be filtered and heated to get back methanol while the residue of the filtration remains as ethanol

I thought both EtOH and MeOH form complexes with CaCl2... Has anyone tried this before?

Fyndium - 3-9-2021 at 09:31

To be honest, Quora would be one of the less credible source in my opinion. I've seen multitude of suggestions, speculation and second guessing with things that are far away from facts that I knew of.

But, for the matter, separating IPA and ethanol would be a more interesting venture.

clearly_not_atara - 3-9-2021 at 11:43

I doubt that separating MeOH from EtOH is easier than decarboxylating lactic acid. Apparently this can be achieved by photolysis:

https://pubs.rsc.org/en/content/articlelanding/2021/CP/D0CP0...

SuperOxide - 3-9-2021 at 19:43

Quote: Originally posted by Fyndium  
To be honest, Quora would be one of the less credible source in my opinion. I've seen multitude of suggestions, speculation and second guessing with things that are far away from facts that I knew of.
Yeah... I agree. I guess it was just hopeful thinking, lol.
Quote: Originally posted by Fyndium  
But, for the matter, separating IPA and ethanol would be a more interesting venture.
Right, but I can easily get/purify IPA, so thats not an issue. The ethanol I have and can easily get is usually denatured with MeOH (and a few other things that are easier to remove).

Fyndium - 3-9-2021 at 22:01

Would it be enough to fractional distill the methanol off from ethanol? They generally have similar properties as a solvent, so traces of neither would not be too critical.

Tsjerk - 4-9-2021 at 02:25

Methanol is more acidic than ethanol, therefore magnesium reacts faster with methanol than with ethanol. You could stir magnesium shavings with dilute HCl to clean it, rinse with water, and stir it with dryish alcohol. Then you distill and you will have anhydrous alcohol with less methanol.

You will get an equilibrium between methoxide and ethoxide, but with e.g. 1% methanol and 99% ethanol and with let's say ten times the magnesium to react with the methanol you will take out 99%+ of the methanol.

You could use the (m)ethoxide to dry ethanol where a bit of methanol doesn't matter.

SuperOxide - 4-9-2021 at 09:34

Quote: Originally posted by Fyndium  
Would it be enough to fractional distill the methanol off from ethanol? They generally have similar properties as a solvent, so traces of neither would not be too critical.

If it was for a solvent then just getting rid of the water would be sufficient, but I actually have a few experiments that I would like to try with pure ethanol. diethyl oxalate, sodium ethoxide, etc.

Quote: Originally posted by Tsjerk  
Methanol is more acidic than ethanol, therefore magnesium reacts faster with methanol than with ethanol. You could stir magnesium shavings with dilute HCl to clean it, rinse with water, and stir it with dryish alcohol. Then you distill and you will have anhydrous alcohol with less methanol.

You will get an equilibrium between methoxide and ethoxide, but with e.g. 1% methanol and 99% ethanol and with let's say ten times the magnesium to react with the methanol you will take out 99%+ of the methanol.

You could use the (m)ethoxide to dry ethanol where a bit of methanol doesn't matter.

Hmm... That's an interesting idea. I have like 30g of magnesium ribbon. I have more magnesium powder than I do ribbon though. But I know the magnesium + alcohol is exothermic, so adding powder might not be the best idea.

Tsjerk - 4-9-2021 at 10:37

If you have a reflux apparatus you could use that to do the alcohol/magnesium reaction in. I don't think the reaction with magnesium powder would be so vigorous you can't handle the possible boiling with some cooling water. But of course don't start with all powder at once to be sure.

SuperOxide - 4-9-2021 at 19:12

Quote: Originally posted by Tsjerk  
If you have a reflux apparatus you could use that to do the alcohol/magnesium reaction in. I don't think the reaction with magnesium powder would be so vigorous you can't handle the possible boiling with some cooling water. But of course don't start with all powder at once to be sure.



Right. I only have 1 liebig condenser, which isn't super efficient. I have a friedrich condenser on my to-buy list. I may buy that first, just to be safe, lol.