Sciencemadness Discussion Board

Alternate route to dry ethanol

evildrome - 11-8-2014 at 03:15

I recently bought some gallium to muck about with gallium/aluminium amalgam.

Having reacted it with TSDA (ethanol) to make aluminium triethoxide it occurred to me that adding excess TSDA would destroy any water in the ethanol (by consuming the aluminium triethoxide)

You'd need to do the math to work out ideal proportions but its a route to dry ethanol that doesn't involve metallic sodium.


[Edited on 11-8-2014 by evildrome]

hyfalcon - 11-8-2014 at 03:50

Ethyl acetate/Sodium hydroxide still seems easier to deal with to me anyway.

DJF90 - 11-8-2014 at 04:00

Anhydrous ethanol is best made by distillation from magnesium

evildrome - 11-8-2014 at 07:04

Horses for courses. If you've got gallium but don't have either ethyl acetate or magnesium its a way forward.

I agree though that magnesium sounds like an easier route.

I've never tried 3A sieves but would like to. The price on Ebay UK appears to be GBP 20 per kilo plus £8 post.

That sounds quite pricey.

gdflp - 11-8-2014 at 07:08

Couldn't you just reheat them to reactivate them? If that was the case, then it's fairly cheap compared to buying anhydrous ethanol.

evildrome - 11-8-2014 at 07:29

Yes, they're recoverable which is very attractive.

I might just bite the bullet & get some.

papaya - 11-8-2014 at 14:31

Always wanted to try CaC2 as a drying agent, will it work?

Pyro - 11-8-2014 at 15:42

sounds like a bad ides, liberationg relatively large amounts of highly flammable gas from a flammable liquid...

Burner - 11-8-2014 at 15:54

Quote: Originally posted by gdflp  
Couldn't you just reheat them to reactivate them? If that was the case, then it's fairly cheap compared to buying anhydrous ethanol.

Regeneratong the molecular sieve beads or pellets is easy, especially if you have access to a vacuum oven and a good mechanical pump. The powder is much more difficult to regenerate.

TheChemiKid - 11-8-2014 at 18:05

I would use everclear as my alcohol source (if it is legal where you live), and distill over molecular sieves (not the powder).
That method is relatively cheap, and the sieves are regenerable.

arkoma - 11-8-2014 at 19:13

short question----stoichometric amounts of NaOH and EtAcetate=Sodium acetate and 200 proof booze?

Because I have both, mua-ha-ha

Magpie - 11-8-2014 at 19:35

Working definitions (mine):

1. Everclear = distilled spirits = 95% ethanol
2. Commercial absolute ethanol = 99% ethanol
3. "Super dry" ethanol = 99.9% ethanol

Without a Karl Fischer apparatus or other instrumentation it is hard to determine when your ethanol is "super dry." But if you have had good success with it in those reactions that require it, then it is likely "super dry," I would think.

There is a paper* that provides the results of several methods for making "super dry" ethanol. The method par excellence was 3A mole sieves. But the starting point for all these tests was 1500ppm (0.15%) ethanol. My concern is that I don't know if you can go right from Everclear to "super dry" with just the 3A sieves. I think some on this forum have recommended against trying this. Taking their advice I went from Everclear to "absolute" by distilling over burnt lime (CaO). I caught the distillate in a receiver loaded with the 3A sieves. The "super dryness" of my product was verified by a successful reaction which required it.

I put this information out FYI, not as anything dogmatic. I'm simply relaying my experience for your consideration. In theory I don't know why one couldn't go directly from Everclear to "super dry" using the proper amount of 3A mole sieves.

*"Desiccant Efficiency in Solvent and Reagent Drying. 7. Alcohols," by Burfield and Smithers, J. Org. Chem., 1983, 48, 2420-2422

[Edited on 12-8-2014 by Magpie]