Fractional Freezing - 100 % Alcohol ??

buy a good bottel of Vodka

Amen brutha!

Fractional freezing wouldn't freeze pure water from the solution, but rather a dilute solution of alcohol in water, which can then be removed. As the temperature of the solution drops, the concentration of alcohol in the portion that freezes would increase. At low enough temperatures, the entire remaining solution would freeze. Don't know what the minimum water concentration that you could obtain this way would be, but would probably be distinctly non-zero.

Why not re-still it has to be cheaper and faster than freezing

but I'm not an engineer

It's aphysical chemistry problem

4% water is what you are left with no matter what way you distill it. It's akin to a eutectic alloy.

I believe that you can remove the water with CaO, but check first that this is not explosive before trying it. I dont think it is potable after such treatment

re distillation always brings water across - it gives an azeotrope. Industrially I believe this is removed by the use of a light aliphatic solvent which messes up the azeotrope.

Calcium Oxide or plaster of paris should work and should leave no toxicity - neither slaked lime nor plaster is soluble in alcohol.

Industrial alcohol contain goodies which are difficult to remove - you would need to start with vodka or a reagent quality ethyl alcohol.

You may use a desicant heat transfer roll that would remove the water. However you would have some Alcohol evaporation as well, 1-3%.

Not possible.

Better to heat the solution above the boiling point of alcohol and less than the boiling point of water. Let the alcohol condense.

Hi,

this is done conveniently with Calcium-Chloride (CaCl2) that absorbs the water, the solution that forms from the liquefied CaCl2+water is not miscible with the alcohol so can be separated easily.

The solution of CaCl2+water can be regenerated by heating.

The same principle is used in air dryers: simple for household and high performance for airbearing supply.

RHABE

I believe that 96% Ethanol exists as an azeotrope and cannot be seperated using a freezing technique. The only way to remove the water is to add a third component such as benzene and then distill off the products. The benzene is recoverable for reuse in the process after the distillation. I'm sure the net will have further information to allow the columns are to be designed. Good luck.

Even If you can get rid of the last 4% water, any exposure to air and the alcohol will start adsorbing the moisture from the air. So if you are able to achieve the 100% alcohol you will have to keep it in an completely closed system.

If I remember correctly from a biologist friend who worked with absolute ethanol in the lab, if you were to obtain 100% ethanol, then it very quickly reverts back to a little bit of water and some other compounds in equilibrium. They could not obtain pure alcohol as such.

the far simplest method is to use a molecular sieve. Zeolite

Zeolite is a synthetic aluminum-silica material. The surface of which is covered by pores of a certain size. Three angstrom and four angstrom zeolite are suitable for the dehydration of ethanol. The "pore size" of the zeolite gives the critical diameter of the molecules it can adsorb. Three and four angstrom zeolite are usually used as dessicants to remove carbon dioxide and water. The critical diameter of ethanol is 4.4 angstroms. Because of this, its molecules will not fit in the pigeon-holed surface of the zeolite. Water has a critical diameter of around 2.4 and is readily adsorbed. Zeolite is not consumed in the process. It can be regenerated by heating to boiling point of the substance it has adsorbed.

From: http://theethanolsource.com/library/index.php/Ethanol_process

The suggestions of using CaO or Zeolite look good to me. In the past, when I needed 100 % alcohol, we added metallic sodium (Yes, avoid a violent reaction) and then distilled it again. The NaOH did not come over with the distillate. Yes, you must keep pure alcohol away from air.

Just as an aside, the object of the exercise was to make pure Ca-Ba-Al oxides (to use in cathodes for high-power vacuum tubes). We reacted the metals with the water-free ethanol, then added water. The metal oxides precipitated out in the correct proportions and intimately mixed. Unfortunately, someone else patented the process, and we gave up on it. (We also had a problem in that our purchasing deptartment didn't believe we needed <<really pure>> water, and they substituted "pure distilled water" which had traces of Cl, which poisons cathodes. It's easy to waste money that way)

Mole sieve A3 -- (not 4A or it will absorb the alcohol too) -- the absorbtion is exothermic - go slow

google UOP chemical for the sieve -- we use them in Polyurethane elastomers to removel "all" water

i am curious:

Why would you want to do that?

We are familiar with 3A zeolites and the process. However, in order to "regenerate" the zeolite bed, you must use a large amount of heated nitrogen for a large period of time. The N2 is expensive were I live and the volume of N2 is also large except if you apply another circulation loop, adding more expenses for a very small volume. I have heard that the perfume industry uses liquid nitrogen which is less expensive to remove the 4% of water to convert the alcohol to 99.5 % We realize that alcohol is azotropic @ 96% and also that it absorbs humidity. We have a rectification column where we improve the alcohol and remove odors.

Thanks for your comments