Sciencemadness Discussion Board - anhydrous ethanol, etoh, anhydrous alchohol, calcium oxide, quicklime, methanol?

anhydrous ethanol, etoh, anhydrous alchohol, calcium oxide, quicklime, methanol?

Hermes_Trismegistus - 11-1-2004 at 16:50

It may not be possible for me to obtain anhydrous alchohol/s OTC.

I have read that they can be prepared quite easily by running a stream of alchohol over thin slices of sodium metal, seems like a wonderful process.....except I may not be able to purchase Na metal. I have read of another simple process, distilling EtOH (ethanol) over Calcium Oxide(quicklime). I don't know of anyone who carries this substance OTC, it is very caustic and produces large amounts of heat on slaking with water.

I do however, feel that the production of Calcium Oxide from Calcium Carbonate is well within the abilities of Joe Everyman. It might present some difficulty in the Lab setting because of the high temperatures involved, but off of the benchtop, the required heat is well within the means of anyone with a backyard.

To produce quicklime from chalk (CaCO2---> CaO + CO2) you must bake the chalk at above 825 degrees Celcius. Not a temperature to be easily reached and sustained by the burning of propane or natural gas. However, this is a comparatively low temperature for one commonly overlooked and underespected fuel. Charcoal. With charcoal and a blower, you can easily and quickly reach a couple thousand degrees.

Making the "kiln" would be easy to any backyard barbeque'er but I'll elaborate for the uninitiated. You'd want to place a cast iron pipe in the flue of a charcoal furnace, because placing the "retort", directly in the coals would create hot spots that could easily melt the pipe.

To make the furnace, I will place an incomplete circle of cinder blocks on a flat dry surface (not dirt, the evaporated water cools the inside of the kiln) lay a piece of pig wire (very thick wire mesh) over the first layer of blocks so that you have a grate to hold the charcoals. Leave a space in the bottom row to receive the blower nozzle, and then continue the next circle of cinder blocks one on top of the other in a stack until you have a tower of cinder blocks at least four tiers high, place a layer of coarse granite gravel on the pig wire mesh (to protect the mesh from the intense heat of the burning charcoal) However the pores between the gravel must be large enough to allow a great deal of air to flow between the stones, it would also be wise to leave the largest concentration of stones on the outer rim. That will allow the flow of air to direct itself most intensely to the center of the burn (but let's not split hairs).

Then "charge" the furnace with a hell of a lot more charcoal than you think you need. Place another layer of pigwire mesh just above the coals (because you, as an amateur will blow way too much air into the furnace before the fire can handle it and you don't want flaming peices of charcoal all over the neighborhood)

Layer as many more layers of cinder blocks onto the stack as you can without making it too tall to handle, suspend your chalk charged vessel in the flue and wait until the obvious evolution of Carbon Dioxide gas ..........I'll finish this later.......gotta go right now.

Polverone - 11-1-2004 at 18:37

I've done this before, using a charcoal (wood) fire and chunks of marble. The process takes a while, and the evolution of CO2 is not obvious. The chemical transformation is profound, though.

Simpler would be a preliminary distillation from anhydrous MgSO4 or another similar drying agent, then addition of magnesium metal, reflux, and a second distillation for very dry alcohol (magnesium alkoxide forms and reacts with remaining water). Amalgamated aluminum might substitute for the magnesium.

On the other hand, calcium oxide has multiple uses and large-scale, high-temperature chemistry is fun.

ech310n - 11-1-2004 at 18:43

Darn it, as I was posting this I realised Polverone just did

MgSO4 can be made anhydrous by heating it in a suitable oven at temperatures over 200*C for 30 minutes or more.

Mumbles - 11-1-2004 at 19:32

http://chemdat.merck.de/cdrl/services/labtools/en/table_orgs...

This page may help in the drying of ethanol, in addition to many other compounds.

ech310n - 11-1-2004 at 20:22

I just remembered the tables at Rhodium:

Drying Agent Selection Guide
Drying Agent Data

Them two tables have been invaluable to me and strangely enough haven't been mentioned in this topic yet.

to honour my title:

Organikum - 12-1-2004 at 10:25

drying EtOH not making CaO is called for?

- industrial ways.
azeotropic destillation using benzene which forms an ternary azeotrope with the water and the EtOH.
Buhuuuu .... I have no benzene? Toluene works also - not so time effective but works.

Salting out. With or without distillation. Often adding salt makes the alcohol and water separate by themselfes - IPA for example with NaCl. Try different salts and add distillation - works nearly always. The changing of the properties of azeotropes by salts is the common industrial method of choice - fast, easy, cheap and endless scaleable in continous processes.

But for the utmost overdry alcohol you MUST use an (explosionproof) hairdryer. Bonedry. Promised.

addon

Organikum - 12-1-2004 at 10:37

CuSO4 is very usable for EtOH. Just change the CuSO4 several times and shake shake shake in between. Or stirr. The process of uptake of water by drying agents takes it time. Most ppl are just not patient enough.

You may also look for somebody with incontinenzia. Give this person the bottle with solvent to dry and wait. As such a person cannot hold the water for a long time he will loose it and the alcohol will be left waterless. (thats a new concept I admit, but a interesting approach I want to say...)

vulture - 12-1-2004 at 12:24

Drying ethanol with Na will not work as it reacts with Na to form sodiumethoxide.

This is actually a safe way to destroy sodium waste in the lab.

Mumbles - 12-1-2004 at 17:09

Would not the Sodium Ethoxide then react with the water? The reaction would then form more ethanol and Sodium Hydroxide. I suppose the Ethanol, and sodium Ethoxide would exist at equilibrium though as the reaction of NaOH and Ethanol also forms the ethoxide, but water too.

vulture - 13-1-2004 at 10:58

IIRC,

NaOH + C2H5OH <---> C2H5ONa + H2O

is situated to the left. It certainly is for sodium methoxide.

mattman1978 - 8-8-2005 at 06:58

Obtaining Dry IPA

I saw a post similar to this and I thought I would respond. Partly to help others, partly to get some advice. In industry, we avoid the use of Benzene when doing ANYTHING. Health effects are BAD. Instead, we use heptane as an azetroping agent in the azetropic distillation of IPA and water. Is a Very simple distillation. Simply distill to a splitter, remove the bottom layer (heavy phase) and reflux the top layer to a packed column.
You WILL eventually get a dry mixture of IPA and heptane in the bottom. And it will go to 0.01 % moisture or better! Problem is, in the plant, this is EXTREMELY wasteful with respect to the afor mentioned bottom layer. The stinking layer has a LOT of IPA and some Heptane. (IPA actually works pretty well to dissolve heptane into water). Oh and we are useing the cheap heptane, mixture of isomers. Cyclohexane also works well. Anyhow, does anyone else have any good ideas for azetroping agents? They must be generally non reactive and must boil up with the IPA/water mixture.

Oh and once you are done getting it dry, you can SLOWLY take off the heptane or cyclohexane off the top of the column. You should still try to send about 90% of what is boiled up back down the column while slowly removing the heptane in order to provide purer heptane and avoid wasting a lot of IPA.

This does work for IPA, NPA, and Butanol. May work for Ethanol, but I've never tried it. I believe hexane is used for ethanol.

I have used the sodium method in lab to dry non acohols, but it can be a little dangerous. Also, I know alcohols will react with the sodium metal, we used those to slowly "kill" the sodium. Maybe it was the moisture in the alcohols, not sure. I just know we used IPA to knock out the worst of the sodium and then we used ethanol to finish it off.

Anyhow, any suggestions or any questions, just drop me a line.
Matt

Your answer can be found in ...

The WiZard is In - 1-7-2011 at 12:14

Braurer. Le book is in the forums library.

Db33 - 8-12-2016 at 17:38

i saw a video on youtube and the guy made anhydrous ethanol from 95% by using 3A molecular sieves. Why is that not an option? or is it?

Dr.Bob - 9-12-2016 at 07:30

3A mole sieves work fine, but it takes a lot of sieves, and you lose some ethanol to the sieves as well. For small amounts, they work great, or if you have a huge column and can regenerate the sieves, it is great also. That is how industrial ethanol is dried, they have several multistory sieve columns, they dry ethanol in a few in series, then switch to another set of columns and then steam heat the first ones to regenerate them, likely having to trap the ethanol and water they release in a cold trap to recycle back into the system, to prevent too much ethanol from going into the air, as it can contribute to smog in large amounts via acetaldehyde formation.

Db33 - 9-12-2016 at 07:54

for regeneration i always thought sieves could just be baked like epsom salts, but you mean they need a column?

Tsjerk - 9-12-2016 at 08:11

Baking is fine, Dr. Bob is talking about industrial setups (where they in principal are also baking).

zed - 12-12-2016 at 19:48

Ummm. I always imagined that CaO was an easy get. The older literature relies upon it's drying properties often. Apparently, it is not as commonplace as it once was.

Other than chemical suppliers, I have been coming up empty.

Not cheap on ebay. And, such a material, kinda need to be cheap!

http://www.ebay.com/sch/i.html?_from=R40&_trksid=p205060...

[Edited on 13-12-2016 by zed]

[Edited on 13-12-2016 by zed]

PirateDocBrown - 13-12-2016 at 09:11

I was astonished about the low availability of tech grade CaO, as well.

In both academic and corporate labs, in my experience, it's seen as a dirt cheap and common chemical.

I even remember a bottle of it in my childhood chemistry sets!

I would be thinking that any brickmason ought to have access to it, in 50 pound bags. But checking places like Home Depot has come up dry.

[Edited on 12/13/16 by PirateDocBrown]

PeterC - 14-12-2016 at 09:29

CaO is one of those enigmatic reagents that somehow ends up being very expensive even when looking at cheap suppliers. Acros sells 1kg for 19 euro (actually decent compared to other prices I found in the EU)

beerwiz - 14-12-2016 at 16:14

The best OTC way to dry ethanol or methanol is using tapioca pearls. They look like molecular sieves and will absorb all of the water in less than 6 hours; 100g of tapioca pearls will adsorb 25ml+ of water, and you've got nearly 100% pure alcohol after filtering. You can buy them from most Asian or Chinese supermarkets. Corn grits are also effectve but will adsorb 19ml water for every 100g of corn grits. Equally effective are corn starch and tapioca flour, they are more common and can be found in almost any health food store and most supermarkets.

CaO is next to impossible to find OTC other than doing a special order and it's not cheap, if you are lucky you may find it at a building materials supply place but there's a slim chance.

[Edited on 15-12-2016 by beerwiz]

tapiocapearls.jpg - 10kB

[Edited on 15-12-2016 by beerwiz]

[Edited on 15-12-2016 by beerwiz]

[Edited on 15-12-2016 by beerwiz]

wg48 - 14-12-2016 at 18:52

Quote: Originally posted by beerwiz

The best OTC way to dry ethanol or methanol is using tapioca pearls. They look like molecular sieves and will absorb all of the water in less than 6 hours; 100g of tapioca pearls will adsorb 25ml+ of water, and you've got nearly 100% pure alcohol after filtering.

[Edited on 15-12-2016 by beerwiz]

Wow +25ml per 100g would be good almost as good as CaO but it does depend on what nearly 100% alcohol means.

The only reference I could find for its effeciency was 11% w/w with hot wet alcohol vapor (80/20% alcohol/water). That would be a lot less with 99% alcohol, probably less than 1%.

https://www.researchgate.net/publication/271970826_Desiccant...