If you are starting say with vodka you can fractionate that to 95% if you have a well lagged efficient column, a reflux ratio of at least 10:1 and you
take it slow and easy. You have to let the column equilibrate before you start taking ethanol off. That means you start with a 100% reflux.
A 10:1 reflux ratio means you return 10 drops of distillate to the column for every drop that you allow to condense into the receiver.
That means the process is SLOW. You cannot speed it up. Well you can but only with a rather expensive high throughput column. If you want to spend
$1000+ on a column I will tell you what to buy.
This setup and procedure can get you at best the 95-96% binary azeotrope of ethanol/water.
To wring that last 4-5% out and get at least temporarily anhydrous ethanol, you choose between a few techniques:
1. Zeolites (Molecular sieves) selecting the particular one that is best for removing H2O (4A I think.)
This is easy, just add the zeolite (solid) to the 95% ethanol, stir, and let it sit in a tightly closed bottle.
2. Ethanol forms a tertiary azeotrope with benzene and (IIRC) acetone. Look it up in Merck Index to get the correct proportions and ingredients. Extra
benzene will remove the water. You will then have absolute alcohol which can be distilled from the acetone and benzene leaving only traces of those.
The bad news is benzene is a carcinogen so I would recommend you use procedure (1).
3. I seem to remember a procedure using dry cornmeal as the dehydrating agent. Anyone have the details?
Once you have dry ethanol you will want to keep it that way. Store it over zeolites, or over sodium metal (then distill it off when you need it) or
over calcium oxide. Tightly capped bottle is a must. Absolute ethanol badly wants to return to that 95% azeotrope and will suck water out of the air.
If you put 100 ml absolute ethanol in a volumetric flask at correct temperature to the mark and leave off the cap you will soon have an extra 5 ml or
so in the flask and the ethanol will be back to the azeotrope and happier than a hog in a manure pile.
Why not just buy 95% potable ethanol ("Diesel" or "Everclear") at a liquor store? Then you can skip the distillation which is tedious and go straight
to the zeolites.
Oh yes I know some states have banned that stuff. But not all.
If you are starting from fermented mash you will probably need to distill 3 times to get to 95% If you have never fermented alcohol from sugar and
baker's yeast I recommend you try it, it is fun but also a glorious pain in the ass. Hard to get much better than 15% alcohol in the mash, a simple
distillation of that will get you 35-50% ethanol with a lot of congeners in it (ethyl acetate, acetic acid, acetone, amyl alcohols.)
None of this is for making anything to drink. To do that you need skill and special purification techniques to remove the congeners. Then what you
will have is rather hard won and costly VODKA. Not worth the effort.
theoretical plates, and a tall column
roamingnome - 11-1-2007 at 11:42
if one where to construct a very tall column of height infinity, wouldnt there be a point at which 95% alcohol vapours are residing and collect them
in a gutter and that height.... as they condesnce to the wall?
ive scene intersting designs for quick mass produced alcohol fuel which is what im trying to get going without spending a fortune in the process....
one where steam is injected right into a cascade of falling mash...
what??? you mean ive been drinking ethylacetate back in the kentucky woods.... ye ha... im a freak....Sauron - 11-1-2007 at 13:52
Absolutely not. An azeotrope will not be broken by increasing the number of theoretical plates (which is all you are doing with your infinite column)
All you would accomplish would be an infinitely tedious distillation of 95-96% ethanol, balance water.
Ordinary denatured ethanol ("rectified spirits") is 95% ethanol with unpalatable substances added to make it non-potable and therefore excise tax
free. This is your routine lab grade ethanol for recrystallizations etc.
Absolute (Anhudrous) ethanol is also non-potable because of traces of benzene from the tertiary azeotrope used to remove the water. But it is much
more expensive than 95%.
If you are doing reactions involving alkili ethoxides, making sodium acetoacetate, or malonic esters etc. you need very very dry ethanol and the
ordinary absolute ethanol isn't quite there. That's when it is time to distill from sodium wire (which you prepare fresh with a sodium press),
directly into a dry receiver which will be the rxn flask. The rigor of drying glassware and ethanol is similar to preparing to do a Grignard rxn, but
not as demanding as preparing to do a lithiation.
See Vogel for his instructions on super-dry ethanol.Fleaker - 11-1-2007 at 13:57
I still do not see the harm in using sieve. Some people love to use sodium wire to dry ethanol, but you lose some of your alcohol as sodium ethoxide
(in the meanwhile, producing H2 gas).
no questions asked, no invoices, just order. Shame it's not indicating, but that shouldn't be too hard for us here to achieve. Cobalt chloride anyone?Sauron - 11-1-2007 at 14:02
On subject of alcohol fuel, there's bullshit on the web about a design called "Charles 925" or something like that, skip that one because it will not
work. I bought his plans, they were goobledygook. The guy is just trying to sell special valves that are supposed to magically make the still very
efficient. I originally saw this on the Journey to Forever project website but later found they had taken it down and they had nothing good to say
about the submitter or his design, basically they said he was a con artist. Caveat emptor.
Ethanol fuel is cost effective only on a large industrial scale and by using a lot of fairly advanced process engineering well known in the alcohol
industry to maximize the efficiency of the energy expended via reboilers, heat exchangersetc etc. This is not a job for an amateur IMO.Fleaker - 11-1-2007 at 14:07
If your feedstock is free it can be made to work. I have a friend who gets free sugar beets and makes alcohol from them. It costs him $0.45/gallon to
make (materials included) the 195 proof material. He uses that with sieve and is left after a few hours with near anhydrous alcohol. Sure it's a lot
of work, but the tax rebate covers the cost.
Check out that site, there are various enzymes sold there that are useful for fermenting things that otherwise would be useless.Sauron - 11-1-2007 at 14:10
Which way to go depends on your end use.
Ethanol losses to the small amount of Na used for drying ethanol that is already absolute, are utterly trivial.
Molecular sieves are great for drying 95% ethanol but not for getting to the stage that is required for the best yields in aldol condensations, etc.
It's easily proven. Do a malonic-ester rxn both ways and see how the yields compare.
After that do what you think is best. I'm not the ethanol police.roamingnome - 11-1-2007 at 14:50
im not trying to break the azeotrope in my tall column,
just get 95% alcohol fuel without that much hassel...... of redistilling and wasting energy etc....., but im too impatient to have it drip drip all
day... i want the juice....
i have a few tricks left for the amatrures to beat down the super companies..how about molten nitrate salt bath and a giant super magnifying glass...
boi
i wish i had free feed stock... its a loop hole, when more people grab for it it will become not free... like waste oil from restaurants, Now they
are making money off it, not that "ahead of his time cool guy with a VW rabbit"Fleaker - 11-1-2007 at 17:14
Ah Sauron, I see now. I thought you meant taking it from 95% to 100% anhydrous with sodium. That seemed frivolous. If you're using it for organics
work, then yes, distillation with sodium wire is the way to go for absolutely anhydrous ethanol.bereal511 - 11-1-2007 at 17:21
Quote:
i have a few tricks left for the amatrures to beat down the super companies..how about molten nitrate salt bath and a giant super magnifying glass...
boi
That would make for an interesting project...run a line of molten nitrates through a distillation setup that's melted with a large Fresnel lens.
Though I feel that one would need quite an extremely big Fresnel lens to do the job of heating enough nitrate salts for effective ethanol distilling.
Has there been anyone that's used a solar concentrator to run a distillation rig?Sauron - 11-1-2007 at 18:51
@roaminggnome, ethanol to mix with gasoline to be used as gasahol must be 100% ethanol not 95% because the water will not be miscible with the
hydrocarbons.
If you want to return to pre-1970s engines of course you can burn straight ethanol (with up to 30-35% water in it) with only trivial low cost
modifications. Which is what was done during WWII then everyone seemed to forget about it afterwards.
When the oil crisis hit in the 70s this coincided pretty much with the more complex engines which will not burn just ethanol or ethanol/water.
Gasahol is a really marginal way to reduce petroleum consumption. Mostly fuel ethanol is a fad and a sop to the agro industry who get huge tax
incentives for investing in this. But it's really a crock.12AX7 - 11-1-2007 at 20:30
Oh, I have a "solar still" set up on a warm spot on our kitchen stove (we have two and this one isn't used much.. small pilot flames warm the top
surface enough to be mildly useful). HDPE jug with a reciever hanging from wire and plastic draped over the top, held in place with a rubber band,
and filled with water to gain some cooling (and to keep the plastic settled down!).
Doesn't get too much strength EtOH per stage, and the long time leads to oxidation of the mash. Not a problem as I'm not interested in drinking the
swill...
Timroamingnome - 12-1-2007 at 11:27
yes, ill add the pdf to the pot
after oil the only option is nuclear or solar, so nuclear is for the big boys
the reality of getting the nitrate salt was a hassle, with trucking charges etc....
i still need at least 200 lbs of potassium salt to form the right eutectic blend... nothing is free thats for sure.... but i hope it lasts a long
time...
******
so your "solar still" is gleaning EM radiation of the stove i take it... or just evapaoration rate of the mash... hmmm the problem with adding
fresnel lenses is they have to point directly at the sun to be useful for you...
******
and sauron you dont seem to empressed with alcohol fuel and i do realize the current limitations, but how about genetically modified yeast to go over
the 10-12% ethanol limit, and the holy grail of celluose ethanol.... surely theres some potentional there
i guesss oil will be around for our lifetime so screw worrying to much over it...
*******
@saad are you still into stilling alcohol or what? its as easy as ORG says, but it can be as advanced as suaron elaborates.Chris The Great - 12-1-2007 at 20:31
The azeotrope dissappears when distilling under vacuum, but you'll need some extremely cold coolant flowing through your condenser and cooling the
receiver.Sauron - 12-1-2007 at 20:58
I used to buy yeast in packs about 200 at a time from a guy in Malmo named Gert who is very well known in Scandinavian bootlegger circles, he has
yearsts that will produce 16-20% if you can control the temperature properly. GMO yeasts with still higher yields, maybe someday. Biomass ethanol,
looks like a boondoggle. Look at all the energy expended in collecting and transporting the feedstocks.
Basically, when we talk about ethanol fuel we are talking about converting agricultural land from producing food to producing fuel. In a world with
too many starving people I do not see that as a truly appropriate direction for policy or technology.
It has political sex appeal as a sop to the agro sector. It appeals to buzzwords like "renewable" and "green". but it will always be marginal relative
to oil/fossil fuels. Particularly if you are talking about gasahol which is at best 5-10% ethanol (usually 5%). A 5% reduction is marginal.
Barring some pie in the sky techno breakthroughs, there is simply going to have to be in the course of this century a paradigm shift away from
personal transportation, I mean the automobile. Or a replacement of the internal combustion engine with something else. Something that does not
consume fossil fiels and does not pollute.
I put my money where my mouth is. I never learned to drive. I never owned a car and still do not own one. My wife does not own a car. If we need
transport we call a taxi, and the taxis in Bangkok (all of Thailand) all burn CNG not petrol. Thailand is filthy with natural gas but has little oil.
I know that makes me an eccentric but at least I am not a hypocrite. BTW taxis are very cheap in Thailand.Sauron - 12-1-2007 at 21:12
A buddy of mine is an engineer with one of the seven sisters, now works on tech transfer. His opinion FWIIW is that for the foreseeable future
alternative energy will mean about 10-20 different technologies, each of them marginal, each amounting to a few % of energy needs, but collectively
replacing 15-35% of fossil fuel use. IMO still marginal. Obviously costs will continue to rise as resources continue to dwindle. That will mean market
forces will inevitably come into play and consumption patterns will as a result have to change.
Expect urban design and organization to change. People will telecommute or live at where they work or close to where they work. More mass transit less
personal. We will still depend on trucking but rail may make a comeback.
We will have no alternative but to turn to increased use of nuclear power. Given the rate of consumption of mined uranium ores we either need to
commercialize seawater extraction or go to a Pu economy (fast breeders) with all its implications. No choice at all. The Japanese know this. Of all
the people in the world they have the most reason to loathe nuclear power but they have as a nation wholeheartedly embraced it for entirely pragmatic
reasons.Sauron - 12-1-2007 at 21:20
@Chris the Great, define cold coolant.
My recirculating chiller handles 0 C. There are recirculators that can handle -25 C or below (obviously not with water.)
Dewar condensers, dry ice/alcohol or dry ice/acetone now we are talking -60 to -73 C.
A CO2 cylinder with a dip tube and a nozzle makes dry ice snow in a sack very nicely. There's a commercial kit for this at about $120.
So what temperature are we talking? The coolant should be c.20 C cooler than the cphase change to liquid at the pressure required.neutrino - 13-1-2007 at 13:12
>1. Zeolites (Molecular sieves) selecting the particular one that is best for removing H2O (4A I think.)
No, 3A.
4A sieves have spaces large enough to trap ethanol molecules as well as water molecules. 3A sieves only absorb water because the ethanol molecule is
too big to fit.
You can buy dry ice from some grocery stores. A safeway near me sells it for $1 / lb. Sauron - 13-1-2007 at 14:58
