Molecular Sieve Distilling

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Molecular Sieve Distilling

Postby dr wacky » Sat Aug 12, 2006 9:21 am

When distilling ethanol for use in making biodiesel or E85, I know it has
to be very dry(199-200 proof). Filtering your high-proof distilate through
a molecular sieve will accomplish this drying effect. Now here comes the
stupid question. If you read any further and are offended at my ignorance,
you were warned.

What would stop a fellow from just filtering his whole wash through a
molecular sieve to achieve ethanol separation? I can see a couple of
drawbacks to this idea. You would have to sieve many times to achieve
any purity(10, 15, 20 ). Seems it would depend on the alcohol content of
the wash, volume of wash, and size of the sieve. You would also have no
way to make 'cuts'. But in a fuel application, that really shouldn't matter.

This isn't how I plan to do my real distilling, but I may experiment with
a small test batch or two just to see if it's possible. Anyone willing to point
out a glaring oversight in this process?
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Postby J0HNmhs » Sun Aug 13, 2006 10:24 am

I am sorry i cant answer your question but where and how did you come across a molecular sieve? Also what was the cost??
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Postby Big J » Sun Aug 13, 2006 11:43 am

I don't know much about molecular sieves but I came across this on ebay:
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... gory=57114

"This listing is for Zeolite. Zeolite is a molecular seive that you use to dry out alcohol, specifically for ethanol fuel production. the reason you need zeolite is that the best any still can general do is 180 to 190 proof (90-95%) and you can actually get more alcohol out of your batch if you run a slightly lower proof. The remaining 5% to 10% is water which you can't put into your car as it will hurt your engine. so what you do is you take zeolite, which is called a molecular seive, and you strain out the water at the molecular level. Zeolite is similar to kitty litter. You put the zeolite in a bucket, you put ethanol in a bucket, and the zeolite absorbs the water from the ethanol. It can hold about 22% of its weight in water (i.e. 1 lb of zeolite absorbs .22lb of water). Zeolite is reusable, you just dry the zeolite out by heating it and then you can reuse it again and again. The zeolite I have listed is type 3a and it is the small mesh size so that it absorbs the water quicker. This listing is for a 5 pound can of it. If you need 10 lbs you would have to buy two cans. If you want more than 2 cans please let me know your zip code and I'll make a custom listing for you with reasonable shipping. If you have any other questions please let me know. No returns once package is opened."

-J
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Postby Big J » Sun Aug 13, 2006 11:57 am

Just doing some quick math:

25lbs of zeolite (11.33 kg) could absorb 2.5L of water (if the 22% the guy quoted above is accurate). So, if you had a 95% ethanol/water mixture, you could use the 11.33 kg of the zeolite on 50L of your distillate. Does anyone have any experience using this stuff? I wonder how long it takes or if it takes any more effort/technique than just dumping the zeolite in with your distillate.

Cheers,
J
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Postby AllanD » Sun Aug 13, 2006 1:18 pm

The problem is how much energy it takes to drive the water out of the "molecular seive" each time it's used and the need to expend the
energy repeatedly....

AD
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Postby AfricaUnite » Sun Aug 13, 2006 2:33 pm

My question is once you dry the alcohol, wouldnt contact with the air bring it back to 96.wahtever the decimal is? Otherwise I think this is a very good item (thanks for the link) for small scale ethanol production.
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Postby maze48 » Sun Aug 13, 2006 5:20 pm

Big J wrote:Just doing some quick math:

25lbs of zeolite (11.33 kg) could absorb 2.5L of water (if the 22% the guy quoted above is accurate). So, if you had a 95% ethanol/water mixture, you could use the 11.33 kg of the zeolite on 50L of your distillate. Does anyone have any experience using this stuff? I wonder how long it takes or if it takes any more effort/technique than just dumping the zeolite in with your distillate.

Cheers,
J


I've used zeolite in small batches. I just put about 5lbs. of zeolite in a 5gal. bucket, then pour the ethanol over it. Let it set overnite then pour the "dried" ethanol out into a container. I use it mostly in small 4 stroke engines.

To dry it out I put it into a preheated oven, at about 350 F. Hold it for about an hour then let cool and take out. You can use a solar oven to do this but, I haven't built one as yet.

Make sure you put the dried zeolite into a plastic jar or bag that is air tight. This stuff will grab moisture from the air around it. Especially humid parts of the country.

I've read that you can use rock salt as a seive, but haven't done any research yet.
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Postby Rebel_Yell » Sun Aug 13, 2006 5:33 pm

???

How do the big distillers make ethanol for fuel????

Distill to as high abv percent as possible. Then use other means to reduce the water content.

Why? Economics... This is the cheapest way.
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Postby The Chemist » Sat Aug 19, 2006 4:04 pm

Reb's right. The reason is that, while zeolites are great for removing water from an "ethanol and not much else" mixture, they will do nothing to get rid of things like proteins, sugars, waxes, steroids, etc...that are in a wash.
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Postby hornedrhodent » Sun Aug 20, 2006 3:31 am

It's not really molecular seiving though - more like using a substance with a chemical affinity for water to suck it out of the ethanol. (eg quicklime,starch or silica gel)

My idea of a molecular seive would be something like forcing it through a reverse osmosis membrane.
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Postby blacksmith » Sun Aug 20, 2006 5:55 pm

Here is a place that sells the stuff.
http://www.deltaadsorbents.com/catalog.asp
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Postby dixiedrifter » Mon Aug 21, 2006 11:55 pm

Acutally molecular sieves ARE molecular sieves.

A molecular sieve consists of a sodium alumino silicate (IIRC) crystaline matrix where the spaces between the crystals are a certain uniform size.

In the case of 3A, the spaces are 3 angstroms. Due to osmotic pressure water (and whatever else is smaller than 3 angstroms) is essentially forced into the sieve. Type 3A is what is commonly used to dry ethanol and methanol.

Type 4A (IIRC) is the potassium based version, and due to the larger pore size will absorb both ethanol and methanol. Type 4A is commonly used used in the laboratory for drying solvents such as ether and tetrahydrofuran.

Anyhoos, it would be great if one could just suck out all the moisture in alcohol using molecular sieves. But, they simply don't hold enough moisture and are too much of a PITA to properly regenerate. Plus your left over with whatever in your alcohol that the sieve did not absorb.

So, for all intents and purposes that means pre-distillation is a must.
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Postby hornedrhodent » Tue Aug 22, 2006 2:36 am

dixiedrifter wrote:
Acutally molecular sieves ARE molecular sieves.

A molecular sieve consists of a sodium alumino silicate (IIRC) crystaline matrix where the spaces between the crystals are a certain uniform size.

In the case of 3A, the spaces are 3 angstroms. Due to osmotic pressure water (and whatever else is smaller than 3 angstroms) is essentially forced into the sieve. Type 3A is what is commonly used to dry ethanol and methanol.

Type 4A (IIRC) is the potassium based version, and due to the larger pore size will absorb both ethanol and methanol. Type 4A is commonly used used in the laboratory for drying solvents such as ether and tetrahydrofuran.

Anyhoos, it would be great if one could just suck out all the moisture in alcohol using molecular sieves. But, they simply don't hold enough moisture and are too much of a PITA to properly regenerate. Plus your left over with whatever in your alcohol that the sieve did not absorb.

So, for all intents and purposes that means pre-distillation is a must.




Sounds more like a molecular sponge than the sort of seive I uses to let through small stuff an keeps back larger stuff - unless it's a single membrane rather than a powder.

Anyway names of products dont necessarily mean what they say. I'd better just accept the conventional usage.

Thanks for the explanation dd. :wink:
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Postby lbrombach » Fri Jul 20, 2007 3:46 pm

Sorry to be the new guy that drags up old topics, but I thought I could shed some light on the subject. I did all this because I asked myself the same question a while back and had to work it out anyway. Hope somone finds it informative.

I found on a distibuters site where it take 1800 btus per lb to get the water out of the 3a zeolite. so if you had 10 gallons of a 10% mash you'de have to adsorb 9 gallons of water. To drive this out of the zeolite:

9gal X 8.33lbs/gal X 1800btu = 135,000 btus

now, to distill the same mash we have to:
raise the temp of 10 gallons of mash say...120 degrees, then boil off the ethanol (at 361 btus/lb). then dry about .3 gallons of water out of the zeolite. So:

10gal X 8.33 lb/gal X 120deg = 9996 btus for "sensible heat"

AND

6.6 lb (per gal of etoh) X 361 btu = 2382 latent heat of etoh

AND

.3 gal X 8.33 lb/gal X 1800btu = 4498 btu for drying

add them together and get not quite 17000 btus, or about 1/8 the amount of energy to dry the zeolite if that is our sole source of drying the mash.


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Postby Husker » Fri Jul 20, 2007 4:36 pm

There IS a new still out there, a ROPEM (Reverse Osmosis, Personal Ethanol Machine).

Here is a description:

http://www.beutilityfree.com/still_home ... tills.html

There are people (not the company making it), that are getting one for testing. The current problem appears to be getting the actual machine, so right now, I have no real information, other than the web "add".

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Postby The Chemist » Sat Jul 21, 2007 3:57 pm

I saw this (ROPEM) in the other thread, and the problem I have with it is the same I mentioned above: there's other crap in the wash that you don't want in your booze.

Also, reverse osmosis systems generate, like, twenty times the volume of the the "product" stream (which would be the water in this case) in the "waste" stream (which would be the booze). I don't see how you would overcome this without endless recirculation.
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Postby Husker » Sat Jul 21, 2007 11:45 pm

The Chemist wrote:I saw this (ROPEM) in the other thread, and the problem I have with it is the same I mentioned above: there's other crap in the wash that you don't want in your booze.

Also, reverse osmosis systems generate, like, twenty times the volume of the the "product" stream (which would be the water in this case) in the "waste" stream (which would be the booze). I don't see how you would overcome this without endless recirculation.


Yes, the ROPEM is for fuel. Without the still to "properly" fractionate your product, you concentrate other things also.

By my reading of it, the whole thing recirculates a lot. Each time the EtOH gets stronger/stronger.

There are 4 sieves (and some pre-filtering) in the system. The last 2 "sieves" are a 5 angstrom, and 3 angstrom. The 5, allows both EtOH and H2O to pass. The 3, only allows H2o. For the higher and lower alcohols, I do not know their molecular size, thus, which ones get trapped in the <5> 3 range, I do not know.

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Postby Red Eye Rising » Tue Nov 20, 2007 9:26 am

55 gal drums of ground corn will take 95 to 100 IF you pump the fuel UP through the ground corn real slow. The corn soaks the water and fuel and lets go of the fuel easier. Measure the fuel out and stop at 98.2 Flush the remainder out with wash and run again. When the corn has been flushed it can be used for a mash base. Use three drums. Replace the first in line with the second and add a fresh for the first. Flush the one replaced. Obviously you need lids and bands on them drums.



No loss of fuel.
Higher %wash to run from flush.
Use the corn again for a new mash.
Good for the environemnt.
No wasted heat drying sieves.
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Postby Husker » Tue Nov 20, 2007 12:19 pm

Red Eye Rising wrote:55 gal drums of ground corn will take 95 to 100 IF you pump the fuel UP through the ground corn real slow. The corn soaks the water and fuel and lets go of the fuel easier. Measure the fuel out and stop at 98.2 Flush the remainder out with wash and run again. When the corn has been flushed it can be used for a mash base. Use three drums. Replace the first in line with the second and add a fresh for the first. Flush the one replaced. Obviously you need lids and bands on them drums.

No loss of fuel.
Higher %wash to run from flush.
Use the corn again for a new mash.
Good for the environment.
No wasted heat drying sieves.


How much EtOH can you run through a 55 gallon gound corn? How much dewattered EtOH do you get, and how much is left to be washed out of the grain? If you can push through 350 gallons or so, and get 320 dewatered out, with 10 gallons of EtOH left to be washed out, then this certainly looks like a good method.

Much better than Zeolite. It takes a LOT of energy to remove the water from the zeolite after it does its thing, before you can do it again.

The ROPEM which was talked about a lot in the Yahoo group "alcoholfuels" ended up being a bust. It did not work, and was simply a water RO that was packaged and fraudulently sold to filter out Ethanol. It simply did not work.

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Re: Molecular Sieve Distilling

Postby DSmith78 » Fri Mar 15, 2019 5:56 am

I know this is an old thread but I've just discovered this stuff and looked a little into it, not for any practical purpose just a curiosity thing. Then I considered silica gel. It's non toxic, molecularly similar to quartz crystal, loves drinking water but won't absorb ethanol. Any thoughts?
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Re: Molecular Sieve Distilling

Postby bluefish_dist » Fri Mar 15, 2019 7:15 am

What most people are describing are desiccants. They absorb moisture and lock it up in a substrate. This is one way to dry ethanol. It does work, but I would expect you need far too much if you started with a wash vs a azeo distillate.

Molecular sieves are just filters with really small holes. Like most filters I bet they would plug up if you try and pass a “dirty” wash. It could be done, but would need high pressure and multiple stages to remove the larger particles prior to the last stage of alcohol filtration. Just look at the cost of a ro system and those only filter down to water molecule size. I can see why this would be the preferred method for large scale producers. It’s still probably cheaper to distill first then filter. A lot less volume to filter and less impurities to remove. Besides distillation is well understood and relatively cheap to do.

If you want to try a filtering method, try freeze jacking.
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