MagicJigPipe
International Hazard
Posts: 1554
Registered: 19-9-2007
Location: USA
Member Is Offline
Mood: Suspicious
|
|
3-Ball (300 mm) Snyder Vs 400 mm Straight Stainless Packed Column for EtOH/Water Separation
Currently I’m using the 24/40 Snyder column for this (EtOH conc. Is probably around 15%) and so far I’ve only pulled off what appears by smell to
be various fruity smelling ethyl esters and higher alcohols. Of course this EtOH was obtained from yeast/sucrose metabolism. It appears to be working
well but I’d like to avoid all the trial and error if I can so maybe someone could advise which column I should be using to obtain the highest
possible EtOH concentration in the rec. flask on the first run. This would normally be a pretty easy choice but I have ZERO experience with Snyder
columns other than knowing they’re not usually used for basic fractional distillations like this. For example, does the supposedly enhanced
vapor/liquid contact offset the shorter column and less condensing surface area?
Thanks!
EDIT: And to add to this question: the separation of n-hexane from the other isomers? I wonder what sort of separation I should expect after a single
distillation of mixed hexanes? I wonder how much pentane and heptane are in “industrial” hexane?
[Edited on 6-30-2018 by MagicJigPipe]
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
|
|
|
MagicJigPipe
International Hazard
Posts: 1554
Registered: 19-9-2007
Location: USA
Member Is Offline
Mood: Suspicious
|
|
Well, I tried it with the Snyder column. The fraction I saved was from 78°C to 82°C. First, it smelled badly of rubber until I added a piece of
copper wire overnight. But now it smells like really strong wine. I guess I should’ve started collecting later. Smells nothing like 95% EtOH,
that’s for sure.
I’m thinking of collecting up to 85°C and redistilling through the packed column.
Update: ran it through charcoal and now it smells just like 80+% EtOH with hints of esters and higher alcohols. Actually, quite a bit more tolerable
than straight EtOH. I may run it through again.
[Edited on 6-30-2018 by MagicJigPipe]
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
|
|
|
Boffis
International Hazard
Posts: 1879
Registered: 1-5-2011
Member Is Offline
Mood: No Mood
|
|
I had not heard of a synder column before so I had to look it up. I have a similar column but here they are called vigreux columns I think. Anyway
they are not that efficient for low boiling compounds in mixtures so dilute.
When I used to make my own ethanol I fermented 1kg of white sugar, 150g molasses, 1 heaped teaspoon of citric or tartaric acid (about 10-12g) and 1
heaped teaspoon full of ammonium phosphate. This ferments very quickly to about 12% alcohol. I then settled the yeast, decanted and pot distilled in
batches of about 2L in a metal still. I would collect about 600-650ml of distillate from each batch. When I had 4 batches I would pot distil it a
second time and collect everything up to about 87-88 C and a second cut up to about 95 C. The second sut was added back to the next batch and the
first cut fractionally distilled using a 55cm tall column packed with glass rings. Very slow distillation was used to obtain a good separation of the
fraction that passed over below about 76 C, then a fraction boiling between 76 and 82 C. The residue was distilled quickly up to about 90 C and added
to the next batch. The small amount of residue in the glass flask was discarded. It takes two further such fractionations with increasingly tight
"cuts" with my equipment to obtain constant boiling point rectified spirit. The yield on a single batch basis was about 1.6l of RS from 22l (5
imperial gallons) of fermented sugar solution. However this is raised to about 2l over time by constantly reworking the higher and lower boiling
fractions.
One last point to remember is that I live almost at sea level but even here variation in barometric pressure can change the boiling point of the
azeotrope by about 3 C between normal high and low pressure days so when you "cut" is only 3-4 C wide range you need to take this into account on the
day. You also need to take into account your elevation; there is plenty of data on this on the internet.
|
|
|
Sulaiman
International Hazard
Posts: 3723
Registered: 8-2-2015
Location: 3rd rock from the sun
Member Is Offline
|
|
I have neither Snyder nor Vigreaux columns but I know that they are different,
I'd expect a 3-ball Snyder column to be about three 'plates'
I believe a typical Vigreaux is one to two 'plates'
Whereas an insulated 400mm packed column with a reflux condenser could be around ten 'plates'
= from mash to almost azeotropic.... no contest.
My favourite EtOH information source https://homedistiller.org/
CAUTION : Hobby Chemist, not Professional or even Amateur
|
|
|
SWIM
National Hazard
Posts: 970
Registered: 3-9-2017
Member Is Offline
|
|
I usually just distill alcohol to 85 or 90% and then add potassium carbonate (at least 10% by volume).
It draws the water out of the solution and makes a 2-phase situation where the top is 95% ethanol and the bottom layer is water and carbonate with
little if any ethanol left.
Just decant, and re-distill if necessary.
Treat with calcium oxide (either refluxing, or long digestion with occasional shaking)before the re-distillation to get the water level down to 1% or
so.
Doing the calcium oxide thing twice is a good idea.
If you need it REALLY dry, have a look at Magpie's thread on drying ethanol.
I have used Snyders a bit, and think they might actually be better than one would expect from the number of valves.
However I have never tried to do a direct comparison with other columns, and may be being unduly influenced by the fact that Snyders do that bubbling
and clinking thing which is really pretty cool to watch compared to most other columns.
|
|
|
S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline
Mood: Enhanced
|
|
Maybe you don't really want your crudest product refluxing for a long time while being carefully fractionated. I'd clean it up first as quick and cold
as possible, then reflux with KOH for as long as that causes color. Copper scrubbers or stainless steel turnings are effective when used correctly;
perhaps the Snyder is reliable when there are a lot of sections for the height, but usually no they're cheaply made.
|
|
|
happyfooddance
National Hazard
Posts: 530
Registered: 9-11-2017
Location: Los Angeles, Ca.
Member Is Offline
Mood: No Mood
|
|
This part. That is why a stripping run is a stripping run.
Plus you are then working with a much smaller volume when you finally are doing the real fractionating.
O.P. is asking about column sizes yet doesn't mention the size of his boiling pot... How could anyone make a suggestion? (I noticed no one has) The
choice of column type and size is directly related to the amount of liquid in the boiling pot.
Glad he finally got it figured out. That carbon works wonders. So does a little salt in the boiling pot.
Homedistiller.org does have some great info.
|
|
|
MJ101
Hazard to Self
Posts: 82
Registered: 14-6-2018
Member Is Offline
Mood: Always Sunny
|
|
@happyfooddance: Thanks for posting that link. 
A lot of great information there, especially for DIY folks.
The relationship between the pot size and the column size is also pointed out there.
I found this page informative and amusing:
https://homedistiller.org/intro/bad
[Edited on 6-7-2018 by MJ101]
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
