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Author: Subject: pharma / food grade ethanol - distillation using Hempel column
Fery
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[*] posted on 21-4-2021 at 11:11
pharma / food grade ethanol - distillation using Hempel column


In spring 2020 I collected 10 kg apples which fall to the ground in an abandoned apple orchard. I processed them using blender, added 7 kg beetroot sugar and water so the volume was 40 L and let it to ferment. When fermentation finished and CO2 evolution stopped, I divided the cider into 3 portions and distilled it using my 20 L stainless steel kettle which I use also for mentha piperita hydrodistillation. I did not made photos as there is nothing special, the photo of the apparatus is in the thread with hydrodistillation. I performed the distillation during winter while burning wood in my stove to heat the house, so it did not cost extra energies like electricity / gas. I got 3 portions of 3 L so together approximately 9 L of 35-40 vol % product (the apparatus has some very simple and not too much efficient column/head. Then I distilled it at once for the second time using the same pot, it yielded cca 4,5 L 75-80 vol % concentration. Again nothing special.
Now it was the right time to perform final distillation. As I have 6 L RBF it would fit into it but my largest heating mantle is designed for 4 L flask. So I had to divide it into halves and perform the final distillation twice. I did not want to distill on wood stove as the heating power is not steady. I did not want to distill on gas stove because of the risk of fire if the flask breaks (well, I could use big pot with oil bath but I do not have such a big pot and there is also not enough room above my gas stove upto the ceiling, the tallness of the whole apparatus is 1,8 m).
So I put the 75-80 % alcohol into 4 L RBF, then assembled 1 m high 30 mm inner diameter Hempel column packed with 6-10 mm Raschig rings, head for taking off reflux at desired ratio, collecting flask. I greased the stopcock with as little as possible of food grade grease Lukosan M 14. I insulated the column by approx 10 layers crumpled newspaper (keeps more air which is the insulator when compared with flat newspaper) and finally aluminium foil layer so it was more airtight (newspaper is not too much airtight). Well it does not compare to vacuum jacketed column, but I do not have such insulated column. The unjacketed column was not much expensive, IIRC it cost only somewhat like 20 EUR.
The main fraction distilled at 77,25-77,5 C (lit. 78,2 C azeotrope) and water distilled at 99,5 C (lower air pressure, overcasted, little rain).
Photos from the process follow and also short video here
https://youtu.be/0wMHckg64iA



on the 1st picture the flask with attached column, 2nd detail of packing with Raschig rings which were wetted with the distilled liquid by pouring the liquid into the apparatus from the top of the column, 3rd on the flask bottom there are red/brown boiling stones and the flask is already filled with the liquid to be distilled
IMG_20210421_095912_1_sm.jpg - 33kB IMG_20210421_095938_7_sm.jpg - 33kB IMG_20210421_101503_9_sm.jpg - 20kB



1st column insulated with approx 10 layers of crumpled newspaper, 2nd final aluminium foil to at least somewhat increase airtightness, 3rd fully assembled and filled apparatus
IMG_20210421_103650_3_sm.jpg - 36kB IMG_20210421_104439_6_sm.jpg - 40kB IMG_20210421_104502_7_sm.jpg - 32kB



1st also the flask was insulated with newspaper, 2nd condensate already dropping in the regulated reflux ratio distillation head, 3rd the T was initially high as the column was wetted with the liquid to be distilled
IMG_20210421_110437_5_sm.jpg - 42kB IMG_20210421_110751_7_sm.jpg - 37kB IMG_20210421_110957_7_sm.jpg - 22kB



1st column flooding at which the heat power was reduced so the column later did not flood and the speed of reflux returning was as high as possible (the higher reflux amount returned into the column, the better separation during distillation, but the column must not flood), 2nd T falling slowly, 3rd column not flooding, stopcock still closed
IMG_20210421_111021_2_sm.jpg - 30kB IMG_20210421_112034_7_sm.jpg - 21kB IMG_20210421_112412_0_sm.jpg - 41kB



1st minimal T reached, T 74,0 C and does not fall anymore, after 30 minutes the equilibrium in column already established, 2nd and 3rd the stopcock slightly opened, so approx 1 drop taken into the collecting flask and 9 drops returning back into the column
IMG_20210421_113139_9_sm.jpg - 23kB IMG_20210421_113432_1_sm.jpg - 35kB IMG_20210421_113434_4_sm.jpg - 35kB



1st forerun collected in a small 100 ml flask, 2nd T raising, actually 75,25 C, 3rd T rasing, actually 76 C
IMG_20210421_113532_2_sm.jpg - 27kB IMG_20210421_113604_7_sm.jpg - 24kB IMG_20210421_114101_3_sm.jpg - 24kB



1st and 2nd drops of condensate collected in small flask (forerun), 3rd T raising, actually 76,5 C
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1st T 77,0 C, 2nd still collecting forerun, T reached 77,25 C at which it did not raise anymore, I collected 100 ml of extra forerun at this T to certainly remove all methanol during which the T kept stable at 77,25 C, 3rd switched the collecting flask from small 100 ml into 1 L RBF, the main fraction distilled in T range 77,25-77,5 C (low atmospheric pressure caused by weather conditions - overcast, occasional slight rain)
IMG_20210421_120728_9_sm.jpg - 24kB IMG_20210421_120734_7_sm.jpg - 33kB IMG_20210421_133744_3_sm.jpg - 49kB



more photos will follow, I had to split due to limitation of number of photos in 1 post




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Fery
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[*] posted on 21-4-2021 at 11:27


here how quick the T changed when the main fraction distilled, every picture name contains its exact date and time
now collecting afterrun and finally determining the boiling point of pure water as the atmospheric pressure was below normal (caused by weather conditions)
the main fraction distilled at 77,25-77,5 C, I managed to capture the quick T raising with the afterrun fraction



17:07:09 T 78,0 C, 17:07:29 T 78,25 C, 17:07:43 T 78,5 C
IMG_20210421_170709_2_sm.jpg - 25kB IMG_20210421_170729_5_sm.jpg - 24kB IMG_20210421_170743_2_sm.jpg - 25kB



17:08:03 T 78,75 C, 17:08:12 T 79,0 C, 17:08:26 T 79,5 C
IMG_20210421_170803_3_sm.jpg - 21kB IMG_20210421_170812_1_sm.jpg - 23kB IMG_20210421_170826_2_sm.jpg - 23kB



17:08:39 T 80,0 C, 17:08:47 T 80,25 C, 17:08:53 T 80,5 C
IMG_20210421_170839_5_sm.jpg - 24kB IMG_20210421_170847_8_sm.jpg - 24kB IMG_20210421_170853_3_sm.jpg - 23kB



17:08:58 T 80,75 C, 17:09:02 T 81,0 C, 17:20:32 T 99,5 C water distilling after collecting the whole afterrun, T does not raise anymore, low atmospheric pressure caused by weather conditions
IMG_20210421_170858_9_sm.jpg - 24kB IMG_20210421_170902_9_sm.jpg - 22kB IMG_20210421_172032_4_sm.jpg - 21kB




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[*] posted on 21-4-2021 at 13:30


Could you include a few more pictures of a thermometer reading nearly 80C?
:-)
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[*] posted on 22-4-2021 at 12:04


nice column, very nice take-off head !

I don't trust alcohol thermometers long term and
maybe immersing the thermometer more would give a more accurate reading ?
(or was it just local atmospheric pressure ?)




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[*] posted on 22-4-2021 at 22:49


I got better idea for thermal insulation of the column. In every shop supplying plumbers there are thermal insulation tubes (plastic material with a lot of small air bubbles) of various internal diameters and wall thickness, they are used to insulate water tubes etc. I'm not sure whether they withstand 100 C at the end of distillation. So maybe cover the glass column with few layers of newspaper + aluminium foil (in case plastic insulation melts) and then cover that with insulation tube from plumbing shop. They are 2 m long which is much more than my longest distillation column.
Sulaiman - it was local atmospheric pressure. I'm living at altitude 430 m above sea level and that day the air pressure was lower due to weather conditions. I checked that water boils at 99,6 C when atm. pressure 99,8 kPa instead of standard 100,0 C at 101,3 kPa.
For ethanol the boiling point change could be also calculated (IIRC Clausius-Clapeyron equation). But even without calculation, the T stayed in range narrower than 0,25 C for the whole main fraction. You do not need to calculate the T difference to watch when T reaches it, by my experience it is enough to watch the thermometer without knowing the exact b.p. I was distilling 2 liters so when T does not increase (I was able to determine T change 0,25 C by my thermometer) during collecting 50 ml of distillate you are at the right temperature and you should collect the main fraction. Removing extra 50 ml from the beginning has negligible impact on yield at scale 2 L and is also good to remove as much methanol as possible. I will send samples to my friend Bedlasky who will determine methanol content, he has access to gas chromatography. Boiling point of the main fraction +- 1 C may be caused by the altitude and weather changing atmospheric pressure. I distilled the second half the next day and at the end of distillation water distilled exactly at 100,0 C (better weather and normal atmospheric pressure that day). I won't post pictures of the second day distillation when T was around 80 C and later 100,0 C according unionised suggestion.
There is a norm for thermometer producers in my country so they must write to the thermometer stem a value how much millimeters the thermometer bulb should be inserted for thermometers without ground glass joint. All heads and distillation adapters which are made in my country are for 40 mm insertion length of thermometers with ground glass joint (40 mm is the length of thermometer bulb and stem measured without the length of ground glass joint 14/23) - all these glassware pieces are compatible with these 40 mm ground glass joint 14/23 thermometers. Also the 10th and 12th picture in my initial post show the position of thermometer bulb which is ideal.




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[*] posted on 22-4-2021 at 23:17


I have used those tube foam insulator wraps and they are great.

The concept of that still is same as bokakob. It works great.
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[*] posted on 22-4-2021 at 23:21


I'm used to 75mm (3") immersion depth which makes 40mm look wrong to me,
but 40mm is more practical for small scale glassware than 75mm.

At home (UK) I use this stuff https://www.paroc.co.uk/products/technical-insulations/pipe-...
but here I've been using microfiber cloth + Al foil for column insulation.




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[*] posted on 1-5-2021 at 00:47


My friend Bedlasky performed GC analysis and methanol was below 0,1%, higher alcohols below 0,03%, ethyl acetate below 0,005% in every sample (I sent him 3 samples from the 2 distillations, both distillations yielded approx. 2x1,4 L of ethanol, first 1 L stored in a 1 L flask - sample 1., sample 2. and last approx 2x0,4 liters merged and stored in the third 1 L flask - sample 3).
I was very afraid of methanol as I used 10 kg apples fallen to the ground/grass as a source of yeast + minerals + organic substances for yeast. To increase yield of ethanol I used sale-out sugar from supermarket. Apples are reach in pectins and fermentation of methylated pectins yields methanol. I rather let this ethanol for my future pharma / food purposes (like tinctures etc) and eventually purify petrochemical ethanol for my syntheses (remove denaturing agents MEK and bitrex).




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[*] posted on 1-5-2021 at 03:37


Homedistiller has investigated this thoroughly, and the methanol is trivial to separate from ethanol even with smaller reflux fractionating column.

I have concluded that there are no known cases of methanol poisonings from fermentation based moonshines. They all derive from added technical alcohols to cut costs.

I do indeed suggest using otc ethanol sources for synthesis. It's significantly cheaper and can be easily purified, depending on purpose, from technical to even into potable form. Fermentation is extremely long and arduous process, and really works well only in larger scale. For drinking purposes, 50L boilers tend to be minimum, as single strip&frac can deliver only about 3-4L of azeotropic high quality potable alcohol. Considering that you need vats to ferment it for at least a week + few days for clarification, then strip it to 50% and then fractionate over several hours to recover the foreshots, heads, hearts and tails. Of these, you recover about 50-60% at max if you want the high quality only without off taste. Even then, sitting on activated carbon for couple of weeks at 50% dilution will improve the profile noticeably.

Instead, you go to shop, buy 10L canister of ethanol for 20€ and simple distill it at full rate to recover almost 9 liters of azeotropic ethanol with little MEK in few hours. Add some NaOH, and the MEK is also gone. Distilling it twice and sitting on carbon has made it potable to some of the more sippy chemists.

[Edited on 1-5-2021 by Fyndium]
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[*] posted on 1-5-2021 at 07:42


Fyndium 1 L tech. ethanol costed here 50 CZK before virus, then producers/sellers/resellers abused the situation so the price skyrocketed to 3 fold and not only price but it was also unavailable together with isopropanol. There are still some sellers which sell it at such high price although no such demand for disinfectants and ethanol and isopropanol already returned to the lists of eshops.
https://www.funchem.cz/www-funchem-cz/eshop/2-1-ORGANICKE-LA...
1 L for 149 CZK, still threefold price. Maybe they stocked a lot of it it 1 year ago while the prices were too high so they have to sell it so overpriced.
I can produce 1 L of ethanol from 2 kgs of sugar which I can buy for 2x7,90 CZK = 16 CZK in supermarket sales-out which is 3-times cheaper than the price of synthetic ethanol before SARS-CoV-2 (50 CZK). You can approximate 50 CZK = 2 EUR = 2,30 US$. During winter when heating my house by burning wood in a stove it does not cost extra energy, just putting the still to the stove. So processing the large volumes of diluted ethanol requires only some work and does not cost me any money. Only the final column distillation does require electrical or gas heating as the wood heating is not steady.
Moreover in my ethanol there is no shit like 1,6 % methylethylketone either denatonium benzoate.
For removing MEK using NaOH you need an old flask for which you do not bother etching glass by hot NaOH. I certainly wouldn't use new shiny glass flask for that.
Even homemade distillates which may contain upto 1% of methanol (you can't simply distill on column as that would also strip off not only methanol but also all aroma) do not cause acute methanol poisoning as the poisonous substances are formaldehyde and formic acid which are made from methanol by liver alcohol dehydrogenase which is competitively processing ethanol in large excess.
I also wanted low methanol content for the case of esterification.
According technical ethanol I was thinking of fuel E85 which you can buy at some petrol stations - the ethanol content is 85% and the 15% is gasoline, the cost of this fuel is approximately 1 US$ for 1 L. It would avoid etching flask with NaOH as there is no MEK, moreover the alkanes content would remove all water as azeotrope during distillation, so the obtained ethanol would be close to anhydrous.
Maybe my 1 m long 30 mm diameter column packed with small Raschig rings would be sufficient to separate azeotr. ethanol from MEK (b.p. 78,2 C vs 79,6 C) but such distillation would require certainly something like at least 20 theoretical plates so only then I won't need to use NaOH for MEK aldol condensation?




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[*] posted on 1-5-2021 at 09:10


Fery: Very nice work!

1l bottle of ethanol from Severochema cost somewhere between 75-85 CZK, depending on the shop. 149 CZK is heavily overpriced.

[Edited on 1-5-2021 by Bedlasky]




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