LD5050
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Preventing foam formation-steam distillation?
I'm in the process of steam distilling cinnamon bark and collecting the cinnamon oil. The problem is, is that I'm getting a ton of foam forming and
it's boiling out of the flask like a volcano. I ground the cinnamon bark in a coffee grinder to a powder. I loaded this into a two liter RBF and
filled half way with water and set up for simple distillation. Looking back now I realize I shouldn't have ground the bark to Finely. But I'm
wondering if there is something I can do to control the foaming with this batch next batch I won't grind it as much.
Also if anyone has some good tips or pointers on steam distillation I'm all ears.
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mayko
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You might try adding some calcium chloride to the boiling flask; I can't imagine it would impact the cinnamon oil distillation and it might harden the
water enough to reduce the foaming.
(Full disclosure: I break something every time I try a steam distillation)
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Sulaiman
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I've not done steam distillation yet,
but I have noticed that strong stirring usually reduces foaming,
(I guess that stiring bursts bubbles)
I have seen examples of steam distillation using a chromatography reservoir flask http://www.ebay.co.uk/itm/1000ml-24-40-Chromatography-Reserv...
to hold vegetative samples above the steam distillation flask,
molecules are picked up by the steam as it rises,
excess condensed water drains back into the steam generating flask,
so no frothing in the upper flask
and any foaming from the bottom flask gets 'caught' in the upper flask.
Maybe avoiding the need for drying and powdering ?
Wide pathways reduce the foaming problem,
e.g. my 10/14 kit has such narrow pathways that a meniscus of bubble can block pathways completely and be propelled along by the gas/vapour,
whereas my 24/29 kit does not suffer this particular problem.
Worst case - go slowly and don't fill flasks to more than 1/2-full
(or if you are a pessimist, keep the flask more than 1/2-empty 
CAUTION : Hobby Chemist, not Professional or even Amateur
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symboom
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This is a big problem in many synthesis such as making hydrazine sulfate and any acid and carbonate reaction
The terms anti-foam agent and defoamer are often used interchangeably. Commonly used agents are insoluble oils, polydimethylsiloxanes( silicone oil)
and other silicones, certain alcohols, stearates and glycols. The additive is used to prevent formation of foam or is added to break a foam already
formed.
Water based defoamers are different types of oils and waxes dispersed in a water base. The oils are often mineral oil or vegetable oils and the waxes
are long chain fatty alcohol, fatty acid soaps or esters. These are normally best as deaerators, which means they are best at releasing entrained air.
In used such as hydrazine synthysis it might destroy the hydrazine
In industrial processes, foams pose serious problems. They cause defects on surface coatings and prevent the efficient filling of containers.
https://en.m.wikipedia.org/wiki/Defoamer
[Edited on 17-9-2017 by symboom]
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Melgar
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Two readily-available anti-foaming agents are silicone oil and hair conditioner. I have a Dominican-operated pharmacy on my block that has silicone
oil for putting in hair, and it can also be found as a lubricant at many hardware stores. Hair conditioner has cetyl alcohol in it, which is also a
decent foaming agent. It's what I recommend every time I hear that someone put regular dish soap in a dishwasher, and now has a foam volcano to deal
with.
The first step in the process of learning something is admitting that you don't know it already.
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Magpie
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I have just set up to steam distill 9g of cinnamon bark in a 500 ml rbf with Claisen adaptor. 150 ml of water was added to the pot. I'll report back
on any foaming. The bark was ground for 30s to a coarse powder.
[Edited on 18-9-2017 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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JJay
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I have used cetyl alcohol as an anti-foam agent, and it is highly effective. But it is a bit volatile with steam, so you might have to re-distill if
you use it. I'm not sure about silicone oil....
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Magpie
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Severe foaming !!
The single most important condition for a successful synthesis is good mixing - Nicodem
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Magpie
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No foam now. Before the foam had risen up into the neck of the flask. So I removed the heating mantle. Not knowing what else to do the steam
sparge was just coming on so I left it. Now no foam! I'll post a picture when I get to my other computer.
[Edited on 18-9-2017 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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JJay
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Another option would be to hold the cinnamon in a bulb or tube and to run steam through it rather than immersing the cinnamon in water. You can also
buy cassia oil, although it can be a little hard to find at times.
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Melgar
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Quote: Originally posted by JJay  | I have used cetyl alcohol as an anti-foam agent, and it is highly effective. But it is a bit volatile with steam, so you might have to re-distill if
you use it. I'm not sure about silicone oil....
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I'd imagine that silicone oil's volatility would depend on its molecular weight, no?
The first step in the process of learning something is admitting that you don't know it already.
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JJay
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I don't completely understand how steam distillation works, but I think it might have something to do with hydrogen bonding. Obviously heavier
silicone oils would be less volatile than lighter ones ceteris paribus.
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Magpie
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Here's a picture of my set up:
The distillate would not separate into 2 phases even though I attempted to salt out using K2CO3. It smelled strongly of cinnamon.
The single most important condition for a successful synthesis is good mixing - Nicodem
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UC235
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| Quote: Originally posted by Magpie | Here's a picture of my set up:
The distillate would not separate into 2 phases even though I attempted to salt out using K2CO3. It smelled strongly of cinnamon.
|
Oil yield from cinnamon/cassia is supposedly 0.5-1%. With 9g, you can hardly expect <90mg of essential oil to form a distinct layer. Saturate with
NaCl and do a few DCM extractions and be aware that it oxidizes pretty readily.
If you're looking for proof-of-concept essential oil distillations, cloves have an extremely high yield at a reported 14-21%. Eugenol purification
can reportedly carried out by alkali treatment which forms the soluble phenolate salt and saponifies eugenyl acetate to form same. The terpenes remain
insoluble.
I have processed nutmeg before (for trimyristin) and got several ml of EO as a sideproduct from 100g. Reported yield is approximately the same as
cloves. Most other materials have below 5% yield, and the vast majority less than 1%. Other decent candidates at ~5% are cedarwood, allspice, anise
seed, caraway seeds, fennel seed, and frankincense resin.
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JJay
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Benzyl alcohol steam distills in a concentration of 9% with water at 100 C. According to its relative vapor pressure and the traditional explanation
of how steam distillation works, it should distill in a concentration of 2%. I think it's easy to conclude that the traditional steam distillation
model doesn't explain everything, but that discrepancy seems to be glossed over by modern chemistry.
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Magpie
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Thanks UC235. This was only a proof-of-concept demonstration. I have gotten good yields with cloves.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Panache
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| Quote: Originally posted by JJay | | I don't completely understand how steam distillation works, but I think it might have something to do with hydrogen bonding. Obviously heavier
silicone oils would be less volatile than lighter ones ceteris paribus. |
It a physical chemical phenomena and only works for substrates typically between, 0.5-3% soluble in boiling water, any lower or higher and the
distillation rates tend toward zero very quickly.
You have some flexibility if you can vary the steam pressure. These distillations work infinitely more efficiently if you lead a steam source into
your flask, preferably of higher pressure/temoerature that what you could achieve at 1atm (i.e. 100C).
The best explanation of the theory is in Aitken Physical Chemistry, a bible of undergrad physical chemistry, I recommend anyone with an interest in
chemistry to purchase a copy. in twenty years of chemistry I still constantly refer to it.
As far as the foaming goes, trial and error, will often land you a defoaming agent that is effective for your system, but it can be infuriating. A
rock solid method that never fails is a whip stirrer (basically a thin piece of filament, that is mechanical driven from overhead at high speeds well
above the fluid level in the flask. it simply destroys any foam. As it encounters no resistance it need not be driven with a high torque motor, just a
fast one.
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JJay
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I just took a look at Atkins' Physical Chemistry's explanation of how steam distillation works (I never took p-chem, but the book looks familiar), and it gives the
traditional partial pressures explanation, although unlike many sources, it presents it as an estimate. I suppose if I read the entire chapter on
distillation it might contain enough information to work out accurate steam distillation proportions from other physical properties... but if I
directly apply its steam distillation equation, I already know it will lead to an estimate at best and in the case of benzyl alcohol, a wildly
inaccurate one.
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happyfooddance
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No one has mentioned it, so I'll ask; are you guys using boiling chips?
I am assuming that you are all doing an internal steam distillation, not an external. I have done this procedure many times, internal and external,
and I know that in the past I have experienced what you guys are talking about (frothing, insane bumping, to the point of product exiting via take-off
adapter!) Even when I do external S.D., I put porous plate in the flask w/ the material (also in the steam generator), but it is especially important
when performing an internal steam distillation.
| Quote: Originally posted by Magpie | I have just set up to steam distill 9g of cinnamon bark in a 500 ml rbf with Claisen adaptor. 150 ml of water was added to the pot. I'll report back
on any foaming. The bark was ground for 30s to a coarse powder.
[Edited on 18-9-2017 by Magpie] |
That seems like too little cinnamon to be efficient, and probably not enough water. Was the rbf half full? It might seem counter-intuitive, but having
less-than-half-full rbf's seems to exacerbate bumping in many situations. I am guessing due to an increased tendency to superheat. Trying to avoid
bumping by reducing headspace is walking a fine line, in other words. Just my opinion, but again: I distill cinnamon all the time with no problem 
Also, what do you guys use your extract for? The distillate when done properly has nice shining globules that sink to the bottom, coalesce rather
easily (0-5°C seems optimal to me), these will need to be re-distilled at reduced pressure, preferably, to obtain pure cinnamaldehyde. I transfer the
aqueous layer to a spray bottle, and add a little of the concentrate, to make a very effective insect repellant. If it is at the proper concentration,
it will immobilize flies, and kill many insects. Give it a shake before using. Best smelling fly swatter ever.
The rest I use for culinary endeavors.
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