jwarr
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distillation - vacuum questions
I'd like to attempt a simple fractional distillation of a natural oil blend using a simple Liebig condensers setup. My question is two parts. First,
since these are high boiling point oils (above 200 degrees Celsius) I'm hoping someone can suggest how powerful the vacuum pump should be to make sure
I'm not losing oil to degradation. Second, given the vapor pressure for the fraction I'm looking to keep and the amount of vacuum applied, how can I
determine the temperature at which the fraction will come over? If this is a basic question and you're inclined to give me a "read a chemistry book"
as an answer please instead kindly point me in the direction of any reference that may be useful.
Thank you for your help guys.
[Edited on 19-7-2009 by jwarr]
[Edited on 20-7-2009 by jwarr]
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Klute
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You need to use a nomograph: a curve will give you the bp of your compound at a given pressure. A vacuum attainable by a aspirator station, ei 25mmHg
should be sufficient, more is better.
I think there is a simple nomograph somewhere on the net.. ANyone got a link?
\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
-Alice Parr
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crazyboy
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What kind of oil are you distilling? Usually when someone says "distillation of an essential oil" it means sassafras oil to safrole...
Anyway this is probably what you want http://www.erowid.org/archive/rhodium/chemistry/equipment/no...
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turd
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Actually the exact temperature and the strength of the vacuum are not really that important, since you will typically just use the largest fraction.
As long as the vacuum isn't too weak, of course. Aim for the 10 mbar region, then you should be OK. For an idea where your fractions will distill,
check the literature and extrapolate.
But what you really want is a stable vacuum source (otherwise how are you going to cut your fractions?) that doesn't collapse under
the slightest hole in your setup and that has a decent end vacuum. That's why I strongly recommend to shop at your favourite internet auction house
for new(!) rotary wane oil pumps for ~$100-200, which often go down to <10 mbar. If that pump is only used for distillations of high boiling
liquids (and not for the removal of solvents and vacuum filtration) it will last a long time.
Good luck & nice essences. 
PS: Since essential oils are often complex mixtures, a small column wouldn't hurt!
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chemrox
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Quote: Originally posted by crazyboy  | What kind of oil are you distilling? Usually when someone says "distillation of an essential oil" it means sassafras oil to safrole...
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This kind of counter-post is the kind of thing that keeps the cooking vs chemistry friction alive around here. You have no reason to make this
assumption. The world of essential oils is vast and fascinating. I make perfumes as a hobby. For crazyboy I'd make one that is 100% n-butyl
mercapton but would anyone notice?
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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crazyboy
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I don't consider that a "counter post". Knowing which oil he was distilling is useful for determining how much vacuum, is required. Since distillation
of sassafras oil to safrole is more common than most other essential oil distillations I figured that was it.
For the record I have no problem with people distilling safrole or asking questions on how to synthesize precursors.
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woelen
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Yes, I agree with chemrox. We should stop insinuating each newcomer is a cook when he/she asks this kind of questions. This question is so general
that no a-priori conclusions should be drawn on cookery.
Of course, when more details are supplied, then more detailed and more helpful answers can be given.
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jwarr
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Not that it's of any importance, but I'm attempting to distill Thymol from a carrier oil. Anyway, I've found a vacuum pump that is rated at an
ultimate vacuum of 75 micron (75 millitorr). I'd like to get some input from people using vacuum rated at about this level. Can I realistically
expect to pull this sort of pressure from a distillation setup? That seems like a mighty powerful vacuum. My oil would come over at less than room
temperature and that doesn't seem like it would make sense.
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