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DrScrabs
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Separation of toluene and isobutanol
I am without my digital libary and don´t want to search the web as I want to spend the time with the familily. But I have the possibility to buy a
mixture really cheap. The isobutanol is of no interest for me, but the toluene is. Maybe somebody has an answer or a paper on the hand. Thanks!
DrScrabs
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Ubya
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the difference in bp between toluene and isobutanol is just 3°C,
and they have an azeotrope at 1atm with a bp of 101°C(57%toluene 43% isobutanol m/m), if the isobutanol is less than the toluene (much less) you can
use a good fractionating column and sacrifice the same mass of toluene as isobutanol to get rid of it as the azeotrope, and then distill pure toluene.
if the isobutanol is more than 43% of the total mass, you can't do much by normal distillation.
if you can vacuum distill the mixture at 20mmHg tge azeotrope bp is 17°C and the ratio is 90% toluene 10% isobutanol.
or you could wash it out, isobutanol has a solubility in water of 8.7ml/100ml of water, not much, and you'll need many washings to get rid if it, but
if you can manage the liters of waste it could work as toluene solubility is just 0.052g/100ml of water.
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SWIM
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Would isobutanol complex with calcium chloride?
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DraconicAcid
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If you reflux the mixture with sulphuric acid, the isobutanol will be dehydrated to an alkene, which can easily be separated from the toluene.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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j_sum1
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I was going to suggest washing with water. Toluene is poorly soluble. The alcohol should wash out ok. You won't get full separation but it won't be a
bad preliminary step.
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SWIM
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Quote: Originally posted by DraconicAcid  | | If you reflux the mixture with sulphuric acid, the isobutanol will be dehydrated to an alkene, which can easily be separated from the toluene.
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It wouldn't give you the ether?
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DraconicAcid
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That, I think, will depend on temperature. I believe higher temperatures favour elimination to give the alkene, and lower ones the ether.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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draculic acid69
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How much of this mixture are you buying a lot of a little?
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DraconicAcid
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http://www.prepchem.com/synthesis-of-butyl-ether/ says that n-butyl alcohol is soluble in saturated calcium chloride solution, so that may be a
good way to extract the alcohol.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Tsjerk
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I would buy, and think of separation later. It has to be doable in a simple manner.
I think washing with water should work, and little NaOH might work down the way.
I would start with water washings and add a little NaOH during distillation as this could break the azeothrope by de-protonating the alcohol. Not the
best reaction to run in new glassware, but a little NaOH doesn't hurt.
This proposed method could be imaginary, but there has to be a way to separate.
Edit: This stuff is 85% toluene. I don't know what the other 15% is but it is not something that forms an azeothrophe.
https://www.thr.nl/elma-thinner-tolueen-500-ml.html
[Edited on 9-8-2019 by Tsjerk]
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Metacelsus
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About the "refluxing with sulfuric acid" idea:
I'd be worried about possible side reactions with the toluene (sulfonation might be unlikely, but Friedel-Crafts alkylation by isobutyl cation
intermediates would happen under the same conditions as dehydration to the alkene).
Washing with water is probably the best plan.
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UC235
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Why are we boiling with sulfuric acid? Toluene is sulfonated under such conditions. As a protonatable species, isobutanol should be freely soluble in
room temperature concentrated sulfuric acid. Toluene is not. Just wash it repeatedly with sulfuric acid, then water. Then dry and distill.
The first wash with sulfuric will be exothermic. Keep everything chilled and go slowly.
[Edited on 9-8-2019 by UC235]
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DrScrabs
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Boiling with H2SO4 is indeed a bad idea. Washing with H2SO4 is a bit unpractical aswell as I bought 40L. I think I will go with simple H2O and CaCl2
soln. washings, followed by distillation.
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SWIM
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I was wondering if just fine grinding calcium chloride and pouring it into the solvent would, with time, scavenge the alcohol out.
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Ubya
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| Quote: Originally posted by SWIM | I was wondering if just fine grinding calcium chloride and pouring it into the solvent would, with time, scavenge the alcohol out.
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it would, but he has 40L of mixture, you would need many kilograms of calcium chloride (and then to dispose it), water washings and then eliminating
the last traces of water and alcohol with CaCl2 is a better way
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Tsjerk
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40 liters is never going to be a joy... But reading this I think the simplest method is washing with water first and than run a distillation to get
rid of the alcohol as the azeotrope. During the same time you will get rid off the water as it forms an azeotrope with toluene.
[Edited on 11-8-2019 by Tsjerk]
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DrScrabs
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I will wash with water two or three times then with CaCl2 soln, I have a 3L sep. funnel, so it´s not that annoying. A day of work maybe.
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Dr.Bob
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Both are excellent octyane enhansers, just add a few quarts to your tank at every fill up if you can buy it cheaper than gas...
For 40 L a good distillation is the first starting point, if you really want the toluene. 3 degrees is not much, but it can be used to make a decent
separation. Once you get them each mostly pure, then other methods can be used. But its a lot of work, unless they are cheap.
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DrScrabs
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Yeah man deleted my complete post accidentally.
In short: I try washing a half liter first.
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derk19
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The toluene is unfortunately replaced by other aromatics, even though only it is still called 'Toluene thinner'. If you look closely at the image on
the site it says 'Xylene' as the first ingredient.
When I went to a store in another town to get it it contained ethylbenzene instead of xylene or toluene.. Apparently even xylene was too useful?
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Mixe
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Sorry for hijacking an old thread, but I'm faced with the same issue. Not at all with these quantities though. Its just that the OTC available version
of toluene in my country is a mix of toluene, acetone and isobutanol.
So how did this pan out? Was the water-water-calcium chloride-technique effective? Any experiences or new ideas to share?
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Monoamine
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Isn't isobutanol much more water soluble than toluene? In that case couldn't you extract the isobutanol out of the toluene with water? You'll have a
small amount of water in the toluene, but you can dry it with anhydrous MgSO4 or similar, or you can do a second extraction where you
extract the wet toluene into an alkane like petroleum ether and leave the water behind.
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Mixe
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Ummm, yes, that has been said ... a couple of times in the thread above.
But on the other hand isobutanol is much more soluble in toluene than in water, so how much can you actually hope will pass over to the water phase?
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RustyShackleford
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water wash->conc CaCl2 wash -> drying with solid CaCl2->reacting the residual with sodium metal (or possibly aluminium by gallium or mercury
amalgam)
should produce a distillate with as close to no alcohol as i think is reasonable "at home".
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Tsjerk
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DrSrubs has been absent for a while. It would be nice to see him back, but I don't think that is going to happen soon.
I reread my posts, but I don't understand why I thought NaOH was a good idea. I would do what RustyShackleford says. Maybe could reflux with sulfuric
acid to get rid of the last alcohol though, but you would have to distill the toluene as it does get sulfonated, but that doesn't distill over.
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