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Author: Subject: Separation of toluene and isobutanol
DrScrabs
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[*] posted on 8-8-2019 at 11:09
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!

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[*] posted on 8-8-2019 at 11:29


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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[*] posted on 8-8-2019 at 15:36


Would isobutanol complex with calcium chloride?



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[*] posted on 8-8-2019 at 16:47


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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[*] posted on 8-8-2019 at 17:09


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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[*] posted on 8-8-2019 at 17:34


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.


It wouldn't give you the ether?




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[*] posted on 8-8-2019 at 19:08


Quote: Originally posted by SWIM  
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.


It wouldn't give you the ether?

That, I think, will depend on temperature. I believe higher temperatures favour elimination to give the alkene, and lower ones the ether.




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[*] posted on 8-8-2019 at 19:15


How much of this mixture are you buying a lot of a little?
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[*] posted on 8-8-2019 at 19:34


Quote: Originally posted by SWIM  
Would isobutanol complex with calcium chloride?


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.




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[*] posted on 8-8-2019 at 20:05


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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[*] posted on 8-8-2019 at 22:52


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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[*] posted on 9-8-2019 at 14:54


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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[*] posted on 10-8-2019 at 00:03


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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[*] posted on 10-8-2019 at 15:06


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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[*] posted on 10-8-2019 at 21:38


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.



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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[*] posted on 11-8-2019 at 02:09


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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[*] posted on 14-8-2019 at 12:11


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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[*] posted on 16-8-2019 at 07:30


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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[*] posted on 17-8-2019 at 05:58


Yeah man deleted my complete post accidentally.

In short: I try washing a half liter first.
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[*] posted on 29-8-2019 at 10:00


Quote: Originally posted by Tsjerk  
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]


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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