Sciencemadness Discussion Board

Separation of toluene and isobutanol

DrScrabs - 8-8-2019 at 11:09

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

Ubya - 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.

SWIM - 8-8-2019 at 15:36

Would isobutanol complex with calcium chloride?

DraconicAcid - 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.

j_sum1 - 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.

SWIM - 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?

DraconicAcid - 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.

draculic acid69 - 8-8-2019 at 19:15

How much of this mixture are you buying a lot of a little?

DraconicAcid - 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.

Tsjerk - 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]

Metacelsus - 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.

UC235 - 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]

DrScrabs - 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.

SWIM - 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.

Ubya - 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

Tsjerk - 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]

DrScrabs - 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.

Dr.Bob - 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.

DrScrabs - 17-8-2019 at 05:58

Yeah man deleted my complete post accidentally.

In short: I try washing a half liter first.

derk19 - 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?

Mixe - 28-11-2021 at 18:34

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?

Monoamine - 28-11-2021 at 21:41

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.

Mixe - 29-11-2021 at 01:07

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?

RustyShackleford - 29-11-2021 at 05:14

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".

Tsjerk - 29-11-2021 at 08:36

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.

Mixe - 29-11-2021 at 11:27

But I'm a bit confused about the sulphuric acid. I've read up ferociously but the information points everywhere: protonated and dehydrated alcohol = ester = even more soluble in toluene = even more problems, but then there's the question of temperature, and if the end product is isobutylene, etc etc ...

As for the solubility in water, would increased temperature favor the washout of isobutanol from toluene to water? If I boil a mixture of water and the mixed solvent?

DraconicAcid - 30-11-2021 at 11:42

The acid reacts with the alcohol to give isobutylene, which will evaporate and be lost during the distillation.

S.C. Wack - 1-12-2021 at 14:46

Quote: Originally posted by Mixe  
But I'm a bit confused about the sulphuric acid. I've read up ferociously but the information points everywhere: protonated and dehydrated alcohol = ester = even more soluble in toluene = even more problems, but then there's the question of temperature, and if the end product is isobutylene, etc etc ...


It would be easy enough to test with a test tube and less than a minute of shaking...basifying the aqueous layer either releases the alcohol or doesn't (I'd heat to boiling w/NaOH and see what the vapor smells like, after washing w/bisulfite in the first place)...isobutylsulfuric acid would be the product, and I suspect that it's more soluble in the acid.(ethylsulfuric acid is insoluble in ether for instance) (if CaCl2 reacts with the alcohol other than salting it out of aq. solution, it does so in the anhydrous form)

Perhaps some cheap substance can be found which preferentially absorbs a large amount of the more polar cpds...no doubt y'all will get testing and report back...my entry for the grand prize: oxidizer, NaOH, bisulfite.

[Edited on 2-12-2021 by S.C. Wack]

Mixe - 2-12-2021 at 02:43

Yes, I will get right into this and report back. I just have to produce some conc H2SO4 first... In my country, its a listed chemical, and the level of control is unbelievable. At this time, for me, the only available source is finding older car batteries and doing the kind of messy work-up from there.

Tsjerk - 2-12-2021 at 12:03

I wouldn't use sulfuric acid from the start, just go for water and CaCl2, maybe you can reflux with sulfuric acid when CaCl2 doesn't work.

S.C. Wack - 4-12-2021 at 08:50

It's entirely possible that the alcohol is just as soluble in other mineral acids. Either way, and also before treatment with dry CaCl2 for a length of time, the acetone has to be removed first.

Heating with sulfuric acid would sulfonate toluene and condense acetone long before dehydrating the alcohol; that operation is performed at 160-200C.

DocX - 25-12-2021 at 10:46

Quote: Originally posted by S.C. Wack  
It's entirely possible that the alcohol is just as soluble in other mineral acids. Either way, and also before treatment with dry CaCl2 for a length of time, the acetone has to be removed first.

Heating with sulfuric acid would sulfonate toluene and condense acetone long before dehydrating the alcohol; that operation is performed at 160-200C.


Ok, so what is your practical advice in this case? Of course the aceton is distilled off first, thats easy. Yes, adding sulphuric acid would sulfonate the toluene, I can see that, but that brings us full circle around to the beginning: how to separate isobutanol and toluene? Or if the isobutanol is unchanged by adding sulphuric acid but the toluene is sulfonated, would that be a step closer to separation?

Could one, for example, add sulphoric acid to the mix of isobutanol and toluene, crystallize the toluenesulphonic acid, filter the crystals out, then boil them in water and distill off the hydralized pure toluene?




[Edited on 20212121/12/25 by DocX]

Tsjerk - 25-12-2021 at 13:20

Even if you could hydrolyse the pTsOH efficiently, you would need about a gram of sulfuric acid for every gram of toluene.

I would still first try to extract the alcohol with water and remove the last bit with CaCl2. You can salt the isobutanol from the water with CaCl2 as well.

[Edited on 25-12-2021 by Tsjerk]

DocX - 26-12-2021 at 09:27

Quote: Originally posted by Tsjerk  
Even if you could hydrolyse the pTsOH efficiently, you would need about a gram of sulfuric acid for every gram of toluene.

I would still first try to extract the alcohol with water and remove the last bit with CaCl2. You can salt the isobutanol from the water with CaCl2 as well.

[Edited on 25-12-2021 by Tsjerk]


Yes yes, that is suggested a kazillion times in this thread, and naturally that will be steps 1-4, and fairly obviously so. But if you really really want clean toluene, I'm wondering about that last, definitive step.

Tsjerk - 26-12-2021 at 13:52

I understood you wrong because you suggested adding sulfuric acid to the mix, not to the purified toluene.

DraconicAcid - 26-12-2021 at 20:01

If you want the last definitive step for removing all isobutanol from toluene, reflux it over sodium metal before distilling.

Triflic Acid - 27-12-2021 at 08:36

A cheap, albeit not greatly effective method, would be to get the reflux a large amount of this mixture with a large amount of anhydrous copper sulfate. This would dehydrate the isobutanol to isobutene, which should escape the solution as the toluene refluxes. https://pubs.acs.org/doi/10.1021/jo01293a030 This won't get rid of it all, but since copper sulfate is so cheap, you can buy it by the kilo for a few bucks, it could be a good starting point in removing the isobutanol, then do some of the more expensive methods listed above

DocX - 27-12-2021 at 13:06

Quote: Originally posted by DraconicAcid  
If you want the last definitive step for removing all isobutanol from toluene, reflux it over sodium metal before distilling.


Now this is interesting! For a n00b like me, what reaction does this provoke?

DraconicAcid - 27-12-2021 at 13:46

Quote: Originally posted by DocX  
Quote: Originally posted by DraconicAcid  
If you want the last definitive step for removing all isobutanol from toluene, reflux it over sodium metal before distilling.


Now this is interesting! For a n00b like me, what reaction does this provoke?


The alcohol will be converted to sodium alkoxide, which is non-volatile. Also very good for removing the last traces of water and oxygen.

DocX - 27-12-2021 at 14:49

Quote: Originally posted by DraconicAcid  
Quote: Originally posted by DocX  
Quote: Originally posted by DraconicAcid  
If you want the last definitive step for removing all isobutanol from toluene, reflux it over sodium metal before distilling.


Now this is interesting! For a n00b like me, what reaction does this provoke?


The alcohol will be converted to sodium alkoxide, which is non-volatile. Also very good for removing the last traces of water and oxygen.


Yes, I was able to conclude that by UsingThe Damn Search Engine. Sorry for blurting out questions and thank you for your patient reply. What I haven't been able to really understand from my search results is if the sodium will react in any way with the toluene, and if the reaction with the 5-10% of isobutanol will be violent and risky?

DraconicAcid - 27-12-2021 at 15:31

Sodium will not react with toluene or other hydrocarbons (apart from alkynes, possibly)- when I as a grad student, most of our solvents (benzene, toluene, ethers, alkanes) were purified by refluxing over sodium (with a bit of benzophenone) under nitrogen for an hour or two before distillation. The benzophenone was there as an indicator- if it formed the blue radical anion with sodium, you knew it was very dry.

I don't think the reaction with 5-10% isobutanol would be very violent, but I'd dry it with something else first, just be be safe.

DocX - 30-12-2021 at 00:16

This was perfect! Thank you so much. If I pull that off, I have a relatively cheap and readily accessible true OTC source of toluene.

Jome - 8-5-2022 at 04:13

I have the same problem as Mixe, toluene is only available as a toluene-acetone-isobutanol mix in the ratio 70-80/15-20/5-10% respectively.

Acetone is completely miscible with water so that'll be easy, just a sep funnel and some water washings. Any remaining acetone (bp=56 C) will be gone long before anything else starts distilling over. I looked up the boiling points (in C of course) of any possible azeotropes as well as the pure substances:

110.6 Toluene
108.4 Isobutanol
101.2 Toluene/Isobutanol azeotrope 55.5% toluene
100.0 Water
89.7 Isobutanol/water heterogeneous azeotrope 30% water
85.0 Toluene/Water heterogeneous azeotrope, 20.2% water.

The obvious solution is to, as stated before in the thread, just fractionally distill off IBA/toluene followed by only toluene, sacrificing the required amount of toluene to form the 44.4/55.5 IBA/Toluene azeotrope. There is a 9.4 C difference between the azeotrope and toluene.


BUT, if a small amount of water was added instead, would said water all be consumed by forming Toluene/water vapor first, with negligible isobutanol following due to the water vapor "preferring" to form a vapor mix with toluene? The difference in BP isn't big (4.7 C), but if the water runs out....This is as you might've guessed, both a "fundamentals" and a practical question for me, but it's been gnawing at my mind lately and I don't know how to formulate in order to "just google" such a complex question.


Keras - 8-5-2022 at 05:33

Esterify the iBuOH with a high boiling carboxylic acid, e.g. benzoic acid, and use a Dean Stark to remove toluene/water azeotrope. You will get isobutyl benzoate, b.p. 241 (Practical Organic Chemistry, Mann and Saunders, p. 546), so easily separable from toluene by cranking up the heat once you don’t collect anymore water/toluene/iBuOH azeotrope

Tsjerk - 8-5-2022 at 06:52

@Jome: unless you have a very efficient column you would end up distilling a mixture of water/toluene and water/isobutanol, as the 5 degree difference is very small.

So getting clean isobutanol out of the mixture will be hard, but the different azeotropes do make it possible to end up with clean toluene.

Dr.Bob - 9-5-2022 at 11:16

I would do some test distillations first and then collect fractions for every 10% of the volume or every few degree change and just see if any are pure. It will not be trivial to separate them completely, but it should be possible to get at least a few fractions of distillate that are mostly one component, then they can be pooled and redistilled again to get nearly pure material. Then I would try to remove the last traces of alcohol or water. Trying to remove bulk water or alcohol with sodium would make a big mess or fire, most likely, but should be easy after one or two distillations. And certainly trapping the isobutyl alcohol as an ester might work, but you might add some acetyl chloride and distill off the isobutyl acetate at 118, which is above the toluene. It might be useful for something.