Sciencemadness Discussion Board - Need help at distilling Toluene

Need help at distilling Toluene

AndrewOfWallachia - 4-7-2025 at 04:01

I need toluene. Buying it is out of the question because shit country.
I am trying to distill it from paint thinner. I have found only one type of paint thinner sold here which contains it "D209" type thinner. I checked its MSDS and it mentioned it contains between 2.5-10% acetone, 10-25% 1-butanol, 25-50% (n-)butyl acetate, and 25-50% toluene.

[What I am about to describe are my 2 attempts both of which were carried out in the same manner and had the same results]
I first washed the thinner with water in order to remove the acetone and butanol, now I should be left with a mixture of butyl acetate and toluene.
I set up a fractional distillation for it with a 300mm Vigreux column and Liebig condenser, the solvent mixture was in a small boiling flask with a few brick chips as boiling chips that was in an oil bath (sunflower seed oil) heated by an ancient hot plate (no variable resistor or PWM gizmo i.e. it's either ON or OFF, can't regulate heating rate). --HERE'S THE WEIRD PART-- The mixture started boiling and the thermometer in the stillhead jumped to around 86-90 degrees and distillate started condensing [I originally assumed this to be some azeotrope that trace amounts of acetone or butanol might have formed], after which, the temperature started slowly and steadily rising until about 104 degrees, where it stayed constant! Now the thermometer I have is graded once every 2 degrees and obviously it also has a margin of error, but that's a whole 6 degrees lower than the 110 boiling point of toluene. I let it distill to see what would happen and by the end, basically the whole mixture had been relocated into the receiving flask without ever exceeding the 104 degree mark- let alone the 126 degrees that butyl acetate needs to boil. I stopped since everything was distilled and now I am profoundly confused?!?

So I am asking here. Do you guys have any idea what the hell is happening here? How can I reliably obtain my toluene? Thanks a lot in advance!

PS: Now on top this I have a bunch of mystery distillate and washing water as waste, what's the best way to safely dispose of it? Considering it contains toluene (supposedly), I was thinking of pouring it onto a plate and just burning it off. Again, thanks!

[Edited on 4-7-2025 by AndrewOfWallachia]

BromicAcid - 4-7-2025 at 05:20

Out of curiosity, what do your recoveries look like after washing and how much water are you using? Toluene and butyl acetate are only slightly soluble in water but when you start dissolving a lot of acetone/butanol I would wonder how that is going to affect the solubility. At a glance I would expect issues with emulsions, no problems with that?

Ignoring the boiling point you're seeing, a Vigreux doesn't offer the best separation in the world, and in order to have a real fractionation you need a fractional takeoff head providing continuous and controllable return to a column. Not saying the distillation in worthless, just that it needs another pass. You might also want to wash with brine or dry over something before starting the distillation just to remove trace water which might be impacting things.

Poking around for azeotrope data I see you've already done the same. I also see you were asking about separation. I know someone said a Vigreux would be good enough but I really think you need a few passes. Very curious if things will clear up with another distillation assuming you have a forecut and pot heel you're chucking along the way. Remember, a fractional distillation is meant to simulate multiple simple (short path) distillations. This is probably not bad material, and might be your first step to your target.

Another potentially bigger issue is that you confirm you have your thermometer in the correct location during the distillation. I learned the hard way early on that just a few mm in each direction can really impact the number you're seeing. How fast was your distillation, did you just rip it over (considering you have no control over the hot plate) or did you baby it along by turning the hot plate on and off? If you're not very aggressive that can cause lower Bp because the thermometer is not bathed in the vapors. Too fast and you get no separation.

I wouldn't boil it off on your hotplate just because of the potential for issues (sparks, ignition). But when it was created it was meant to just evaporate, put it in a large container, leave it outside, don't let it rain on it and it should be gone in short order.

Of course the SDS might just be wrong, it happens and it's a pain.

I remember when I started doing chemistry 25 years or so ago I was asking a million questions, but now after running distillations for as long as I have it's a lot easier to keep all the plates spinning at the same time.

AndrewOfWallachia - 4-7-2025 at 05:47

Quote: Originally posted by BromicAcid

Out of curiosity, what do your recoveries look like after washing and how much water are you using? Toluene and butyl acetate are only slightly soluble in water but when you start dissolving a lot of acetone/butanol I would wonder how that is going to affect the solubility. At a glance I would expect issues with emulsions, no problems with that?

Ignoring the boiling point you're seeing, a Vigreux doesn't offer the best separation in the world, and in order to have a real fractionation you need a fractional takeoff head providing continuous and controllable return to a column. Not saying the distillation in worthless, just that it needs another pass. You might also want to wash with brine or dry over something before starting the distillation just to remove trace water which might be impacting things.

Poking around for azeotrope data I see you've already done the same. I also see you were asking about separation. I know someone said a Vigreux would be good enough but I really think you need a few passes. Very curious if things will clear up with another distillation assuming you have a forecut and pot heel you're chucking along the way. Remember, a fractional distillation is meant to simulate multiple simple (short path) distillations. This is probably not bad material, and might be your first step to your target.

Another potentially bigger issue is that you confirm you have your thermometer in the correct location during the distillation. I learned the hard way early on that just a few mm in each direction can really impact the number you're seeing. How fast was your distillation, did you just rip it over (considering you have no control over the hot plate) or did you baby it along by turning the hot plate on and off? If you're not very aggressive that can cause lower Bp because the thermometer is not bathed in the vapors. Too fast and you get no separation.

I wouldn't boil it off on your hotplate just because of the potential for issues (sparks, ignition). But when it was created it was meant to just evaporate, put it in a large container, leave it outside, don't let it rain on it and it should be gone in short order.

Of course the SDS might just be wrong, it happens and it's a pain.

I remember when I started doing chemistry 25 years or so ago I was asking a million questions, but now after running distillations for as long as I have it's a lot easier to keep all the plates spinning at the same time.

OK! Good! That means you won't mind me asking as many question as you (probably more)

Let me start off with saying that I can't really get any more advanced with equipment past a Vigreux column (hell, I don't even have lab jack!), this stuff is just not easily available here (again, dog-piss country) plus I don't really want to buy it either. So, I'll have to make the Vigreux work.

My thermometer's bulb was basically in-line with the opening leading to the condenser in the stillhead, its tip was just a little bit under the height of the opening, sure, the thermometer isn't great, maybe it's shitty enough to show 104 instead 110 degrees, but almost all of the liquid evaporated and never did it get close to the 126 degrees that would be needed for that. So it can't be just thermometer error, furthermore, I did to quote you, kind of "Rip through" the distillation, I had my hotplate powered off for a very brief moment once vapor started entering the stillhead but it was running most of the time. If doing this would have lead to getting poor separation I would have had too see the highest boiling point going through too, no? That's what's confusing.

Another thing, I don't really understand what you mean by another distillation assuming I have a forecut and pot heel I'm chucking along.

I mean, I'm starting to suspect that I've just been blatantly lied to by the MSDS, but how WRONG can it be now?? Wrong enough to include a whole 25-50% chemical that isn't actually there? What is your experience/how plausible is it that the MSDS is just being stupid?

Thank you for the reply by the way.

[Edited on 4-7-2025 by AndrewOfWallachia]

[Edited on 4-7-2025 by AndrewOfWallachia]

BromicAcid - 4-7-2025 at 07:15

So if you're fractionating something usually you have a forecut, the first bit that comes over. The size is usually determined by those lower temps you were seeing on your head temperature. You would collect that lower bit in its own flask to discard. Then you would swap the receiver and collect a main fraction which would be mostly product, and when the head temp drops or goes up you would stop the distillation, and usually there would be something left in your flask, these would be your pot heels. So really you're removing light boilers in your forecut and leaving behind high boilers in your pot at the end. If you're just bringing everything over and collecting it in the same flask then you're not separating anything.

Since I wasn't there I'm just trying to make this as clear as possible, you may or may not have done all of this.

If you want to get a good head temp it also helps to use some insulation around the glass on the outside of the distillation head. My money is on some issue with the location of the thermometer bulb. There are also different types of thermometers, some immersion style thermometers need to be quite a bit into the liquid to give a good reading. There's just a lot that can go wrong at that point. If you want to just get a photo of the temp probe in place in the still head that would shut me up on the subject. But - as you're saying, if the thermometer is in place, and your mixture is what you think it is, and you're heating it to get a good head temp then the head temp should be at the boiling point of toluene or higher due to the butyl acetate.

If you really wanted to get into it maybe you could try an acid catalyzed hydrolysis of your mix to try to remove the ester chemically. But that seems like a pain in the rear.

The MSDS is usually somewhat correct. When they create them they make these wide ranges not because they have no control over their process but for other reasons. Like the price of a solvent being seasonal or because one of their starting materials is actually a waste stream from a different process and varies in composition. I mean, I would think there is toluene in there and I would be surprised if there was not, but I wouldn't say it's impossible.

AndrewOfWallachia - 4-7-2025 at 07:30

Quote: Originally posted by BromicAcid

So if you're fractionating something usually you have a forecut, the first bit that comes over. The size is usually determined by those lower temps you were seeing on your head temperature. You would collect that lower bit in its own flask to discard. Then you would swap the receiver and collect a main fraction which would be mostly product, and when the head temp drops or goes up you would stop the distillation, and usually there would be something left in your flask, these would be your pot heels. So really you're removing light boilers in your forecut and leaving behind high boilers in your pot at the end. If you're just bringing everything over and collecting it in the same flask then you're not separating anything.

Since I wasn't there I'm just trying to make this as clear as possible, you may or may not have done all of this.

If you want to get a good head temp it also helps to use some insulation around the glass on the outside of the distillation head. My money is on some issue with the location of the thermometer bulb. There are also different types of thermometers, some immersion style thermometers need to be quite a bit into the liquid to give a good reading. There's just a lot that can go wrong at that point. If you want to just get a photo of the temp probe in place in the still head that would shut me up on the subject. But - as you're saying, if the thermometer is in place, and your mixture is what you think it is, and you're heating it to get a good head temp then the head temp should be at the boiling point of toluene or higher due to the butyl acetate.

If you really wanted to get into it maybe you could try an acid catalyzed hydrolysis of your mix to try to remove the ester chemically. But that seems like a pain in the rear.

The MSDS is usually somewhat correct. When they create them they make these wide ranges not because they have no control over their process but for other reasons. Like the price of a solvent being seasonal or because one of their starting materials is actually a waste stream from a different process and varies in composition. I mean, I would think there is toluene in there and I would be surprised if there was not, but I wouldn't say it's impossible.

Alright. Yeah, obviously I know what you're talking about in the first part, I was just not at all familiar with the terms you used. While it is true that on my second try (the one I did today) I didn't switch out the receiving flask, that's because I was waiting to reach the 110 degrees (or in the neighborhood) that I needed to be sure it's toluene, except, as you know, the temperature was never reached by the point that the mixture had completely boiled into the other flask.

Also, what you're telling me about the wide margins in the MSDS, is actually interesting! I always thought that the reason for the enormous margin of error was that they didn't want to give away the exact formulation so that other brands don't just copy it.

[Edited on 4-7-2025 by AndrewOfWallachia]

Lionel Spanner - 4-7-2025 at 12:07

Quote: Originally posted by AndrewOfWallachia

Also, what you're telling me about the wide margins in the MSDS, is actually interesting! I always thought that the reason for the enormous margin of error was that they didn't want to give away the exact formulation so that other brands don't just copy it.

According to the Classification, Labelling and Packaging Regulation, distributors are only legally required to declare ranges on the MSDS, and only for hazardous materials. Non-hazardous materials generally aren't listed at all.

Radiums Lab - 4-7-2025 at 13:16

Maybe the altitude is causing the small variation. Did you check the Rault's graph of azeotrope.

AndrewOfWallachia - 5-7-2025 at 00:28

Quote: Originally posted by Sulaiman

When I used my 300mm Vigreaux column I got about ONE theoretical plate performance increase over a simple distillation.
If you go VERY slowly with constant heating power and no draughts then maybe TWO plates.

If your heating is not constant you will get very poor fractionation.
(I recommend an 'scr dimmer' for heating control)

A 300mm Vigreaux packed with 3mm dia. glass balls adds about three theoreical plates if I go slow.
Adding a reflux condenser increases this to five or more.

Distill some water with your still setup exactly as for the toluene,
just to calibrate your thermometer,
and as above, maybe a correction for atmospheric pressure .

Fine fractional distillation is MUCH more difficult than I initially expected

[Edited on 5-7-2025 by Sulaiman]

No,no. You don't get the issue, even if my 300mm Vigreux isn't that great, that's not the BIG problem, I can just run the distillation again if I need to. The problem is that not only do I not reach the BP of toluene in the stillhead, but I never go past 104 degrees EVEN at the point of all the liquid distilling over EVEN THOUGH it contains butyl acetate that should boil at 126 degrees.

jackchem2001 - 5-7-2025 at 01:47

To make things a bit more clear, I would consider treating the mixture with alkali overnight. Then you know for sure you have just butanol and toluene rather than a mixture of many different components. You can then wash with a very large excess of water to give you toluene, which can be redistilled

[Edited on 5-7-2025 by jackchem2001]

zed - 5-7-2025 at 16:32

Ummm. Perhaps you should explore alternate supply chains. Now, me being in the USA, I can buy Toluene fairly easily at my local hardware or super-store. At least, I assume I can. Though, I might have to "sign" for it.

Alternately, it used to be available through Automotive supply stores, and professional paint stores.

Toluene can be used to "juice up" gasoline, it is rated at 120 Octane.

AndrewOfWallachia - 6-7-2025 at 01:57

Quote: Originally posted by zed

Ummm. Perhaps you should explore alternate supply chains. Now, me being in the USA, I can buy Toluene fairly easily at my local hardware or super-store. At least, I assume I can. Though, I might have to "sign" for it.

Alternately, it used to be available through Automotive supply stores, and professional paint stores.

Toluene can be used to "juice up" gasoline, it is rated at 120 Octane.

No, as I said buying it is out the question because I live in the Land of the Slaves and the home of the Cowards. Even if I could buy it though, I wouldn't because I am very new to distillation and this is the perfect starting project to actually get some some practical experience. As my end goal is to distill H2SO4, but I am not stupid enough to attempt that until I've gathered much more experience

[Edited on 6-7-2025 by AndrewOfWallachia]

AndrewOfWallachia - 6-7-2025 at 02:00

Quote: Originally posted by jackchem2001

To make things a bit more clear, I would consider treating the mixture with alkali overnight. Then you know for sure you have just butanol and toluene rather than a mixture of many different components. You can then wash with a very large excess of water to give you toluene, which can be redistilled

[Edited on 5-7-2025 by jackchem2001]

Hello! Please elaborate on the procedure you're suggesting!
It sounds very interesting. Though, I have butyl acetate and toluene, the butanol I can wash off no problem same with the acetone.

jackchem2001 - 6-7-2025 at 06:32

Starting from the stuff straight from the can, I would do something like
1) Wash a couple of times with a large amount of water (remove acetone and butanol).
2) Prepare alkali solution with NaOH. Stir with the toluene/butyl acetate overnight. Must be well stirred because it will be in two phases. Now the mixture is toluene/butanol. Any acetone that lingered through water washings will polymerise into high b.p. which you can ignore.
3) Wash many times with water to remove most of the butanol (and sodium acetate/other salts)
4) Now distill the mixture which should hopefully be mostly toluene. I would dry it first with any suitable drying salt

I did some quick searches and it looks like toluene has a higher refractive index than both butyl acetate and butanol. aybe you can use this somehow? not sure how the refractive index of a mixture behaves

[Edited on 6-7-2025 by jackchem2001]