Warning: In this video we boil highly flammable liquids. Fire safety protocols must be in place.
Greetings fellow nerds.
I need some toluene for my lab and in the past I was able to buy it directly as paint thinner.
But now I canít find a pure source
and all i could get was this lacquer thinner that claims to contain toluene mixed with methanol and methyl ethyl ketone.
Since i have no other choice iím going to try and fractionally distill off the toluene.
Now before we begin we have to figure out if itís even worth doing.
If the toluene composition is very low, then it might be more worthwhile to search for other sources.
The quickest way to find out is to search for the material safety data sheet from the manufacturer.
These sheets usually state a range of compositions for chemical products.
Now manufacturers tend to keep their proprietary formulations a secret,
and wonít state the exact composition, but the range is usually helpful.
Looking at this company and typing in the product number we find something interesting,
the MSDS says the product also has acetone.
But the label says it just contains toluene, methanol, and methyl ethyl ketone.
The product number and even the pictures on the website match, so why the difference?
Perhaps i got an old container from the store or the manufacturer didnít label it correctly, mistakes can happen.
Alternatively, maybe the manufacturer has different formulations for different countries based on the local cost of materials
and i got a different formula for a different MSDS.
Nonetheless the toluene content is pretty good, almost half.
But for greater confidence, we can do some crude testing.
Here iím mixing 50mL of the lacquer thinner with 50mL of water.
Methanol, methyl ethyl ketone and acetone if it is present,
are all very soluble in water, but toluene is almost insoluble.
Therefore, by mixing the lacquer thinner with water I should see a floating layer of non-polar solvent
consisting mostly of toluene and some of the other components partitioned into it.
Looks like we have something, about 32 mL worth out of 50 mL.
Now while the volume is a misleading because some of the methanol and ketones are also dissolved in it,
this still seems worthwhile to try and distill.
So here is our fractional distillation setup.
If you want to know how the whole thing is assembled and used you can refer to my previous video on the topic.
Iíve included links in the video description.
Okay, letís turn on the stirring, the heating and the cooling water.
Now when doing a distillation it helps to thoroughly research your components
and the azeotropes and list them out in a table in order of temperature.
We can see that acetone and the acetone methanol azeotrope boil at around 56 to 55 degrees Celsius,
while the next cluster of compounds boil around 64 degrees Celsius.
So if weíre condensing near 55 degrees then we know we have acetone and its azeotropes.
But if we go past that into the 64 degree range before we condense then we know we have no acetone.
And it looks like that is the case, weíre entering the 60 degree range and still nothing has condensed.
And it seems weíre condensing at around 62 degrees.
The difference between experiment and theory is likely due to my thermometer being a cheap ebay acquisition
and the fact that itís thermocouple based which inherently
tends to have a couple of degrees of error without stringent calibration.
A lesser contribution to the error is the fact that the barometric pressure in my lab is unknown.
Looks like weíre getting a nice fraction of methanol azeotropes.
Unfortunately since the boiling points are so close together,
iíll be unable to tell when one fraction is finished and the other begins due to the poor resolution of my thermometer.
Another issue is that my fractionation column might not be good enough to resolve a 0.6 degree difference in components.
Professional distillation setups have very precise and accurate thermometers
and extremely efficient columns that can resolve the difference.
Anyway, iím not too worried. Iím only interested in getting pure toluene and not the methanol azeotropes.
While i can separate the components further just using my amatuer equipment by using additional techniques,
itís not worth my time.
I wonít discard it though, the azeotropes are still 88% methanol
and thus useful as as an impure source of methanol
if the other components are not reactive toward my chemistry.
Okay looks like the temperature is rising again and weíre going past the methanol azeotropes.
At this point we might be condensing methyl ethyl ketone.
Iím going to change out the receiver and collect this new fraction.
For those wondering, iím so hellbent on getting toluene because itís one of the base chemicals for making pyrimethamine.
Hmm, looks like weíre moving past the boiling point of methyl ethyl ketone
which should be around 79 degrees celsius.
Perhaps iím heating too much and overloading the column with vapor.
Iím going to turn down the heat just a bit to slow down the distillation.
Well that sucks, now itís going too slow and not reaching the top of the column at all.
And yet i only dialed back the heat a small amount.
This can happen with distillations where the column loses too much heat
and completely condenses out before the vapors can exit at the top.
But sometimes the properties of the component are such that itís very easy to overload the column and not get good separation.
Now if i played with the heating i might find that spot in between no condensation
and overloading where i get good separation.
But because the best heating spot keeps moving as the composition of the source flask keeps changing iím not going to bother.
Instead Iím going to turn up the heat and just boil out this low boiling component even if i loose a bit of toluene.
I can always readjust my column and improve performance later.
I just want the toluene and there should still be a lot left over.
And there we go, iím definitely overloading the column now and getting very crappy separation.
But at least iím pushing out all that methyl ethyl ketone along with some toluene.
If we were getting good separation then the temperature at the top of the column would tend to stick to one temperature
as that pure component or azeotrope distilled off.
But if weíre getting bad separation then the temperature would continuously vary as it is here.
Okay, looks like we finally reached the boiling point of toluene and have boiled out all of the lower boiling components.
The temperature seems stable so this toluene should be pure.
Let me change out the receiver. And now weíre collecting pure toluene.
Now you might wondering if mixing with water allowed me to separate most of the toluene directly,
then shouldnít I have done that first and skimmed off the impure toluene layer
so I could distill far less liquid and make my overall job much easier and faster?
Youíre absolutely right and that is a very viable approach.
I personally didnít do that because i wanted to recover the methanol azeotropes
and methyl ethyl ketone for other experiments.
The solution of water mixed with methanol and methyl ethyl ketone is less useful to me.
Disposing of it is a hassle and distilling it would have defeated the purpose of saving time.
Although looking back at how badly the methyl ethyl ketone and toluene overlapped
Iím starting to think water mixing might have been viable.
Oh well. At least i have pure toluene now.
And we are done.
The source flask just has some impurities so weíre going to turn off the heat and let it all cool.
And here is our collection of fractions.
Fraction 1 is what i believe is the azeotropes of methanol.
Fraction 2 is the mixture of methyl ethyl ketone and toluene that came from the overloaded column.
And fraction 3 is our pure toluene.
There is about 250 mL of toluene in there which is about what i need.
So I can stop here.
But of course, you guys donít pay me to cut corners.
So letís see if there are any simple ways we can some better separation of fraction 2.
Now there are a few ways we can approach this.
One, we can mix it with water and try and extract it out.
And to be honest this is probably the best way.
Two, we can buy an even longer column to get more separation power and thus possibly separate the components.
But as you can see I donít think i can fit a longer column in my existing setup.
And the third way is to improve my existing setup by insulating the column.
And here we are with just fraction 2 being distilled and the column has been wrapped in aluminum foil.
Since lowering the heating resulted in the vapors condensing out before they reached the top of the column,
by insulating the column theyíll retain heat better.
The drawback of this approach is that the column is easier to overload so you have to go even slower.
But since we want to go slow anyway to get better separation, this shouldnít be a problem.
And there we go. Odd, our condensation temperature seems to be sticking at around 82 celsius.
While we are getting good separation since itís not continuously rising, 82 does not correspond to methyl ethyl ketone.
Perhaps there are other ingredients in the lacquer thinner or other azeotropes iím not aware of.
Maybe iím still overloading the column but only very slightly.
Oh well iíll keep going, maybe i can still get some good toluene separation.
So once again the heating is insufficient to vaporize this particular composition of components to reach the top of the column.
Either that or weíre transitioning to toluene now.
Iím going to change out the receiver and slightly increase the heat.
And there we go. As you can see, distillation can be quite a time consuming headache.
Especially if the particular mixtures youíre working with exceed the capabilities of your equipment.
I was able to easily distill hydrobromic acid and the methanol azeotropes.
But this methyl ethyl ketone and toluene mixture is giving me trouble.
Something about that mixture requires more separation power than my column has.
Looks like weíve reached the temperature for toluene.
So let me change the receiver again.
A very powerful professional column is something called a spinning sideband distillation column
which uses an actively spinning central element to slam down condensation into the source flask.
Only the volatile vapor can pass.
The spinning element makes it extremely difficult to flood or overload so it can use a vacuum insulated column without problems.
Such a column is very expensive so iíll probably never get one.
But who knows, maybe iíll build one if i can assemble the right parts.
And we are done.
Despite not getting good separation of the methyl ethyl ketone
the insulated column still let us improve separation of toluene from fraction 2.
And here are our fractions.
2a is the stuff that came off at 82 degrees whatever that is.
Fraction 2b is the overlap of 2a and toluene, which is very little.
And 2c is our extra toluene.
The insulated column did help.
And here is all of our fractions.
As i said before fraction 1 is the azeotropes of methanol
and will go on to be used as an impure methanol source when that is acceptable.
Iím not sure what to do with fractions 2a and 2b.
There is not enough to try further fractionation so iíll probably just save it.
And fractions 2c and 3 is toluene which will go on to making pyrimethamine.
And that is how you use fractional distillation to separate the useful components of lacquer thinner.
Thanks for watching.
If you would like to support the continued production of science videos like this one. Please support the channel on Patreon. Links are in the video description.