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Author: Subject: Can i recycle toluene solvent for a long time?
Cou
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[*] posted on 6-3-2020 at 21:12
Can i recycle toluene solvent for a long time?


toluene is kind of expensive, $22 for one quart.

i plan to use it as a fischer esterification solvent. making salicylate esters with excess of salicylic acid, for my fragrance collection. i can get xylene for $10 a quart, but toluene is more convenient for my purpose b/c of low boiling point.

I guess I can recycle the toluene over and over again. after water and bicarb washes, the remaining organic layer would be toluene and butyl salicylate. i would do simple distillation to remove the toluene (toluene BP is 110.6 C, butyl salicylate BP is 273 C), dry with drierite before reusing.


[Edited on 7-3-2020 by Cou]
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mackolol
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[*] posted on 7-3-2020 at 02:33


I think you can, especially if you`re gonna use it for the same reaction after recycling.
If you want to be sure that toluene is pure, do a fractional distillation.
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j_sum1
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[*] posted on 7-3-2020 at 03:36


Just be aware that water has some non-negligible miscibility with toluene. There is also a toluene-water azeotrope and so you may not get rid of your water through distillation.

Toluene does respond nicely to removal of water using Dean Stark apperatus. If you don't have this glassware then it is worthwhile getting something. Mine is not stricty a dean stark trap but something almost identical designed for oil extractions. It was cheap on eBay. Nurdrage has some videos showing how he cobbled together something functionally equivalent using readily available glassware.

Removing the water by this method is a surprisingly satisfying process: simple but effective. And it may be necessary for your application since you want to keep water away from your delicate esters.
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Amos
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[*] posted on 7-3-2020 at 06:29


If you have an Ace Hardware store anywhere nearby, you should be able to find a gallon for that price. Are you using heavy alcohols that aren't miscible with water? Otherwise it's generally a better idea to use the alcohol as the solvent.

[Edited on 3-7-2020 by Amos]
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morganbw
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[*] posted on 7-3-2020 at 08:02


You can recycle it forever.
Read j_sum1 / post for sure.
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Cou
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[*] posted on 7-3-2020 at 09:27


Quote: Originally posted by j_sum1  


Removing the water by this method is a surprisingly satisfying process: simple but effective. And it may be necessary for your application since you want to keep water away from your delicate esters.


The smallest Dean stark trap on Amazon is 10 mL, and I dont work on large enough scale for that. Its only worthwhile on large scale.

Otherwise, juse using a three to five fold molar excess of the cheap carboxylic acid is enough for good yield for Fischer esterifications in my experience. salicylic acid is very cheap and available on amazon, and I have a whole kg of it.

The point of the toluene solvent is that it allows you to use a large excess of salicylic acid, which normally is impossible because it's a solid.
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Syn the Sizer
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[*] posted on 7-3-2020 at 09:38


I think a setup like I had in my piperine extraction might work as work around for a dean stark apparatus, its a little more labour intensive because you would need to drain water then drain toluene since it won't spill back, but it is better than nothing.

https://www.sciencemadness.org/whisper/viewthread.php?tid=15...

Edit: I hindsight this might not work.


[Edited on 7-3-2020 by Syn the Sizer]
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j_sum1
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[*] posted on 7-3-2020 at 14:48


If you buy quart volumes and collect your toluene waste for reuse, I don't think scale is the problem you imagine, Cou. Simply wait until you have 500mL to recycle and do a larger batch.
You won't regret having a DS trap in your glass collection in any case.
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G-Coupled
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[*] posted on 8-3-2020 at 01:33


Quote: Originally posted by Cou  
toluene is kind of expensive, $22 for one quart.... i can get xylene for $10 a quart


Hunh, it's always been the other way round IME (EU) - that Xylene is about that much more expensive than Toluene.
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