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Author: Subject: Separating OTC Xylene
Syn the Sizer
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[*] posted on 14-1-2022 at 11:59


There are several sources that only show an azeotrope for m-xylene but this is the first claim I have ever heard for the o- and p- isomers.

xylene is never used for removal of water because the p- and o- isomers do not for an azeotrope. Here are four links and feel free to google more. As I said before the info on the paper is flawed, as I know there is no azeotrope for o- and p- isomers and pure water and as the book is only available for $400 I cannot check their reference to see if they screwed up writing their paper of if that book has some misinformation

https://en.wikipedia.org/wiki/Azeotrope_tables

https://rushim.ru/books/spravochniki/azeotropic-dataII.pdf

http://homepages.ed.ac.uk/jwp/Chemeng/azeotrope/hetero.html

https://archive.org/details/006.azeotropicdata1952/page/n11/...


While writing this reply I was scouring the web for info on the topic, here is this website

https://www.wikiwand.com/en/Xylene

that claims an azeotrope of mixed xylenes and water which references this paper

https://sci-hub.yncjkj.com/10.1002/14356007.a28_433

which clearly states only ethylbenzene and m-xylene

I can almost guarantee it will only be the m- that comes over as there is only 2 sources that claim mixed xylenes, one referenced a paper linked above which debunks their claim showing they did not read properly and another paper which references a book we cannot get, for all we know there was a trick to them getting all 3 isomers such as reduced pressure or such but we cannot tell without the book in reference, every other source lists only the m- isomer.

Syn'

[Edited on 14-1-2022 by Syn the Sizer]

[Edited on 14-1-2022 by Syn the Sizer]
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SWIM
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[*] posted on 14-1-2022 at 14:54


Meltonium tried azoetropic separation of xylenes with water and had poor results, but it was a nice write-up.

Ethylbenzene is a bit more water soluble than the xylenes, so you might be able to just run the stuff for days and days in a continuous liquid/liquid extractor and get ethylbenzene free xylenes.
Probably lose a lot of xylenes in the process too, but they are cheap.

I've seen claims that distilling at about 40 theoretical plates to get the Para and ortho xylenes separated from the meta can be followed by fairly efficient freezing out of the para isomer.(not that this helps with the ethylbenzene problem, but I do find it interesting)

However I have never tried it out personally. (I really need a better small-scale distillation head)




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Syn the Sizer
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[*] posted on 14-1-2022 at 16:17


Quote: Originally posted by SWIM  
Meltonium tried azoetropic separation of xylenes with water and had poor results, but it was a nice write-up.

Ethylbenzene is a bit more water soluble than the xylenes, so you might be able to just run the stuff for days and days in a continuous liquid/liquid extractor and get ethylbenzene free xylenes.
Probably lose a lot of xylenes in the process too, but they are cheap.

I've seen claims that distilling at about 40 theoretical plates to get the Para and ortho xylenes separated from the meta can be followed by fairly efficient freezing out of the para isomer.(not that this helps with the ethylbenzene problem, but I do find it interesting)

However I have never tried it out personally. (I really need a better small-scale distillation head)


Right I forgot about the freezing point difference lol, they were even mentioned in an earlier post, with just the 2 isomers it would have a better chance of freezing one out as compared to all 4 components.

The idea is neat to be able to remove the ethylbenzene or isolate the isomers at home, but for me it always comes to a few factors, is it fun enough to spend the time, is it worth it in the end or can I use the OTC product for what I am doing, and the final is cost of time + OTC products + electricity (my time is money even when working for myself) as compared to the cost of the isomer I desire or ethylbenzene free xylenes from a shop online.

Often buy the reagent I need wins.
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teodor
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[*] posted on 15-1-2022 at 06:31


Quote: Originally posted by Syn the Sizer  
There are several sources that only show an azeotrope for m-xylene but this is the first claim I have ever heard for the o- and p- isomers.

https://en.wikipedia.org/wiki/Azeotrope_tables


This source quotes ACS tables and a paper that study only azeotropes of m-xylene.
As for ACS tables, as I already wrote, they usually have a special row "noazeotrope" for compounds which doesn't form an azeotrope. So, the absence of a compound (e.g. o-,p-xylene) in the ACS table doesn't necessarily mean the compound doesn't form an azeotrope.

Quote: Originally posted by Syn the Sizer  

https://rushim.ru/books/spravochniki/azeotropic-dataII.pdf


This is actually ACS table, the first reference cited by Wikipedia. So, this is not additional source of the information.

Quote: Originally posted by Syn the Sizer  

http://homepages.ed.ac.uk/jwp/Chemeng/azeotrope/hetero.html


This doesn't look like a reference.

Quote: Originally posted by Syn the Sizer  

https://archive.org/details/006.azeotropicdata1952/page/n11/...


This is again the same ACS table. So, those 3 links is actually 1 reference.

It would be interesting to look either on a paper that does actual study the topic (like that one you don't trust to, but at least there is an experiment and accurate data) or to make an experiment. The difference between m-xylene azeotrope (92C) and the boiling point of other xylenes is enough to check it in a simple setup. But for that, we need pure samples of o- and p- isomers.
My OTC xylene is probably mainly m- isomer, so, it is not suitable for such kind of experiment.

If somebody has pure p- xylene (which is the best for the experiment because the purity is quite easy to check by melting point) and can share it with me, I will try to make the experiment.


[Edited on 15-1-2022 by teodor]
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Syn the Sizer
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[*] posted on 15-1-2022 at 11:13


Quote: Originally posted by teodor  

This is again the same ACS table. So, those 3 links is actually 1 reference.
[Edited on 15-1-2022 by teodor]


Fair enough, I should have dug deeper and checked where they all sourced their data from as well.

The topic started as separating ethylbenzene and degraded into a debate on xylene azeotropes.

Not to mention I am done anyway, this topic has exhausted my interest period, I literally have 0 interest in separating ethylbenzene or any of the isomers. If I ever need it pure I will just buy it pure plain and simple.

If I need the isomer for oxidation to a phthalic acid I will just buy the isomer of phthalic acid I need.

Please keep searching and when you find definitive proof that the other isomers form an azeotrope let us know, I am a little bit curious myself too as I have only ever seen that the m- isomer will form an azeotrope, for the knowledge. If that book was available in digital format or somebody had a copy it could be checked. It would be useful for many hobbyists who can't just get toluene OTC for water removal.

This has proven though that you cannot even trust science (which I knew already). All references lead back to 1 source, nobody experiments to test the source, they just trust it, myself included as seen here and if it was published in a paper or book 70 years ago just go with it, don't question, just go with it. Amphetamines are healthy, UVC doesn't cause cancer, the earth is flat, wait, scratch the last one.

Syn'
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