Cooperation
Harmless
Posts: 4
Registered: 17-2-2014
Member Is Offline
Mood: No Mood
|
|
What's the best way to separate xylenes and ethylbenzene?
I have some store bought xylenes which also contains ethylbenzene. From researching on the internet, I've discovered that ethyl benzene BP is 136C
and xylenes is from 138-142 (depending on which alphabet-xylene we are wanting). There seems to be a an extraction distillation that can be
performed, but I don't know what the extraction solvent should be. When I fractionally distill the thermometer above the vigreux column doesn't read
correctly, so been monitoring the oil bath instead. This has worked for separating liquids that vary 20-25 degrees from each other, but I'm not
confident in my skills to separate two substances that are so close to each other. Can I use the xylene as it is? Leave the ethylbenzene in there?
Will it affect yield? Should I dry the solvent with magnesium sulfate? Any and all suggestions are welcome.
|
|
|
Ozone
International Hazard
Posts: 1269
Registered: 28-7-2005
Location: Good Olde USA
Member Is Offline
Mood: Integrated
|
|
Getting to -48°C shouldn't be too hard (you can fractionally freeze the isomers out):
Ethyl benzene: MP = -95°C
o-xylene: MP = -24°C.
m-xylene: MP = -48°C
p-xylene: MP = 13.2°C.
Depending on what you want to do, it probably can be used as-is. What is your intent?
--O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
|
|
|
Cooperation
Harmless
Posts: 4
Registered: 17-2-2014
Member Is Offline
Mood: No Mood
|
|
Never thought about freeze separation---great idea
I'm using it as a solvent for a freebase amine prior to Changing the freebase to a HCL salt (via Bubbled HcL gas through Nacl/H2SO4). If you don't
think it will affect yield I won't waste the time separating it. I have fractionally distiller a few things under vacuum but i don't think I have the
skills yet to do this will boiling points so close. Plus, cold seems less dangerous. What's the best way to get down to -48 to -50? I assume once I
freeze the xylenes, the ethylbenzene will stay liquid, and I just lift the frozen chunk of xylene out and I'm good. Really clever, and thanks for the
help!
|
|
|
thesmug
Hazard to Others
Posts: 370
Registered: 17-1-2014
Location: Chicago, Il (USA)
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by Cooperation  | | I'm using it as a solvent for a freebase amine prior to Changing the freebase to a HCL salt (via Bubbled HcL gas through Nacl/H2SO4). If you don't
think it will affect yield I won't waste the time separating it. I have fractionally distiller a few things under vacuum but i don't think I have the
skills yet to do this will boiling points so close. Plus, cold seems less dangerous. What's the best way to get down to -48 to -50? I assume once I
freeze the xylenes, the ethylbenzene will stay liquid, and I just lift the frozen chunk of xylene out and I'm good. Really clever, and thanks for the
help! |
Just for future reference, remember that it is HCl, not HCL or HcL 
|
|
|
crazyboy
Hazard to Others
Posts: 436
Registered: 31-1-2008
Member Is Offline
Mood: Marginally insane
|
|
Ethylbenzene won't be a problem for what you're doing. Furthermore I imagine there is only around 1-5% ethylbenzene present and between freezing point
depression and such a low temperature I don't think fractional freezing would be particularly effective.
|
|
|
Cooperation
Harmless
Posts: 4
Registered: 17-2-2014
Member Is Offline
Mood: No Mood
|
|
Thanks for the help Everyone
I am relieved to know I can use it as is, but I think I will try a freeze separation if I have time since its such a COOL idea (lol...sorry, I
couldn't resist!)
|
|
|
Random
International Hazard
Posts: 1018
Registered: 7-5-2010
Location: In ur closet
Member Is Offline
Mood: Energetic
|
|
I have xylene isomer mixture and when it's under 13 celsius it never precipitates frozen p xylene. It's not as simple.
|
|
|
testimento
Hazard to Others
Posts: 351
Registered: 10-6-2013
Member Is Offline
Mood: No Mood
|
|
Freezing temp of water decreases substantially with only minor amounts of alcohols or chlorides and yet they end up mushy fluff when cooled enough so
separation may not be just as easy as removing a frozen brick of xylene from ethylbenzene. 
|
|
|
leu
Hazard to Others
Posts: 368
Registered: 13-10-2005
Member Is Offline
Mood: No Mood
|
|
Vacuum sublimation is often used to purify aromatic hydrocarbons prior to freeze crystallization The tarry impurities from petroleum processing prevent nucleation from occurring  The attached article titled Separation of para-xylene from xylene mixture via
crystallization may be helpful 
[Edited on 18-2-2014 by leu]
Attachment: Separation of para-xylene from xylene mixture via crystallization.pdf (448kB)
This file has been downloaded 3706 times
Chemistry is our Covalent Bond
|
|
|
Nicodem
|
Thread Moved
18-2-2014 at 06:39 |
Cooperation
Harmless
Posts: 4
Registered: 17-2-2014
Member Is Offline
Mood: No Mood
|
|
I'm not worried about the xylene isomers, just the ethylbenzene
As long as I can use dry ice and freeze the xylenes as a solid block, I'm not worried about the xylene isomers. I'm looking forward to learning this
new technique!
|
|
|
DraconicAcid
International Hazard
Posts: 4278
Registered: 1-2-2013
Location: The tiniest college campus ever....
Member Is Offline
Mood: Semi-victorious.
|
|
| Quote: Originally posted by Cooperation | | As long as I can use dry ice and freeze the xylenes as a solid block, I'm not worried about the xylene isomers. I'm looking forward to learning this
new technique! |
I doubt it's going to work very well, since the xylenes will be quite soluble in ethylbenzene well below their freezing points. You may get some of
the para-xylene precipitating (either as a lump or slush), but the other two will probably stay in solution.
I don't think the ethylbenzene will interfere with the reaction you're trying to do anyway.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
