Sciencemadness Discussion Board

Separation question

drzdude - 4-3-2018 at 13:00

Hey, I found an OTC product with propylene glycol methyl ether, DCM, and nitroethane, and I’m trying so see what would be the best way to separate the three from each other. DCM can easily be distilled off, but the other two have bp’s very close to one another. Any suggestions for a way to pull the PGME out of solution possibly? Thanks!

Reboot - 4-3-2018 at 14:27

The PGME is reportedly miscible with water, while the nitroethane is only slightly soluble. I would probably hit it with some water (which is likely to cause separation), collect the bottom (organic) layer containing the DCM and nitroethane, then distill it.

DraconicAcid - 4-3-2018 at 15:08

Quote: Originally posted by Reboot  
The PGME is reportedly miscible with water, while the nitroethane is only slightly soluble. I would probably hit it with some water (which is likely to cause separation), collect the bottom (organic) layer containing the DCM and nitroethane, then distill it.


I was going to suggest something along these lines after looking up the solubility of the two. Rather than just "hitting it", you'd probably want to do several extractions with water to get the majority of the PGME out.

drzdude - 4-3-2018 at 16:24

Yeah I saw on wiki it’s miscibility in water, and figured that would be the best bet. But never worked with PGME before so figured I’d check.

Thanks!
Quote: Originally posted by Reboot  
The PGME is reportedly miscible with water, while the nitroethane is only slightly soluble. I would probably hit it with some water (which is likely to cause separation), collect the bottom (organic) layer containing the DCM and nitroethane, then distill it.

Reboot - 4-3-2018 at 17:00

Quote: Originally posted by DraconicAcid  
Rather than just "hitting it", you'd probably want to do several extractions with water to get the majority of the PGME out.


Indeed. :-) I should be more explicit. Since nitroethane is slightly soluble in water (and may only be present in moderate amounts in the feed stock) water volumes should be kept minimal. Add enough to cause separation, then wash perhaps twice with small additional amounts of water (less water than organic layer.)

Although it depends on your ultimate goal. If purity is more important than recovery, larger wash volumes/more washes could be appropriate.

Vosoryx - 4-3-2018 at 17:42

What product is this, if you don't mind me asking?

happyfooddance - 5-3-2018 at 12:15

Nitroethane behaves strangely with water, especially in the presence of other solvents, IME. Look at this datasheet and tell me if you can see what I mean.

https://www.google.com/url?sa=t&source=web&rct=j&...

If I were you, I would formulate as many extraction routes as I could think of, and try them out on a small scale.

I think the statement that nitroethane is only slightly soluble in water should only be taken at face value if you have a centrifuge. Otherwise, it may be safe to say it can form tenacious emulsions with aqueous solutions. If you are doing water extractions, perhaps try adding different amounts of different salts. CaCl2 is one I'd try.

Mostly I am assuming that you are wanting the nitroethane in pure form, since those other two components are much more easily accessible.