Sciencemadness Discussion Board

NMP - Purification - Ideas?

unome - 4-3-2010 at 06:09

I am having an absolute bastard of a time trying to work out a decent road to purifying NMP (from low-odor paintstripper).

N-MethylPyrrolidone is a dipolar, aprotic solvent (ie. same class as DMF & DMSO), and it is easily acquired, albeit in a seriously nasty polymer forming emulsion.

The gel that it is in appears to be similar to that in the DMC (used for the same applications), but the problem is that NMP is seriously water soluble (data sheet). That kind of complicates things somewhat...

As does the presence of the gelled crap with it - it has a decently high bp (202'c 1atm), which is well and truly within range, but it is going to leave one hell of a mess on glassware when that fucking gunk lets left behind. Not so big an issue with DCM, it boils at a little over room temperature.

Anyone got any ideas? I've looked even at the patents (and some papers) on recycling it, but they all use multi-stage distillation @ reduced pressure, which is what I'm trying to avoid (reduced pressure = glassware + gunk, while heat = solvent container and homemade condenser, plus a crapload of tar-gunk).

Anything that is going to salt it out? Or cause phase-separation? I'd dearly love to avoid distilling it with the gunk in it.

gardenvariety - 4-3-2010 at 06:17

Is the gel/junk water soluble? If not, it seems like dissolve the NMP in water, then freeze or distill out, is the obvious solution.

What is the gel, exactly?

Eclectic - 4-3-2010 at 07:13

Try mixing a small bit with equal part isopropanol, then add salt.

Hopefully the gel will stay in aqueous layer and the NMP will salt out with the isopropanol.

unome - 5-3-2010 at 05:36

I'm reading around the traps, apparently butanol, and other alcohols are added to improve the miscibility of the goop and to prevent phase-separation (must be the polymer that is trying to push the NMP out of solution for mine)... So CaCl2 should be useful (based on experience with EtOAc), it will grab the alcohols and salt out - HOPEFULLY;)

The gel is probably a water soluble polymer, quite possibly one of the normal ones, either a cellulose or even PVP, either way it forms quite a funky gel. As an aside, this stuff smells GOOD, as solvents go, it should be quite nice to work with odour-wise.

[Edited on 5-3-2010 by unome]

Panache - 24-3-2010 at 21:49

Sorry is there a reason you don't just vacuum distill it from the goop?

The_Davster - 24-3-2010 at 22:25

This is where the construction of apparatus from metal pipe parts comes in handy. A cheap metal still body could easily be replaced, and allow you to separate the NMP.

unome - 25-3-2010 at 01:31

No real reason I can't just vacuum distill it from the crud - I just dislike the idea of fucking hard-to-replace glass, which is pretty much necessary for the Vacuum Distillation. Realistically, 200'C and atmospheric distillation is probably a more realistic choice, the distillation could then be done in steel/copper vessels (even the solvent can it comes in, most of the time anyway).

I'm spending everything I can get on components for the spectrometer idea (plus a shitload of time)...

Be back to this soon:P

Panache - 30-3-2010 at 16:42

a standard 1, 2, 3, 4, 6 or 9kg/L bbq/camping/propane/lpg gas cylinder has a fitting that can be easily adapted to accept a b19 or b24 maLE socket, just use teflon tape to build up the glass socket/round glass joint, after this use the vessel as you would a glass one of the same volume, however remember it is mild steel and as such won't like acids much, so neutralise anything that goes in it.
Voila!!

mr.crow - 30-3-2010 at 17:49

NMP looks like a great solvent to replace DMSO, which degrades after a few years.

When I was a kid I used a BBQ tank to store air for a potato cannon. They have a standard 3/4 inch thread. It stank every time it fired, so that's not a good idea!

On that youtube channel where he makes the ton of chloroform he also uses an old freon tank to distill benzene. Maybe this would be better.

http://www.youtube.com/watch?v=sYyw_hrXrZ8

It would be easy to make the whole setup out of copper, no need for glass adapters. Maybe just one for the receiving flask.

Panache - 6-4-2010 at 16:45

Quote: Originally posted by mr.crow  
NMP looks like a great solvent to replace DMSO, which degrades after a few years.

When I was a kid I used a BBQ tank to store air for a potato cannon. They have a standard 3/4 inch thread. It stank every time it fired, so that's not a good idea!

On that youtube channel where he makes the ton of chloroform he also uses an old freon tank to distill benzene. Maybe this would be better.

http://www.youtube.com/watch?v=sYyw_hrXrZ8

It would be easy to make the whole setup out of copper, no need for glass adapters. Maybe just one for the receiving flask.



I would assume that after stripping the nmp from the 'goop' a second more careful distillation from glass with a column would be needed. I assume this would also take care of the thio's hanging around from the vessels days as a lpg/propane vessel.

That video is the most professional 'jerry job' i have ever seen, if i could jerry things up that neatly i'd video my work also, lol.

'Do it proper do it in copper', but you have to be able solder well, something i can't manage to master (i can't even solder electrical connections very well, maybe 2/5 attempts hold, ha i love it that all humans are just really shit at something no matter how hard they try at it.)

chemrox - 14-4-2010 at 23:45

looks like a fun molecule for making Schiff bases and running annelation reactions to build heterocycles. Can you get a MSDS for the product? That would help in developing a separation strategy. BTW toluene is sold in cans at the hardware store and most of us use a lot of DCM. Both of these irritate the liver. It was a cold winter where I live and I was remiss in not ventilating enough although my system can move a lot of air. I'm now taking a lot of milk thistle and using gloves meticulously as well as running my fans whenever I'm working in the lab. Pay heed; high sgot & sgpt are no joke!

densest - 15-4-2010 at 16:11

@panache - flux is the key to soldering copper, steel, aluminum, and any other metal forming an oxide film. Electrical joints need a rosin-type flux with only organic acids. Aluminum needs special fluxes - fluorides? Stainless steel needs fluoride flux or something equivalent, though zinc chloride works for many alloys. The solder will only flow where the metal has been cleaned & fluxed. Pipes need to have the outer oxide layer removed with fine abrasives like 300 grit aluminum oxide. Then add flux fairly liberally and heat. Touch the solder to the joint but don't add it until it starts to flow. Add solder quickly and evenly - it will flow towards the heat. Once the solder starts flowing well distribute the heat and solder over the joint.

Flexible mains cord is very difficult to solder. Most power connections should use crimped connectors applied with a crimping tool not pliers. That is considerably more reliable than soldering.

@unome - why can't you vacuum distill in metal? If you need to block heat transfer, stainless steel is close to a heat insulator. Copper pot, stainless elbow, copper condenser with stainless tee to vacuum and output flask. Compression fittings can bridge metals and allow disassembly. Some of the fittings are specialized and can be found on EBay etc. at reasonable prices (a few $ each) and with a teflon (lowish temperatures) or copper (higher temperature) washer are gas tight and vacuum tight. I forget the name of the fitting type - it's the original manufacturer's name. You can use silver solder for any area that gets really hot. That requires the joints be very close fitting and heated well so you use a very tiny amount.

not_important - 16-4-2010 at 02:12

Something to consider when considering fabbing a metal still for NMP
Quote:
NMP does not react with most metals, including steels, aluminum, nickel, silver, gold, chromium and chromates, copper, tin, and silicon. However, it should not be used with bronze or brass valves in process piping.


I've been told that when hot it will slowly react with copper to some extent when O2 is present, but I've not seen any formal data on this.

mr.crow - 16-4-2010 at 06:43

While we are on the topic of NMP, would it be possible to synthesize it? The synthesis I found uses GBL, no thanks!!!

My theory is monosodium glutamate from the grocery store can be decarboxylated to GABA, and then the ring closed to form the amide pyrrolidone (how?). But then the n-methyl is missing and would be too much trouble to add. Pyrrolidone may be just as effective a solvent.

not_important - 16-4-2010 at 07:35

Glutamic acid easily cyclises to pyroglutamic acid (2-oxo-pyrrolidone carboxylic acid, 5-oxoproline, a recent source of e-spam), even in hot water to some degree. The mono N-methyl acid does so as well, and can be prepared mixed with the N-dimethyl acid using oxalic acid and paraformaldehyde; as the di-Me acid can not cyclise separation is not too difficult.

But NMP is an industrial chemical manufactured on a large scale, and increasingly being used as a cleaning solvent. I suspect it's not worth the effort and cost of preparing it from MSG.

mr.crow - 16-4-2010 at 09:43

NMP is actually super expensive from Fishersci. Maybe it is much cheaper for technical grade from another supplier.

Oh I found this :) http://www.greenbuildingsupply.com/utility/showProduct/?obje... good luck getting rid of the PVC resin though

Does pyroglutamic acid decarboxylate easily? Then it is a simple procedure to prepare your own polar aprotic solvent.

bahamuth - 14-5-2010 at 07:48

I found one type of paint stripper which they sell in Scandinavia from Biltema, and the MSDS was easily found. http://biltema.no/Documents/faktablad/36-018.pdf

Begun extraction just for the fun of it after reading this post.

The first thing I tried was centrifuging at 21000 G's for 60 min. in eppendorf tubes, microscale. This yielded about 35% of clear supernatant and the rest a very viscous gel.

The polymer in this gel is Polyacrylic acid, which I figured might have similar properties as Sodium polyacrylate in accordance to the destruction of the gel properties in Sodium polyacrylate by the action of Sodium chloride http://depts.washington.edu/chemcrs/bulkdisk/chem142A_aut05/...

Further I added a pinch of Sodium chloride to the remaining gel in the tubes, mixed as good as possible and spun it for another 20min at 21000 G's, and ended up with about 10% more supernatant, yielding all in all about 45% of supernatant.

Scaled this up to 50mL tubes skipping first step and just added salt and spun at 6000 G's for 10 min and got a semi solid as lower phase and a clear liq. supernatant. Noticed that at those speeds; micro fissures formed in the 50mL tubes, rated at 16000 G's; wetting the tube on the outside. Yield appeared better than the above microscale approach, but did note take measurements.

Then the real problem, which I haven't got to yet, the separation and purification of the NMP.

Will post my findings on a later occasion.

Also, any suggestions on how to improve extraction and separation is welcome; do have opportunity to vacuum distill but wanted another approach with less work and cleanup.


PS. The MSDS gives wrong "chemical name" for the NMP, but correct CAS and INCI name, as do the container.

Panache - 21-5-2010 at 20:44

Quote: Originally posted by bahamuth  
I found one type of paint stripper which they sell in Scandinavia from Biltema, and the MSDS was easily found. http://biltema.no/Documents/faktablad/36-018.pdf

Begun extraction just for the fun of it after reading this post.

The first thing I tried was centrifuging at 21000 G's for 60 min. in eppendorf tubes, microscale. This yielded about 35% of clear supernatant and the rest a very viscous gel.

The polymer in this gel is Polyacrylic acid, which I figured might have similar properties as Sodium polyacrylate in accordance to the destruction of the gel properties in Sodium polyacrylate by the action of Sodium chloride http://depts.washington.edu/chemcrs/bulkdisk/chem142A_aut05/...

Further I added a pinch of Sodium chloride to the remaining gel in the tubes, mixed as good as possible and spun it for another 20min at 21000 G's, and ended up with about 10% more supernatant, yielding all in all about 45% of supernatant.

Scaled this up to 50mL tubes skipping first step and just added salt and spun at 6000 G's for 10 min and got a semi solid as lower phase and a clear liq. supernatant. Noticed that at those speeds; micro fissures formed in the 50mL tubes, rated at 16000 G's; wetting the tube on the outside. Yield appeared better than the above microscale approach, but did note take measurements.

Then the real problem, which I haven't got to yet, the separation and purification of the NMP.

Will post my findings on a later occasion.

Also, any suggestions on how to improve extraction and separation is welcome; do have opportunity to vacuum distill but wanted another approach with less work and cleanup.


PS. The MSDS gives wrong "chemical name" for the NMP, but correct CAS and INCI name, as do the container.


How many 50ml tubes can you spin at a time? The graffitti remover available in australia is simply a mix of solvents, no gel and about 75%NMP so we have life a little less bothersome. That said it does cost ~$AU30 for 500mL so not cheap but everywhere sells it.

Perhaps you may be able to blow out the NMP from the gel with a fine bubbler running air, nitrogen or argon at say 80C, the carrier gas takes anything volatile with it. The gas is then cooled forming a fog which is laden with the volatiles. i believe the technique is called 'insert name of carrier gas used' stripping. The 80C i just guessed at, if you have a dew pointer it would help you with setting the experiment up. If you want further info on this let me know as i have been meaning to do a lit review on the state of the art and this may inspire me. Is it used industrially AFAIK for stripping ethanol out of low alcohol fermentation mashes using nitrogen at 30C and this is the purpose i am interested in.

As for the cracked tubes where they brand new or ad some tech washed them int he dishwasher clucking them together repeatedly?

bahamuth - 22-5-2010 at 07:15

I can spin 6 50mL tubes at once, but have not scaled up yet.

Discovered something about the gel, if Sodium chloride is mixed with the paint stripper and frozen, the gel falls out and should give a larger yield but have not had time to do more..

Also have access to a Sorvall centrifuge which goes up to 50000 G's and takes 6 times 300mL but have not tried it yet...

Melgar - 22-5-2010 at 07:35

I would try getting a big glass liquor bottle and using silicone caulk or something similar to attach it to a glassware vacuum distillation column. As long as heat is applied relatively slowly, I've found that the glass that food and drinks comes in is actually quite durable. Then just throw the bottle away, tar and all.

MrG - 26-9-2018 at 02:57

Ok so has someone extracted gbl successfully from nmp mix? Can I use a lab freezer for fractional freezing to a solid and removing?

MrG - 26-9-2018 at 03:06

duplicate post

[Edited on 26-9-2018 by MrG]

MrG - 26-9-2018 at 06:18

???

[Edited on 26-9-2018 by MrG]

Dr.Bob - 26-9-2018 at 07:08

Its really hard to purify NMP and get it dry. If you can find any source of the pure material, it will help a lot, as it is one of the hardest solvents to purify or dry easily. But it is a great solvent for some reactions, such as amide formation (eg, peptides on resin) and some specialized ones, like alkylations. But often the workup is to dilute with water to ppt the product, which makes it nearly impossible to recover the NMP. If you look, someone on Ebay or other place will sell it.

MrG - 26-9-2018 at 07:36

Quote: Originally posted by Dr.Bob  
Its really hard to purify NMP and get it dry. If you can find any source of the pure material, it will help a lot, as it is one of the hardest solvents to purify or dry easily. But it is a great solvent for some reactions, such as amide formation (eg, peptides on resin) and some specialized ones, like alkylations. But often the workup is to dilute with water to ppt the product, which makes it nearly impossible to recover the NMP. If you look, someone on Ebay or other place will sell it.



I want to remove NMP from GBL. Could I do this by freezing nmp to its melting point?

Dr.Bob - 27-9-2018 at 12:22

Quote: Originally posted by MrG  
I want to remove NMP from GBL. Could I do this by freezing nmp to its melting point?


Not likely. People need to remember that mps are defined for PURE compounds, once a compound is mixed, the mp is depressed, often completely eliminated. It is one thing to crystallize tBuOH from the liquid to purify it, but trying to freeze out one solvent from another only works in a few cases, almost impossible in many cases. The more similar two solvents are, the harder it would be to freeze one out. Also, in general crystallizations work best with nearly pure material to get it really pure, not so well with 50:50 mixtures.

If the NMP bp was much different than GBL's, so you might be able to distill away the GBL away from the NMP, then once the NMP is mostly pure, you could try to vacuum distill it a second time to purify it. But they are much closer in bp than I would have guessed, only 4 degree F apart. Distillations are affected by mixtures as well, but they work pretty well when the bps are more than 10-20 C apart. But with only 2 C between them, they will be very hard to separate that way.

Metacelsus - 28-9-2018 at 04:55

If you don't have a good enough column, you might be able to selectively hydrolyze the GBL, distill off the NMP, and then do an esterification to recover the lactone. However, this probably wouldn't be very economical.

(Of course, if you're just after the lactone hydrolysis product, then this method would be more attractive. But be careful to not do anything you'll regret.)