Chemguy5
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Dissolving molecular sieves!!??
I recently (approx. 5 days ago) extracted DCM from paint stripper by distillation. The paint stripper was a combination of DCM and Methanol. After I
distilled off the DCM from the stripper I poured it into a sep. funnel and washed with dh2o untill I removed all the Methanol from the DCM. I then
dried the DCM with MgSO4 and after letting sit for a good 20min I then poured the dried DCM through a few coffee filters into its final container.
As I was doing all this I had molecular sieves drying in the oven on 400-500F for around an hour. Once sufficiently dry I let them cool and added them
to the DCM. Once added I noticed VERY tiny bubbles comeing off the sieves indicating residual water being absorbed by the sieves. So far so good. I
placed the bottle on my desk for the next two days occasionally shaking and did not notice anything out of the ordinary. I then placed the bottle into
a cooler where I keep some of my other chems.
Now today (3 days later) I just opened it up and noticed 2 very clear clean layers had formed??? I then noticed most of all the sieves had
disappeared!!!! Indicating they had dissolved into the DCM?!?! I have never seen this before nor have I had a problem like this with these sieves.
The sieves were purchased from eBay about a year ago and they where fairly cheap. If I remember correctly I meant to purchase 3A molecular sieves but
I believe by mistake I ordered 4A. Now I'm not 100% certain about this but for some reason I think I remember them being labeled as 4A but I can't be
positive. Any way when I purchased the sieves I did a test by drying them first in the oven and then I took a small beaker and filled it with dh2o. To
the beaker I added the pre dried sieves and a thermometer to record the temp. According to NURDRAGE video if a substantial rise in temp is seen when
the sieves are added to water then they work pretty good. I performed this experiment again but with pure Methanol only and did not notice such a high
jump in temp like I did with the H2O.
Any ideas on what is going on here?? Please I'm all ears and would like to know what happened. I am going to try and distill off the DCM now hopefully
I can get it back.
Are molecular sieves soluable in DCM?!
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TheMrbunGee
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To my knowledge - sieves are made from materials that does not dissolve in any solvent (like clay, glass and other silicates)
So either you got scammed or the sieves have finally escaped.
EDIT: Are there any powder in your DCM, maybe they crumbled or something. may be you have picture? You can repeat your actions and observe what is
going on.
[Edited on 28-9-2018 by TheMrbunGee]
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Chemguy5
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No powder what so ever... two crystal clear layers with only a few sieves left on bottom. I don't have any pictures, I actually ended up distilling
and collecting the DCM again. It is so strange tho I can't figure out what happened. Unless some one broke into my house and stole some of the sieves
out of the bottle and poured some water in lol I don't know what happened. They were not fake sieves either because I used them before on other
solvents and most likely DCM as well and never has this happened....
wow...my mind is blown...
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TheMrbunGee
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Quote: Originally posted by Chemguy5  | No powder what so ever... two crystal clear layers with only a few sieves left on bottom. I don't have any pictures, I actually ended up distilling
and collecting the DCM again. It is so strange tho I can't figure out what happened. Unless some one broke into my house and stole some of the sieves
out of the bottle and poured some water in lol I don't know what happened. They were not fake sieves either because I used them before on other
solvents and most likely DCM as well and never has this happened....
wow...my mind is blown... |
Can you repeat a small scale test, if that happens again? And what was the remaining solution? Did you inspect it? is there any possibility, that
alkali hydroxide was in your DCM and sieves?
I am really curious of what happened there..
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Metacelsus
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If it does indeed dissolve sieves, why would it leave a few sieves behind? I would expect either:
1) no sieves dissolve
2) all sieves show partial dissolution
or
3) all sieves dissolve
Having some fully dissolved sieves and some undissolved sieves doesn't make a lot of sense.
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Chemguy5
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I agree, but possibly the last of the sieves hadn't yet dissolved ? I had a good 1.5-2 inches of sieves piled up from the bottom of the container and
when I took it out from the cooler there was litterally maybe 20-30 sieves left in the container...
After I distilled off the DCM I was left with a clear water phase and just dumped it into my waste container. I should have kept it but I'm in the
middle of another experiment.
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macckone
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It is possible for sieves to be made of something other than silica/alumina/zeolite but the ones that are based on organics wouldn't leave a water
layer.
I have seen things labeled incorrectly where instead of sieve it is actually a calcium chloride with clay, which work fine until you put them in
something containing a lot of water or alcohol. But those leave a powder of clay on the bottom. Nor should your DCM have had that much water after
drying with magnesium sulfate.
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happyfooddance
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I have distilled paint stripper from a half full can with boiling chips thrown in and then washed the distillate with several portions of water+CaCl2
(to remove MeOH by formation of a complex), dried over CaCl2 and then redistilled through a column, and there was a residue left in the boiling flask.
Maybe your stripper has the same contaminant since it was prepared similarly, and maybe this contaminant is reacting strangely with your sieves? I
don't know what it is because I didn't do any testing on it, but I read somewhere that it might be a polymer of some sort.
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