Sciencemadness Discussion Board

Dissolving molecular sieves!!??

Chemguy5 - 27-9-2018 at 18:08

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?!

TheMrbunGee - 27-9-2018 at 23:19

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]

Chemguy5 - 28-9-2018 at 01:10

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...

TheMrbunGee - 28-9-2018 at 02:10

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..

Metacelsus - 28-9-2018 at 04:48

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.

Chemguy5 - 28-9-2018 at 05:07

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.

macckone - 28-9-2018 at 06:34

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.

happyfooddance - 28-9-2018 at 13:15

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.