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Author: Subject: Activating/regenerating 3A molecular sieves.
Db33
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[*] posted on 9-12-2016 at 08:59
Activating/regenerating 3A molecular sieves.


My question is, if i order some 3A molecular sieves i know that just being in the air they absorb a ton of moisture. To activate or get them back to dryness they need temperatures of like 300-400C for a few hours i think if i read correctly?

My oven goes to 230C so im wondering how do home chemists go about activating/regenerating their sieves? Would a microwave work, or a bunsen burner?
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Chlorine
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[*] posted on 9-12-2016 at 09:02


There are normally instructions on the bottle/bag about what tempature to heat them.
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Tsjerk
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[*] posted on 9-12-2016 at 09:04


200oC is more than enough
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Db33
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[*] posted on 9-12-2016 at 09:59


for how long?
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Tsjerk
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[*] posted on 9-12-2016 at 12:37


It doesn't come too close, as long as they are dryish it is fine, a couple of hours I would say
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aga
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[*] posted on 10-12-2016 at 12:39


Whichever oven you have (no other exists) full power, 2 hours and they are good to go once they have cooled down to RT.

Test : take a pinch of them in a Gloved hand and squirt some water on them.

They should instantly get VERY HOT and you should instinctively throw them away, rip off the glove, maybe shout some expletives.

If this happens, they are dry enough.




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Khemi
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[*] posted on 11-12-2016 at 02:28
Mol- Sieves


I watched this https://www.youtube.com/watch?v=MduzjhRHBFY and it explained that some china suppliers of mol.sieves sell junk. Check the video for more info.
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[*] posted on 11-12-2016 at 07:52


A Chinese supplier selling junk... Not really something new under the sun I would say.
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Db33
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[*] posted on 11-12-2016 at 08:29


ive noticed thatthe white sieves are always better than the chinese brown sieves. just saying
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[*] posted on 11-12-2016 at 08:42


If you buy super dry solvents from for example Sigma, the beads in the bottle are also brown.

Why do you think the white ones are better? How did you notice there is a difference?
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Db33
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[*] posted on 11-12-2016 at 09:10


I say that because 100% of the chinese ones ive seen are brown and when tested were less reliable than the white.
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[*] posted on 11-12-2016 at 09:14


Quote: Originally posted by Db33  
I say that because 100% of the chinese ones ive seen are brown and when tested were less reliable than the white.

How did you test them if you're asking here about how to activate them ?

None come pre-activated, so Any new ones would do pretty much nothing (apart from make your liquid a dusty brown).




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Chlorine
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[*] posted on 11-12-2016 at 10:09


Quote: Originally posted by Db33  
ive noticed thatthe white sieves are always better than the chinese brown sieves. just saying


Color has nothing to do with how effective seives are.
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careysub
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[*] posted on 11-12-2016 at 13:33


3A sieves sold for filling insulating glass panes DO come preactivated, since the buyer is expecting just to put them into their pane assembly just before sealing. They aren't chemists and will never reuse them.

These are the best priced sieves I have seen BTW. 5 lb for $35 on eBay.




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[*] posted on 11-12-2016 at 21:22


if you are interested Nurdrage released a video not too long ago testing his "cheap Chinese" sieves versus his lab grade sieves just by measuring the change in temperature when exposed to water.

It does show that even the crappy Chinese ones do a surprising "average" job (for the price) nothing compared to lab grade though.
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[*] posted on 11-12-2016 at 23:26


Ok, I didn't see the video but that sounds reasonable. Although it only says something about the speed of absorption and maybe something about the total capacity. But not about total left water (ppm water in solvent after say 24h), which I think won't differ.
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