RareEarth
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How fast do molecular seives absorb?
I want to use a 4A molecular seive to mop up methanol released by reaction of an amine with methyl ester to form an amide, driving the equilibrium
forward, with the amine source being a 4-carbon amine (not absorbed by seive).
I believe the reaction favors the methyl ester in equilibrium, so the formed methanol would need to be mopped up. Assuming the equilibrium is fairly
rapid and that the rate of the reaction is dependent upon how fast the methanol can be taken out of solution by the molecular sieve, how fast can I
anticipate? I've never worked with molecular seives before.
[Edited on 20-10-2015 by RareEarth]
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aga
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Although the methanol might be favoured by the sieve, it would still be present (not be totally removed) hence still available for the reverse
reaction to occur.
At a guess, this is why reaction schemes are chosen where stuff like methanol can be boiled off to help drive the reaction to completion.
I bought some A4 sieves a while ago and recently threw them away.
Most likely is this because i do not know what to do with them either.
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battoussai114
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I couldn't find it but someone oughta have made a plot of methanol adsorption vs time somewhere. Since I'm currently online using a crappy 3G
connection I won't look much further, you could try a book like "Molecular Sieves: From Basic Research to Industrial Applications" or something along
these lines...
Now, from my understanding the adsorption equilibria is mostly affected by temperature (though as with most of science there's a ton of other stuff
that would make it deviate from the expected behavior), you may want to try and keep the temperature of a methanol solution similar to the one in your
reaction and titrate samples of it for methanol concentration from time to time in order to establish how this goes.
I'm not familiar with the mechanism of the reaction you're performing, so I'll just throw here that 4A sieves are made of alumina with sodium ions,
and it may exchange it's ions and/or be attacked depending on what kind of catalyst goes in this reaction.
Batoussai.
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Magpie
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I think the rate of absorption is going to be concentration dependent. Effectiveness for your application will also be dependent on how low a
concentration of methanol you have to reach and how fast you have to reach this level.
I have a paper with data on the effectiveness of 3A sieves for removing water to ppm levels. The levels are dropping daily over a 4 day period.
The single most important condition for a successful synthesis is good mixing - Nicodem
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