Deathtillation
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Vapor adsorption with molecular sieves
Dear readers,
Is it possible to replace the dry ice trap with an adsorption tube filled with , for example, 5A sieves when evaporating residual chloroform or
dichloromethane from the organic solution, to protect the membrane vacuum pump from the corrosive vapor of these solvents?
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Dr.Bob
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Not really, a cold trap will work pretty well even at low pressures, but gases in sieves and other absorbents are in equilibrium, so under vacuum the
gases tend to outgas. That is why you can dry Mol Sieves under vacuum (although applying heat makes it much quicker.) However, a membrane pump may
not be damaged by traces of low MW solvents like an oil pump would be, so it may not need protectuino against solvent as much as it does from acid
(and a basic trap WOULD work for removing certain acids.)
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shagydeep
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Hello,
It is possible to replace dry ice but if the vacuums are good and low absorbents then it create much better to suction for the gas...
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