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Author: Subject: Effective antifoaming agents used with organic solvents
chemoleo
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[*] posted on 25-1-2011 at 18:49
Effective antifoaming agents used with organic solvents


Can anyone recommend one?
Preferably it is unreactive, i.e. tolerated by acylations.
Solvents I'm thinking of are DMF, DCM, NMP, including non-nucleophilic bases.
Silicone polymers seem the material of choice, but there are so many, perhaps someone has some experience and/or advice?

For instance, what do you think of this stuff
http://www.sigmaaldrich.com/catalog/ProductDetail.do?lang=en...

Sadly they don't give a structure - it'd help!




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Magpie
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[*] posted on 26-1-2011 at 00:15


Where I worked in industry Dow defoamers were used successfully on paper pulp washers and in a brine evaporator.

This MSDS may help in determining the main ingredient:

http://www1.dowcorning.com/DataFiles/090007b281460737.pdf




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chemoleo
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[*] posted on 26-1-2011 at 14:41


THanks- but I'm more after an antifoamer that is already anhydrous, and explicitly useful for organic solvents.
The scenario is, a reaction vessel receives constant N2 bubbling, but at times it foams so much that reactants come out at the top end.
Easy, you'll say, just reduce the N2 flow- but that isn't easily done - plus the N2 is required to for mixing. So I thought an antifoaming agent might be the smartest solution...




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[*] posted on 26-1-2011 at 14:59


Mechanical - if your reaction setup involves ground glass joints, employ a foam breaker:



You can also reduce foaming by lowering surface tension of the liquid. I sometimes add dichloromethane, hexane or diethylether for rotary evaporation of foamy solvents. But with N2 bubbling they'll be gone quite quickly.




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Magpie
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[*] posted on 26-1-2011 at 15:38


Chemoleo, I wasn't so much thinking that the Dow product per se would be what you're looking for but the silicone name might be of use, eg, polydimethylsiloxane, etc.

Here's one for the oil & gas industry that is specifically all organic:

http://www.dowcorning.com/applications/search/default.aspx?R...




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