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Problems wtih Arcing
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kiwichemist
Mon Nov 21 2011, 12:09PM
Registered Member #6350
Joined: Mon Nov 21 2011, 12:01PM
Posts: 1
I am using our microwave synthesiser to perform polycondensation reactions on polyols in the presence of an acid (citric acid) and only trace amounts of water. We have had no problems performing these reactions in a sealed tube or open at atmospheric pressure however when we applied a small vacuum to drive teh reaction by the removal of water we are observing arcing in the reaction vessel. I have been looking into this and found no evidence of similar problems in the literature with the use of microwaves in conjunction with vacuum. Can anyone shed any light on this problem for us.Thanks
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Grace
Tue Dec 13 2011, 02:32AM
Registered Member #13
Joined: Tue Dec 16 2008, 08:13AM
Posts: 12
What you are observing is not arcing, but rather you are forming a microwave plasma. To prevent the plasma from forming you should reduced the amount of vacuum applied to the sample or start with no vacuum and slowly apply the vacuum to the sample after the target temperature has been reached. Alternatively, can you use something like molecular sieves to sequester the water generated?
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phonesystems
Tue Dec 13 2011, 06:53PM
Registered Member #6433
Joined: Tue Dec 13 2011, 06:43PM
Posts: 1
You can very well go with using molecular sieves to remove water but remember not to stir the otherwise solvent may get damaged.
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