LRM
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Ammonium bromide route for rare earth bromides
I was looking at this paper and the process it describes for the production of rare earth bromides but I was wondering if someone could give me an
idea why the paper says "CeO2, should not be used".
THE AMMONIUM-BROMIDE ROUTE TO ANHYDROUS RARE EARTH BROMIDES MBr
They unfortunately do not elaborate on why CeO2 should not be used but I would love to know. This might be wishful thinking but all that make sense to
me would be that they are trying to say the +4 oxidation state of CeO2 would not work and to instead use Ce2O3.
Am I missing something here?
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Boffis
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CeO2 will almost certainly oxidize bromide ions to bromine which will then contaminate the product. I would have thought that terbium oxide and
praseodymium oxides will react similarly. Terbium oxide slowly liberates chlorine as it dissolves in hot hydrochloric acid.
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LRM
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Would Ce2O3 have the same tendency to oxidize bromide ions to bromine as CeO2?
I am trying to plan how to go about producing CeBr3 and LaBr3. The lanthanum seems straight forward enough with the ammonium bromide route but I am
having trouble finding viable techniques for producing the cerium tribromide.
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woelen
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Ce2O3 is not oxidizing. Cerium can exist in two oxidation states, +4 and +3. It is quite strongly oxidizing when in the +4 oxidation state, especilly,
when brought in (aqueous) solution.
Another issue might be the inertness of CeO2. This oxide, especially when heated for a longer time, becomes exceedingly unreactive and you will have
difficulty getting it converted to anything else. I know from experience that CeO2 only can be dissolved in hot concentrated H2SO4. Aqueous solutions
do not act on CeO2. But once the CeO2 is converted to a soluble compound, such as Ce(SO4)2, then you have a very reactive oxidizing agent.
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unionised
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Have a look here
http://www.sciencemadness.org/talk/viewthread.php?tid=156107
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Boffis
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No, Ce2O3 should be OK but preparing this oxide and preventing from oxidizing to CeO2, which it does very readily may not be so easy. Could you use a
proxy such as cerium III oxalate?
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LRM
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Quote: Originally posted by Boffis  | | No, Ce2O3 should be OK but preparing this oxide and preventing from oxidizing to CeO2, which it does very readily may not be so easy.
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Definitely not looking forward to producing Ce2O3 but the whole process I am looking at would need to be done mostly in a dry inert atmosphere anyway.
If I do have to go the Ce2O3 route I was thinking that going straight from a tube furnace to the ammonium bromide reaction for the CeBr3 might work
out with only minimal losses to oxidation during the tube to tube transfer.
I was also looking into a couple other cerium compounds but separating the CeBr3 from the side products without putting everything into solution does
not seem likely.
The last step of my project will require the CeBr3 to be anhydrous so the ammonium bromide route with an oxide is very attractive. Would be great if I
am overlooking some easier option here!
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