Sciencemadness Discussion Board - Ceric ammonium nitrate- uses and synthesis

Ceric ammonium nitrate- uses and synthesis

garage chemist - 19-11-2007 at 21:49

The Ce(IV) ion is a powerful oxidiser in aqueous solution, stronger than chlorine, and capable of very interesting reactions, especially in organic chemistry.
When its oxidising properties are to be used in preparations, it is most commonly employed as the salt ceric ammonium nitrate, or short CAN: (NH4)2Ce(NO3)6
I think that this reagent has received much less attention among amateur chemists than it deserves.

The Organikum (22nd edition) has a preparation of p-tolualdehyde (p-methylbenzaldehyde) from p-xylene by oxidation of one of the methyl groups to the aldehyde group with CAN.
A yield of 68% is claimed, which is very good for such an aldehyde preparation that easily can result in overoxidation to the acid when other oxidisers are used.

This preparation is very simple and straightforward: 0,4 mol CAN in 200ml 50% aqueous acetic acid is heated with 0,1 mol p-xylene on the boiling water bath under strong stirring and reflux for 20 min (soln becomes light yellow). After cooling down it is extracted thrice with ether, the pooled extracts washed with Na2CO3 soln to remove acidic byproducts, dried with MgSO4 and distilled to separate solvent, product, and impurities.

I think this could work just as well for the oxidation of toluene to benzaldehyde. Isnt that something a lot of people here always want to do?

It also oxidises benzylic alcohols to the aldehyde, and phenols to quinones.
The wikipedia page on CAN is very informative:
http://en.wikipedia.org/wiki/Ammonium_cerium(IV)_nitrate

This useful chemical is, however, quite expensive (500g 109€ from Aldrich, cheapest grade) from most chemical suppliers, far more so than the other well-known oxidants like permanganate and dichromate.

A method for its preparation at home would be something worth investigating.
A cheap source for cerium compounds exists: ceric oxide, CeO2, is used for polishing gems and glass and is cheap in this form.
Be sure to get the white quality, this is essentially pure CeO2.
I will buy 200g of such CeO2 soon.

As its use for polishing suggests, this oxide is strongly calcined (so that it consists of hard, abrasive crytals) and thus unreactive, just like calcined alpha-Al2O3.
It does not dissolve in acids unless a reducing agent is present, according to Brauer, and then it goes in solution as the Ce(III) ion.
Wikipedia says that a solution of the Ce(NO3)6(2-) ion can be obtained by dissolving Ce2O3 in conc HNO3 (oxidation of the Ce(III) takes place)- this has to be boiled according to Brauer.
After evaporation of most of the HNO3, ammonium nitrate solution can be added to form the salt, and this crystallized after repeated evaporation with HNO3 (dont ask why, Brauer says it).

Brauer gives a rather tedious method for CeO2 dissolution using hydroquinone which gives problems because the benzoquinone byproduct must be gotten rid of before further processing. A different and less problematic reducing agent seems to be necessary- I'd like to try formic acid.

Brauer further gives a procedure for crystallizing the CAN and an ether extraction of ceric nitrate from CAN in 6N HNO3 for complete separation from other rare earth elements- not necessary for us if the starting material is pure.
We can stop after the crystallization of CAN from the HNO3 solution after addition of AN and repeated evaporation with HNO3.
Obviously the yield will be far from quantitative due to CANs high solubility (mother liquor can be further boiled down once to yield a second crop), but the Ce values can always be recycled from the mother liquors (and spent CAN during further use in synthesis) simply by diluting with water and adding oxalic acid while hot- the oxalates of the trivalent rare earths are all sparingly soluble, and the oxalic acid acts as the reducing agent as well.

If someone wants to do this, read the chapter "Pure cerium compounds" in Brauer, it essentially contains a preparation of CAN but not an optimal one.

When I receive my CeO2 I will try this out and report here.

Has anyone here done preparative work with Ce(IV) compounds or knows about them? Woelen?

Any comments or tips towards synthesis of CAN?

[Edited on 20-11-2007 by garage chemist]

Xenoid - 19-11-2007 at 22:15

Oh! No! Please don't use CAN as an abbreviation for this chemical!

CAN is the pretty much standard abbreviation for Calcium-Ammonium Nitrate, a fertilizer which is a blend of about 20% CaCO3 and 80% Ammonium Nitrate.

Wouldn't CeAN or CEAN be more appropriate!

Regards, Xenoid

not_important - 19-11-2007 at 22:28

Ethanol or H2O2 have been used as reducing agents when dissolving CeO2 in HCl or H2SO4, and also to reduce slightly acid solutions of Ce(IV).

Frederick Smith's Cerate Oxidimetry starts with a low grade of CeO2, 45% or 60% ceric oxide. These grades dissolve in HNO3, the 45% with evolution of heat. I suspect that these grades are no longer obtainable, or if so only in box car quantities.

I'll dig the pamphlet out and type in the CAN production from it.

CAN is nearly insoluble in concentrated HNO3, while the REE(III) nitrates are somewhat soluble. Thorium, as the nitrate, would be the main contaminate, these days thorium doesn't really show up in REE products.

woelen - 20-11-2007 at 00:48

I have not really done preparative work with cerium salts, but I have some experience with the cerium(III) and (IV) ions.

Cerium(III) is amazingly hard to get oxidized to cerium(IV). You need potent oxidizers (e.g. hot persulphate) in order to get it oxidized. Cerium(IV) oxide, CeO2, even the freshly precipitated oxide/hydroxide only very slowly dissolves in acids, giving a deep yellow solution.

I am afraid that the dissolving of calcined CeO2 will be VERY hard. CeO2 is fairly cheap though.

http://cgi.ebay.nl/CERIUM-OXIDE-Ce-99-8-250g-Very-high-quali...

I have good experience with this seller.

YT2095 - 20-11-2007 at 03:19

just a quick question, since quite a few of the rare earth metals share a similar chemistry, would it possible to use Samarium instead?

I have some of that, but the only Cerium I have is in the form of an alloy in Lighter flints.

yan123 - 20-11-2007 at 03:23

generally, CAN is considered as cerium ammonoum nitrate, Chemiscal reviews has a paper talk about CAN (cerium ammonoum nitrate) in 2007.

Quote:

Originally posted by Xenoid
Oh! No! Please don't use CAN as an abbreviation for this chemical!

CAN is the pretty much standard abbreviation for Calcium-Ammonium Nitrate, a fertilizer which is a blend of about 20% CaCO3 and 80% Ammonium Nitrate.

Wouldn't CeAN or CEAN be more appropriate!

Regards, Xenoid

garage chemist - 20-11-2007 at 04:50

Xenoid: I think we should always use the proper term in a thread at least once before we use the acronym. I also wouldnt like it if everyone were throwing around acronyms for chemicals that nobody but experts in a spceific field know about.
I always first explain the acronym (except in obvious cases, like THF or DMF), then I use it for the rest of the thread.
It should also mostly be obvious from the context what CAN would stand for- when people are talking about oxidation of methyl groups or alcohols with CAN, then one can be sure that it isnt a nitrate fertilizer they are talking about.

Quote:

CAN is nearly insoluble in concentrated HNO3, while the REE(III) nitrates are somewhat soluble. Thorium, as the nitrate, would be the main contaminate, these days thorium doesn't really show up in REE products.

Thats great to hear, that would be a huge advantage if it is true. But then why does Brauer talk about concentration of the mother liquor to get more crystals? Maybe the HNO3 isnt so concentrated at that stage of the procedure...
I'll have to see myself.
It would be really nice if you could post the article you were speaking of, but the white, pure CeO2 is the only grade that I can get. Nobody seems to use impure rare earth compounds any more.

Samarium does not occur in tetravalent form.
The lanthanides that can occur in tetravalent form are Ce and Tb, and to a very limited extent (dont really know what is meant by this- maybe very unstable?) Pr and Nd.
Of these, only Ce(IV) is metastable in water, the other ones all oxidise water to oxygen and therefore have no aqueous chemistry.

Ce is the most abundant rare earth metal, and by far the easiest one to obtain pure- oxidise it to Ce(IV) and adjust the pH so that hydrated CeO2 precipitates while all other lanthanides stay in solution. Or follow Brauers method with ether extraction of ceric nitrate.
Similar with Eu, which can be reduced to the divalent state and precipitated as the sulfate.
The other rare earths are more difficult to separate.

Eclectic - 20-11-2007 at 06:45

A cheap source of lower purity CeO2 is used as a glass polishing material. Mine is pink/salmon color. Try a shop that cuts and installs plate glass, or their suppliers. Boiling with SO2 solution in water helps SnO2 dissolve in acids, maybe it would have the same effect on CeO2?

not_important - 20-11-2007 at 08:16

Actually it is fairly easy to take Ce(III) to Ce(IV). Simply make a solution of a Ce(III) salt alkalike, and allow it access to air for awhile. The Ce(OH)3 originally formed will darken to a red-orange, then change to a yellow as increasing amounts if the cerium are oxidised to the 4+ state. To do it quickly, added H2O2 and then bring to a boil.

Praseodymium also goes into a higher oxidation state, but it forms mixed valence oxides and is difficult to get into any single pure state other than 3+. It may help with the dissolution of ceric oxide by shuttling between oxidation states, which helps do the same to cerium. However the physical state of the oxide is important too, the low grade oxides used in the older preparations were likely ignited at a fairly low temperature and intended as a source of the REE rather than as an end product like polishing powder.

I've had a range of difficulty in dissolving CeO2 from various sources. Some would go into solution in constant boiling HCl pretty nicely, others took prolonged treatment with acid and ethanol, one batch took long boiling with concentrated H2SO4. And one !@#$%^&*( bag wouldn't dissolve in any acid treatment, I ended up lining a large crucible with a cm or so of the oxide, then filling the center with a mix of the oxide and sodium carbonate, fusing the mix, and then dissolving that in HCl.

I'll try to get access to a scanner in the morning to get those couple of pages in.

DeAdFX - 20-11-2007 at 10:06

Would molten Ammonium nitrate + Cerium (IV) or (III) oxide be sufficient to form the double nitrate salt? I remember there was a discussion here about using metal carbonates or oxides and ammonium nitrate to produce the corresponding metallic nitrate?

YT2095 - 20-11-2007 at 10:07

Quote:

Originally posted by garage chemist
Samarium does not occur in tetravalent form.
The lanthanides that can occur in tetravalent form are Ce and Tb, and to a very limited extent (dont really know what is meant by this- maybe very unstable?) Pr and Nd.
Of these, only Ce(IV) is metastable in water, the other ones all oxidise water to oxygen and therefore have no aqueous chemistry.

Thank You

JohnWW - 20-11-2007 at 10:11

Probably the cleanest way to oxidize Ce(III) to Ce(IV) in solution would be by electrolysis. In the solid state, finely divided Ce2O3 oxidizes to CeO2 on heating in air.

Of the rare-earth metals that exhibit the +4 oxidation state, only Ce(IV) is stable enough to exist in solution, being highly complexed because of its charge. Apart from CeO2 and salts of oxy-anions, the only other compound of it is CeF4 (and possibly oxyfluorides). The only other rare earths that stably exhibit the +4 oxidation states are Pr, Tb, and possibly Nd, although only as the non-stoichiometric solid oxides, Pr6O11 and Tb4O7, obtained by pyrolysis in air of the soluble salts as which they are isolated by ion-exchange chromatography. They are reduced to the +3 state with evolution of oxygen if dissolved in acids. (It is not certain what the composition of the higher oxide of Nd is, or whether it has been characterized at all).

not_important - 20-11-2007 at 20:51

OK, attacked is the basic prep pages and the cover of the pamphlet I was referring to earlier. I skipped the electrolytic ones, they take platinum electrodes and are more for analytical grade.

There's a table in there that shows one run where they went for 3 crops of CAN, although the text doesn't mention concentrating the mother liquor. The first crop was 3/5 or more of the cerium, purity of the CAN was 99,4%. The second crop was less than 1/5 of the Ce with a purity of 98,8%, the third was smaller at 90% purity. So a second crop may be worth doing, but past that you may be better hitting it with base to recover Ce as the hydroxide.

Under alkaline conditions, H2O2 or air will oxidise Ce(III) to Ce(IV), the resulting Ce(OH)4 can be dissolved in acids to get the ceric salt. This is as clean as electrolysis, and doesn't take expensive electrodes.

Note that NaOCl bleach will precipitate Ce(OH)4 from a solution of a Ce(III) salt. The hydroxide would need to be washed clean of Na and Cl ions, although the dissolution in nitric acid will take care of the chloride and a trace of sodium isn't likely to be important in many applications.

Attachment: CAN.zip (579kB)
This file has been downloaded 1219 times

NADPH - 13-2-2010 at 14:46

I tried to make (NH4)2Ce(NO3)6 all the way from ferrocerium rod.
First I dissolved about one third of huge ferrocerium rod in HCl. Reaction was quite violent (lot more violent than Nd2Fe14B magnets with HCl) and huge amount of H2 gas and heat was liberated. Also there was strong unpleasant smell. So I decided to seal reaction flask with stopper conected to rubber tubing to lead the gas far away and out through window (cheap alternative to fume hood). I left reaction overnight and then most of ferrocerium was dissolved. Then I diluted reaction with distilled water and filtrated off all undissolved particles until solution was clear.
Next I purified Ce(III) by precipitating cerium (III) sulfate with concentrated solution of sodium bisulfate (of course sodium sulfate works as well but bisulfate was only thing I had at the moment). Greenish Fe(III) was left in solution but white Ce (III) sulfate precipitated. I filtrated cerium (III) sulfate and washed few times with boilig water. Dried it in oven @120˚C.
Then I converted all the Ce (III) sulfate to Ce (IV) hydroxide by mixing it with hot Na(OH) solution and adding H2O2 to oxidize Ce(III) to Ce(IV). Before adding H2O2 I cooled reaction in ice bath but anyway H2O2 reacted quite virgously and after I dropwise added few mililiters of H2O2 colour changed to yellow (fine emulsion of Ce (IV) hydroxide after shaking) but most Ce (III) hydroxide was still unreacted as yellowish white clumps. Since H2O2 is not cheap, I added bleach (5% NaClO) instead. After few minutes of virgous shaking all clumps transformed to fine yellow emulsion which slowly settled down. Left ir overnight, filtrated and washed 4 times with distilled water and 2 times with acetone. After drying I got few grams of fine yellow powder of Ce(OH)4 (hydrate?)

As it was quite expensive to make, first I tried to make ceric ammonium nitrate (CAN) in small scale. I weighted 0.5 grams of Ce(OH)4 (0.0024 mol) and converted it to CeO2 by heating in test tube with butane torch until no more water was evolved.

After heating I got 0.36 grams of CeO2 (0.0021 mol).

Next I heated stoichiometric amount of ~14M HNO3 (0.9 ml) and then added CeO2. It reacted virgously but lot of CeO2 remained undissolved.

I heated mixture and added more HNO3 dropwise (~0.5ml) until most of CeO2 dissolved.

As a result I got cherry red solution which I transferred to fresh tube to get rid of undissolved particles (after settling them down for few minutes). Then heated it and added stoichiometric amount of NH4NO3 (0.34 g).

Solutions colour changed from cherry red to orange and orange precipitate formed instantly.

As the colour is exactly as it should be (http://en.wikipedia.org/wiki/File:Ceric_ammonium_nitrate.jpg) I assume orange precipitate is pure (NH4)2Ce(NO3)6

Sorry for my English. I hope you can understand what I wrote.

Jor - 13-2-2010 at 14:59

Wow, very nice of it indeed CAN! This is a nice way to make this material, although it is not THAT expensive when you can buy it (about 1 euro per 6 grams). You are sure that all CeO2 dissolved?
But why did you heat the hydroxide to make the oxide? You had a good chance that the oxide would be unreactive, and hydroxides are generally more reactive.

NADPH - 13-2-2010 at 15:08

Almost all CeO2 dissolved. After heating only small pellet of dark brown material remained.
I was not sure if Ce(OH)4 was hydrated or not. An I thought that more CAN will precipitate out if I will get rid of as much water as possible. That is why I calcined my Ce(OH)4

[Edited on 13-2-2010 by NADPH]

bbartlog - 13-2-2010 at 16:09

Nice work! just to nitpick though -

Quote:

I purified Ce(III) by precipitating cerium (III) sulfate with concentrated solution of sodium bisulfate (of course sodium sulfate works as well

Sodium sulfate shouldn't work? If NaOH can convert Ce(SO4)2 to hydroxide then it wouldn't makes sense for Na2SO4 + Ce(Cl)3 to give you cerium sulfate. I think you need bisulfate or sulfuric acid...

NADPH - 13-2-2010 at 16:46

bbartlog
Why sodium sulfate shouldn't work? Cerium (III) sulfate is much less soluble than cerium (III) chloride. I think there shouldn't be huge difference if I use sulfate or bisulfate or sulfuric acid

bbartlog - 13-2-2010 at 21:50

Sodium sulfate shouldn't undergo metathesis reaction with cerium chloride. In the case of the bisulfate or sulfuric acid the cerium is displacing the hydrogen, but it doesn't seem that it should be able to displace sodium.

NADPH - 14-2-2010 at 02:08

a) NaHSO4 => Na(+) + HSO4(-) <=> Na(+) + H(+) + SO4(2-)
b) Na2SO4 => 2Na(+) + SO4(2-)
___________________

c) Ce(3+)(aq) + SO4(2-)(aq) => Ce2(SO4)3 (s)

I still don't think there will be any difference if I use different sources of SO4(2-) ions

so I will make some Na2SO4 and try to precipitate Ce2(SO4)3.
I am almost sure it will work

_________________
p.s.
sulfate works
I just dissolved some Ce(OH)4 in nitric acid

then reduced Ce (IV) to Ce (III)

and added sodium sulfate solution. White Ce (III) sulfate was formed.

________________________
p.p.s.
I just did slightly different experiment.
weighted stochiometric amounts of Ce(OH)4 (2 g) and NH4NO3 (1.34 g)

dissolved Ce(OH)4 in ~14M nitric acid. Reaction was exotermic with lot of heat an fizzing. Eventually clear orange liquid formed.

Meanwhile I dissolved NH4NO3 in hot water. Then added it to cerium solution.

then poured on small petri dish

and gently evaporated in oven @120C until solid crust of CAN was formed

when I tried to stir with glass rod, the crust absorbed all remaining liquid and turned in dry hydrate. (According to literature its chemical formula is (NH4)2Ce(NO3)6*xH2O; x=6-8)

As a result I got 4.4 g of CAN hydrate

[Edited on 14-2-2010 by NADPH]

The WiZard is In - 9-4-2010 at 16:21

Pradyot Patnaik
Handbook of Inorganic Chemicals **
McGraw-Hill
2002

Sez ..... electrolytic oxidation of cerous nitrate in nitric acid
to ceric nitrate, followed by the addition of ammonium
nitrate solution.... Or... dissolving cerium (II) oxide ,
CeO-H2O in con. nitric acid followed by treatment with
ammonium nitrate.

** The book was reminded and could have been had
inexpensively a few years ago.

Copenhagen - 22-6-2010 at 18:27

I performed an experiment where I tried to obtain Cerium( IV) Sulfate from crude Cerium(IV) Oxide.
Bottger, W. Newer Methods of Volumetric Analysis pg. 27-28

Trial 1

50 g of CeO2 (FW: 172.115 g/mol) were placed into a 600-mL beaker containing 50 mL of 36 N H2SO4 that was pre-heated to 120 C with magnetic stirring. Addition was slow - scoopfuls at a time using a plastic spatula. Slow addition seemed prudent due to violent bubbling of the sulfuric acid upon addition of the solid. The careful addition of CeO2 was completed after 1 hour. The solution was heated for an additional 2 hours at 120 C. It was allowed to cool at room temperature for 30 minutes after which time it was slowly added to a 3000-mL beaker containing 1800-mL of cold water temperature (3 C). The solution was allowed to settle for 2 days after which time the supernatant was drawn off in portions with a 50-mL Pipet and transferred into a 250-mL Erlenmeyer flask. The rest of the solution was stored away in the 3000-mL beaker to allow for further settling.

Trial 2

200 g of CeO2 (FW: 172.115 g/mol) were placed into a 600-mL beaker containing 200-mL of 36 N H2SO4 that was pre-heated to 120 C with magnetic stirring. Addition was slow - scoopfuls at a time using a plastic spatula. Slow addition seemed prudent due to violent bubbling of the sulfuric acid upon addition of the solid. The careful addition of CeO2 was completed after 82 minutes. The reaction was heated for an additional 2 hours at 120. After 2 hours it was removed from the heat source and allowed to cool at room temperature for 4 hours. The supernatant was drawn off in portions with a 50-mL pipet and stored in a separate container. The precipitate was allowed to dry in room air. The precipitate has the bright yellow color typical of Ce(SO4)2.

Attachment: VolumetricAnalysis.tif (64kB)
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The WiZard is In - 23-6-2010 at 06:04

Quote: Originally posted by garage chemist

The Ce(IV) ion is a powerful oxidiser in aqueous solution, stronger than chlorine, and capable of very interesting reactions, especially in organic chemistry.
When its oxidising properties are to be used in preparations, it is most commonly employed as the salt ceric ammonium nitrate, or short CAN: (NH4)2Ce(NO3)6
I think that this reagent has received.

Uses? Not in my life. I received 5-6 lbs as a gift years ago...

The only use I am aware of is the analysis of the nitrogen content
of azides. And for the destruction/disposal of azides.

Run it through Google.com/books

not_important - 23-6-2010 at 06:45

Lots of uses for CAN A test for alcohols, which form a red complex then oxidise away. In inorganic and organic quantitative analysis, as an oxidising titration reagent; less common now due to various instrumental analysis methods. It can cleave the carbon bond in glycols HO-C-C-OH similarly to lead tetraacetate. A good way to oxidise many aromatic compounds to quinones.

Its oxidation of alcohols, aromatic amines, and phenols, make it useful in TLC for visualising those compounds.

Attachment: ceric_ammonium_nitrate_in_modern_chemical_synthesis.pdf (748kB)
This file has been downloaded 1433 times

DJF90 - 23-6-2010 at 07:11

Its also used for selective mono-debenzylation of tertiary amines, and for a few oxidations aside what not_important mentions; formation of quinones rings a bell...

elementcollector1 - 3-6-2013 at 14:40

When CeAN melts, does it do so without hazards? (I'm thinking of detonation due to the 'ammonium nitrate' present, decomposition of the substance, toxic gases, etc.)
If it doesn't, given Wiki's listed MP of 108 C, this could be a viable route to cerium metal, through molten electrolysis or otherwise.

Lion850 - 24-2-2020 at 23:16

Today I made cerium ammonium nitrate. As it boiled down the solution was deep orange and I expected orange crystals. Once crystals started to form the color was lighter but still orange while wet. It must have been boiling off its water of hydration because as the beaker cooled the crystals became rock hard and changed color to a nice yellow. I suppose the color varies between orange and yellow depending on amount of included water?

70F07824-D534-4DB0-9042-EC091AD8EF2F.jpeg - 2.2MB

Texium - 25-2-2020 at 07:10

CAN is never yellow like that. Anhydrous CAN is a deep red-orange. The only reference to a hydrated species that I could find was the mention of a (NH₄)₂[Ce(NO₂)₅(H₂O)₂]•2H₂O on Wikipedia, but its appearance is not described, and since it contains water ligands and one fewer nitrate ligand, it’s a fundamentally different compound, and probably doesn’t exhibit the same useful properties as CAN. Other Ce(IV) compounds are yellow though. You may have overheated it and produced basic cerium(IV) nitrate. Try redissolving the yellow stuff in nitric acid and adding more ammonium nitrate.

[Edited on 2-26-2020 by Texium (zts16)]

Lion850 - 26-2-2020 at 21:05

Hi Texium - quite a few places online mention the color as yellow to orange, and a picture search shows samples with similar yellow color. Mine was still orange when a wet paste, and only turned yellow when it reabsorbed the water as it cooled.

I’ll try a second batch when I have more reagents ready, and dry it in the desiccator from when it is a deep orange solution.

AJKOER - 27-2-2020 at 06:43

Some interesting comments at this ScienceDirect source (see https://www.sciencedirect.com/topics/chemistry/cerium ):

Some extracts:

"An easy and low-cost method, widely used for the obtention of aqueous suspensions of CeO2NPs, consists of the precipitation of cerium salts at basic pH. Briefly, oxidation of the Ce3 + ions from Ce(NO3)3 salt at basic pH conditions to the insoluble species Ce4 + using hexamethylenetetramine (HMT). During precipitation, CeO2 nanocrystals are formed and can further stabilize in aqueous medium with the same reagent HMT, that form the double electrical layer to prevent agglomeration [64]. Other basic reagents usually employed are urea, NH4OH and TMAOH [65]."

And:

"Further applications of the element include its use in zinc-cerium redox flow batteries [34]. These batteries function based on the generation of electricity in the presence of Ce4+ during the charge phase, or reduction reactions through the oxidation of zinc, which produces about 2.43 V [35]. A major component of these batteries is the electrolyte (i.e., methanesulfonic acid), which easily dissolves cerium compounds [36]. Ce4+ is produced through electrical driving forces that are used in the electrosynthesis of naphthoquinone [37]."

[Edited on 27-2-2020 by AJKOER]

Texium - 27-2-2020 at 12:14

Quote: Originally posted by AJKOER

Some interesting comments at this ScienceDirect source (see https://www.sciencedirect.com/topics/chemistry/cerium ):

Some extracts:

"An easy and low-cost method, widely used for the obtention of aqueous suspensions of CeO2NPs, consists of the precipitation of cerium salts at basic pH. Briefly, oxidation of the Ce3 + ions from Ce(NO3)3 salt at basic pH conditions to the insoluble species Ce4 + using hexamethylenetetramine (HMT). During precipitation, CeO2 nanocrystals are formed and can further stabilize in aqueous medium with the same reagent HMT, that form the double electrical layer to prevent agglomeration [64]. Other basic reagents usually employed are urea, NH4OH and TMAOH [65]."

And:

"Further applications of the element include its use in zinc-cerium redox flow batteries [34]. These batteries function based on the generation of electricity in the presence of Ce4+ during the charge phase, or reduction reactions through the oxidation of zinc, which produces about 2.43 V [35]. A major component of these batteries is the electrolyte (i.e., methanesulfonic acid), which easily dissolves cerium compounds [36]. Ce4+ is produced through electrical driving forces that are used in the electrosynthesis of naphthoquinone [37]."

[Edited on 27-2-2020 by AJKOER]

Please explain how this is the least bit relevant to this thread.

Lion850 - 28-2-2020 at 00:18

I made another batch which I reduced in volume on a steam bath and then when it was a wet pale orange paste the desiccator under vacuum. Again, the color lightened as it dried but it did end up a bit more orangy. See photo comparing the two batches.

This site mentions that the tetrahydrate is white.
https://www.americanelements.com/cerium-iii-ammonium-nitrate...

C815B6EA-B331-4B4E-BB64-941DAD1F8F34.jpeg - 1.8MB

woelen - 28-2-2020 at 04:22

Keep in mind that cerium exists in two oxidation states. Cerium(III) is colorless, cerium(IV) is yellow/orange. Cerium(III) salts hence will be white.

Texium - 28-2-2020 at 07:41

Yeah at best here you probably have a mixture of Ce(IV) and Ce(III). Could you please post the exact procedure that you used to make this, since your product looks so different than what others posted upthread?

Lion850 - 28-2-2020 at 18:41

Woelen, Texium:
I had available Ammonium Carbonate, Cerium (iii) nitrate, and 70% nitric acid. All LR grade. The ammonium carbonate and cerium (iii) nitrate are both while/clear crystals. I used this equation:
1Ce(NO3)4.6H2O + 2NH4NO3 = 1(NH4)2Ce(NO3)6 + 6H20
My app does not accept Ce(NO3)3 as input which was a problem. I decided to use the same quantities as nitic acid would be in excess and I hope the nitric acid would kick the cerium (iii) to cerium (iv).
I made ammonium nitrate by reacting 29g of the ammonium carbonate (which have the formula on the bottle as NH4HCO3.NH2COONH4, I assume this is to keep it stable) with 50g 70% HNO3.
NH4HCO3NH2COONH4 + 3 HNO3 = 3 NH4NO3 + 2 CO2 + H2O
This should have given me 44g ammonium nitrate in solution.
One fitth of the ammonium nitrate solution was poured off, should have been just over 8g in solution. 15g of cerium (iii) nitrate was added and stirred. The solution remained white with suspended cerium nitrate. Slight heat resulted in a clear solution.
5ml 70% HNO3 was added which turned the solution yellow with a hint of orange. This was boiled down and as the volume decreased it became more orange until at small volume it was a dark orange. At this point the color looked perfect!
When crystals started to appear the color became lighter and towards yellow. It was removed from the hot plate still wet with a bit of orange but as it cooled it absorbed the remaining moisture, became rock hard, and the last orange disappeared.

The second lot was basically the same but it was not dried on a hotplate. It was concentrated on a steam bath and then dried in the desiccator under vacuum overnight. Slightly darker product.

It will be great if you guys can recheck my amounts used, if incorrect I must learn

woelen - 1-3-2020 at 23:50

You should not rely on an app

If you have Ce(NO3)3, then you should not use Ce(NO3)4 in your equations. I once tried oxidizing Ce(NO3)3 to cerium(IV) with nitric acid, but this does not work very well. My solution did not get the deep yellow color I expected. Cerium(III) is fairly difficult to oxidize to cerium(IV). If you have peroxodisulfate (e.g. the ammonium salt or sodium salt), then you should be capable of oxidizing it completely to cerium(IV).

Lion850 - 3-3-2020 at 17:52

Hi Woelen:
I have potassium persulfate K2S2O8 is this the same as you mention above when you say peroxodisulfate? If one uses such a potassium or sodium salt my concern will be how to get this out of the mixture again?
Thanks.

woelen - 3-3-2020 at 23:31

Yes, "persulfate" is a somewhat incorrect name, frequently used for peroxodisulfate, S2O8(2-). There, also is another ion, SO5(2-), peroxosulfate, which also sometimes is called "persulfate". For your purpose the S2O8(2-) ion is better, it is a stronger (albeit slower acting) oxidizer.

I inderstand your reluctance in using this, you indeed have to get rid of the additional ions, brought into the solution, but if you don't use a good oxidizer, then I am afraid that you won't get cerium(IV) of good purity. Cerium(IV) itself is a strong oxidizer and to get this, you need an even stronger oxidizer. S2O8(2-) is one hell of an oxidizer, with a redox potential of just over 2 volts for its reaction to sulfate ion, independent of pH. Even permanganate does not accomplish that. This ion is capable of oxidizing Ag(+) to Ag(3+) and can oxidize Mn to its +7 oxidation state.