Sciencemadness Discussion Board - RFNA > Is it good for anything?

RFNA > Is it good for anything?

freedompyro - 27-1-2012 at 00:32

RFNA has proved to be nothing but a pain in the neck. Half of the common nitrations will NOX at temperatures of even 15c during additions... You need either a perfect mask or a additional fan sucking the air away from you. A couple people I know note much lower yields with RFNA with the nitration of the common liquid nitric esters than with WFNA.

What really has me scratching my head is this. A nitration was done where EG was dissolved into HNO3, then H2SO4 was slowly added maintaining a temperature of exactly 15-18C. The nitration would NOX from the addition of H2SO4.

This was overnight FROZEN H2SO4. It's impossible there was any hotspots... Nitration via dissolving of a substance into HNO3 and precipitating it by the dripping of frozen H2SO4 with stirring is the safest way to do nitrations in my opinion. Provided you don't let the reaction drop below 15C and prep yourself for a later runaway.

Sigh... Time to break out the double boiler setup to get the HNO3 heated up to 45-50C. A air compressor will run air through a Aluminum tube into the bottom slowly.

A friend of mine claims that in the conversion of RFNA to WFNA the NOX will use water and that if you can't get it to clear up fully you need to add tiny amounts of urea. That reaction will also release water that is needed for the bubbler if it is all used up.

I'm not too sure about that... What reaction is occurring when you bubble oxygen through RFNA?

[Edited on 27-1-2012 by freedompyro]

Ral123 - 27-1-2012 at 02:21

By mixing EG with RFNA aren't you making the perfect conditions for the perfect runaway(that brings your house down

)? And then add H2SO4... I have some yellow acid that yields good amounts of hexogen and it gives off quite a lot of NO2. At the end of the reaction its clear btw.

AndersHoveland - 27-1-2012 at 03:39

The presence of nitrogen dioxide will lead to undesirable oxidation in many types of nitration reactions. But there are some types of nitrations where nitrogen dioxide is not undesirable, and there are a few types of nitrations can be done with nitrogen dioxide instead of nitric acid.

Red fuming nitric acid is ideal for making trinitromethane, for example.

But for nitramines (t.ex. RDX) or nitrate esters (t.ex. nitroglycerin), red fuming nitric acid cannot be used.

Here are some of the reactions where red fuming nitric acid could be useful,

Quote:

Chlorofluoronitroacetic acid reacts with red fuming nitric acid (HNO3 / NO2) to give chlorofluoronitronitrosomethane,

Quote:

ethylnitrolic acid (1-Nitro-1-oximinoethane)
CH3C(NOH)NO2
"was prepared by mixing acetone with nitric acid (of 24% concentration) and a little fuming HNO3 and allowing the mixture to stand for 8 days at room temperature. An ether extraction gave on evaporation some acetylmethylnitrolic acid
Beil 3,621 and R. Behrend & H. Tryller, Ann283,221- 3( 1894)

"... right after the strong oxidation left behind was a clear, thick yellow oil of a pungent odor. According to Jahresbericht über Fortschritte der Chemie (1902), Behrend and Tryller, p. 1075-77 this oil contained one-third to half acetylmethylnitrolic acid (CH3.CO.C(NOH).NO2) (cryst., mp. 62 deg., very decomposable) and other byproducts, including pyruvic and oxalic acids. They say in the same instance methyethyl ketone affords CH3COOH, HCOOH, and considerable amounts of ethylnitrolic acid and dinitroethane"

Ideally, if you had an ozone generator, you could bubble ozone into the RFNA, oxidizing the NO2 into nitric acid, and further absorbing more of the water.
(2)NO2 + (2)O3 + H2O --> (2)HNO3 + (2)O2

[Edited on 27-1-2012 by AndersHoveland]

Pulverulescent - 27-1-2012 at 05:23

Quote:

I'm not too sure about that... What reaction is occurring when you bubble oxygen through RFNA?

Dry O2 slowly oxidises NO2 to the negative nitrate ion ─ this then forms the anhydride N2O5 with NO2+!
The reaction is slow at low temperature but heating the solution drives off some NO2 which is some small loss!

P

AndersHoveland - 27-1-2012 at 05:41

Would one be paranoid to suspect that Pulverulescent wishes to make satire of my posts?

Dry O2 does not react with NO2 in the absence of water. And bubbling NO2 and O2 into concentrated nitric acid will not be absorbed beyond a certain concentration. I am not sure exactly what this is, but I think it was somewhere between 72 to 83 percent (by weight).

thread discussing making nitric acid from NO2,
http://www.sciencemadness.org/talk/viewthread.php?tid=13749&...

articles mentioning reaction of NO2 with O3,
http://pubs.acs.org/doi/abs/10.1021/j100907a003
http://www.atmos-chem-phys.net/11/4929/2011/acp-11-4929-2011...

[Edited on 27-1-2012 by AndersHoveland]

woelen - 27-1-2012 at 07:06

The reaction between O2 and NO2 requires the presence of free water molecules. I do not believe any N2O5 can be formed, only in the presence of water, HNO3 will be formed. But if the concentration of water becomes too low, then the reaction does not occur or only occurs slowly and NO2 simply remains dissolved and O2 bubbles through.

If you only have water and NO2, then you get HNO3 and NO. When oxygen is present as well, then the NO reacts with O2 to give NO2 and this can react with more water to make more HNO3. So, the net effect is reaction of NO2, O2 and water to HNO3. IIRC this works well for concentrations up to appr. 70% HNO3. Above that concentration the reaction becomes slower and free NO2 can remain dissolved in the acid without reaction. Acid of 70% concentration can be slightly yellow, acid of 90% HNO3 can be deep yellow (like piss).

Pulverulescent - 27-1-2012 at 07:42

Quote:

Would one be paranoid to suspect that Pulverulescent wishes to make satire of my posts?

OK, if one were to consider the simple fact that I hadn't even read your post, in the first place, well then yes, that would likely be paranoia!
All I saw was someone wishing to have the reaction explained!
When we talk of RFNA, we're talking about what comes over into the receiver and you know as well as I that this isn't exactly anhydrous RFNA!
The anhydride formed dissolves in and reacts with the small quantity of water that comes over with the acid.
If, when the water is consumed, some NO2 remains, urea will decompose the remaining HNO2, reintroducing water to the acid!
And besides, HNO2 is not stable.
Prolonged gentle agitation by bubbling air or oxygen will eventually decolourise the acid, but this takes just too fucking long . . .

P

VladimirLem - 27-1-2012 at 07:52

Wahaha...if this board would be 4chan i would say: OP IS A FAGGOT

seriously, RFNA is awsome^^...at PETN i got extreme high yields (~2.3from1g PE), MHN is good (~1.9from1gM) and so on...whatever you made wrong, RFNA isnt the problem you looking for

Pulverulescent - 27-1-2012 at 08:00

─ And AH, just what was it exactly that made you suspect that what I said was, in any way, 'satirical'?

P

Pulverulescent - 27-1-2012 at 08:24

Quote:

Wahaha...if this board would be 4chan i would say: OP IS A FAGGOT

I've no real idea why you should make such a 'comment', Vlad the Impaler, but my experience is that that people who are most rabidly homophobic are, in fact, people who are trying that little bit too hard to cover up their own homosexual leanings . . .
If I were gay, I'd be (straight

) up-front about it, and not give a shite what the great 'unwashed' thought!

P

quicksilver - 27-1-2012 at 09:17

It's so easy to clean up RFNA with a bit of urea and some bubbled aeration I would say if your percentage is high; it's worth your time to work with it. Try one gram per 250ml and a common air bubblier (aquarium pump is fine) under the hood. This does not need to be a protracted period of time. give it twenty minutes to half hour. You should see some clarity. If all you have is tech-grade prills of urea, at minimum, crush them; better, recrystallize / purify the urea. Do not use any urea that is fertilizer-level contaminated with rust from prill-tower....that MUST be cleaned up.

VladimirLem - 27-1-2012 at 11:28

Quote: Originally posted by Pulverulescent

Quote:

Wahaha...if this board would be 4chan i would say: OP IS A FAGGOT

) up-front about it, and not give a shite what the great 'unwashed' thought!

P

...that was just a joke, nothing more - if you know 4chan, you would get it, but doesnt matter...finaly i know that i am gay, cause you said it...

:/

freedompyro - 27-1-2012 at 12:03

I have technical grade urea.

Quote: Originally posted by Ral123

By mixing EG with RFNA aren't you making the perfect conditions for the perfect runaway(that brings your house down

)? And then add H2SO4... I have some yellow acid that yields good amounts of hexogen and it gives off quite a lot of NO2. At the end of the reaction its clear btw.

Re> Ral123 - Dissolving EG, NG, and PG into nitric acid then precipitating it by a slow steady addition of H2SO4 works very smoothly, however... You must maintain a temperature of above 15C in order to keep the reaction going so you don't get a sudden runaway later. In my experience around 17C is a good level.

This method of nitration I wouldn't recommend for beginners.

[Edited on 27-1-2012 by freedompyro]

AndersHoveland - 27-1-2012 at 14:20

Quote: Originally posted by woelen

If you only have water and NO2, then you get HNO3 and NO.

I believe this may be a misconception. There seems to be an equilibrium.

In water, nitrogen dioxide dissacociates into nitric and nitrous acids. Nitrous acid can disassociate into nitrogen dioxide and nitric oxide.

2 NO2 + H2O <==> HNO3 + HNO2

2 HNO2 <==> H2O + NO2 + NO

Bubbling nitric oxide into dilute nitric acid was able to decompose ammonium perchlorate, whereas there was no decomposition when nitric oxide was used alone.

Quote:

...gas phase reaction between nitric acid and nitric oxide to form nitrogen dioxide and water

2 HONO2 + NO --> H2O + 3 NO2

"Gas Phase Reaction of nitric oxide with nitric acid", I. R. McKinnon, J. G. Mathieson, (1978) Australia

http://pubs.acs.org/doi/abs/10.1021/j100470a003

The literature is conflicting on the stability of pure nitric oxide gas. This older paper claims there was no noticeable change after 40 years, http://pubs.acs.org/doi/abs/10.1021/j150561a030

Quote:

cryogenic distillation of liquid NO...
In liquid form, nitric oxide (NO) is an unpredictable, highly shock-sensitive, explosive. It is comparable to nitroglycerin.

Nitric oxide boils it -152 C and freezes at -163 C.

Michael Fox (obtained Doctoral Degree in Physical Chemistry at University of Hawaii)

http://www.chemaxx.com/nitric_oxide_explosion2.htm

It is difficult to find any solid information about the stability of nitric oxide, or possible half-life, because the internet searches are cluttered with the compounds biological effects.

[Edited on 27-1-2012 by AndersHoveland]

Microtek - 27-1-2012 at 14:24

I think that method of nitration is generally asking for trouble, at least if you are suggesting that the substrate (EG, PE, or whatever) is dissolved in aqueous nitric acid (common 60-70 %), and that sulfuric acid is then added to this.

Anyway, to decolorize RFNA just heat it to 50 C while bubbling dry air through it. Ambient air will not suffice, it must be dried by being led through some dessicant (I prefer CaCl2 scale) or you will dilute the nitric. You will also dilute it by adding urea, so if you need anhydrous acid (not necessary for the things it seems you are making) that is no good.

woelen - 28-1-2012 at 09:28

Quote:

Bubbling nitric oxide into dilute nitric acid was able to decompose ammonium perchlorate, whereas there was no decomposition when nitric oxide was used alone.

If this reaction occurs, then it will be a VERY slow one. Especially when dilute solutions are used, I simply expect the NO to bubble through the liquid and hardly expect any reaction with HNO3 to NO2. In strongly concentrated acid I can imagine that this reaction occurs (HNO3 then is non-ionic), but in dilute solutions, HNO3 hardly exists, only H(+) and NO3(-) are in solution and the NO3(-) ion certainly does not react with NO. So, if someone is claiming decomposition of ammonium perchlorate under the given conditions, then at most trace amounts were decomposed.

AndersHoveland - 12-2-2012 at 22:11

Quote: Originally posted by woelen

If this reaction occurs, then it will be a VERY slow one. Especially when dilute solutions are used

Dilute nitric acid (>5%) is typically a very poor oxidizer, it failed to oxidize copper foil after several days. This is no doubt because nitric acid in dilute solution is almost entirely in the form of the nitrate ion, which is relatively inert.

Nitric oxide, however is a reactive reducing agent. Probably because it behaves as a radical.

Another mechanism through which the nitrate could potentially transfer away one of its oxygen atoms through intermolecular resonance with the nitric oxide. This type of process is spontaneous and happens at room temperature. Benzofuroxans, for example, are known to tautomerise in this manner, and nitrobenzofuroxans spontaneously tautomerise in another surprisingly flexible way. (see "scheme 17" on page 16 in the link)
http://www.ark.chem.ufl.edu/Published_Papers/PDF/256.pdf
4-methyl,3-nitro-benzofuroxan is thus actually the same compound as 6-methyl,3-nitro-benzofuroxan, although they are considered different structural isomers.

I strongly believe the reaction would be very rapid, which would be interesting because dilute nitric acid is otherwise not easily reduced.

Another related experiment I have done:
http://www.sciencemadness.org/talk/viewthread.php?tid=18331

[Edited on 13-2-2012 by AndersHoveland]

Fantasma4500 - 25-8-2014 at 23:23

[/rquote]

Dilute nitric acid (>5%) is typically a very poor oxidizer, it failed to oxidize copper foil after several days.[/rquote]

a-actually... benzyl alcohol with HNO3 and abit of NaNO2 as catalyst gives decent amounts of benzaldehyde, one time it went abit past 5% and i managed to get a runoff, patents i read on it stated about 5-10% nitrate formed, which is really not bad at all

also back to topic: you can make some neatly powerful nitrocellulose if you first nitrate with standard nitration acid mix, then with RFNA
https://www.youtube.com/watch?v=RJnZrZOq8wA

thought RDX required WFNA, however.. been wondering abit myself about the specific uses of RFNA, i may soon try to add some aluminium to some RFNA to see if my idea with Al reacting with the NO2 giving aluminium nitrate (nitrite?) and clear high conc. HNO3 may work

hyfalcon - 26-8-2014 at 03:37

Aluminum will passivate. I use nitric to clean my aluminum concrete molds. It loosens the concrete where it can be pressure washed off but it doesn't eat the mold up in the process.

Fantasma4500 - 26-8-2014 at 08:17

but.. normally HNO3 isnt contaminated with NO2.. i mean.. practically if HNO3 passivates Al totally, you should be able to use full upper destillation part of aluminium, but it will slowly get eaten away by the NO2, however rather slowly

Bert - 26-8-2014 at 20:37

Inhibited Red Fuming Nitric Acid

About .5% Hydrogen fluoride (or several other things!), protects your metal components...

Goes down nicely with a bit of the good ol' UDMH

[Edited on 27-8-2014 by Bert]

Fantasma4500 - 30-8-2014 at 06:36

against all expectations aluminium was incapable of removing the discolouration of the RFNA

anyhow wouldnt a decent slurry with HDN and RFNA be somewhat strong?
it should give a mix of HDN, HMX, RDX and all of those other more or less complex compounds made when making RDX, im thinking it may be somewhat around the same as AN with H2SO4 and then NM mixed in, in which Axt found to have pretty great properties overall

anyhow, as of what i found out with Al, seemingly that it doesnt react --- wouldnt that make Al with HNO3 a potential explosive, although its said that Al first reacts in the gas cloud..?

papaya - 30-8-2014 at 08:43

I'm sorry for speculation, but wouldn't addition of NH4NO3 into RFNA turn it colorless due to NO2 reduction by NH4+ ions ? If that works, I don't think any remaining NH4NO3 is going to interfere with most nitration reactions (for what else you need HNO3?)

NeonPulse - 30-8-2014 at 15:24

I'm not too sure what happened but I did a PETN batch a while ago using a yellowish colored HNO3 and my yield didn't seem to suffer at all.low yields are a.problem with RFNA I thought. From 100mls acid and 33g Pentaerythritol I got around 81g of product. Not bad I think. At first I thought it wasn't fully dry but after extending the drying period to 3days it was unchanged. I did get a small cloud of NO2 that was persistent at around the 16℃ mark though but no sign of a runaway. Anyway i did make a video of the process of cleaning RFNA toWFNA and stuck it on YouTube called Clearing NO2 from RFNA. It pretty much explains how to do it. Ill post the actual link later. I think RFNA is only good to clean into WFNA. it is so much more useful that way and less problems will arise during nitrations.

markx - 31-8-2014 at 11:38

Quote: Originally posted by NeonPulse

I'm not too sure what happened but I did a PETN batch a while ago using a yellowish colored HNO3 and my yield didn't seem to suffer at all.low yields are a.problem with RFNA I thought. From 100mls acid and 33g Pentaerythritol I got around 81g of product. Not bad I think. At first I thought it wasn't fully dry but after extending the drying period to 3days it was unchanged. I did get a small cloud of NO2 that was persistent at around the 16℃ mark though but no sign of a runaway. Anyway i did make a video of the process of cleaning RFNA toWFNA and stuck it on YouTube called Clearing NO2 from RFNA. It pretty much explains how to do it. Ill post the actual link later. I think RFNA is only good to clean into WFNA. it is so much more useful that way and less problems will arise during nitrations.

RFNA can be quite deceptive as far as coloration goes....slight contamination and full saturation by dissolved NO2 look rather similar judged by eye. I had a really bad batch of RFNA that had been standing in a clear flask outside on the balcony corner in the direct rage of sunlight for about a year. The coloration of the acid was just a bit more to the red side than a freshly distilled batch, but the amount of dissolved NO2 was humongous. I managed to clear it up by redistillation. The NO2 saturated part comes over as heads and can be separated from the clear fraction of WFNA. Then the red part can be cured by addition of urea and returned to the distillation apparatus, repeating the cycle as many times as needed. I managed to recover about 80% of the bad batch as clear WFNA after 3 cycles through the distillation apparatus. For sure it is more trouble than just urea addition and aeration, but it is quicker and concentration can be preserved at maximum. With a really bad batch like the one I had it probably is the only way...

roXefeller - 31-8-2014 at 13:42

The video from NeonPulse. I'm guessing that you were keeping it in a warm bath during the evolution. Its a good looking video.