Concentrating HNO3 by decomposing HNO3 - Archive File

[megalomania]

HMTD Factory
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posted 03-06-2001 03:57 AM
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I guess explosive raw material can be discussed here.
Some idea came up this evening :

1.HNO3 can be made with water and NO2
2.HNO3 will decompose into NO2 in contact with formaldehyde
3. What if a drop of formaldehyde drips into 60%HNO3, fumes NO2, which then bubbles into
another bottle of 60%HNO3?

The decomposed HNO3 is sacrificed, given out
NO2, which concentrated another bottle of HNO3. Excess gas that is not absorbed fast enough can go into another bottle. Bottles can be cool bathed for better absorbtion.

In industrial process, NO2 bubbled through low conc. HNO3 can lift the concentration to, say, higher than 98%.

Damn I should have found out this when I had
access to some nitric acid.



green beret
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posted 03-06-2001 05:43 AM
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I also would like to hear any methods of concentrating nitric acid.


Morrigan
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posted 03-06-2001 09:52 AM
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If this works than that would be great. It would mean that no sulfuric acid has to be wasted. This can be used in the nitration instead. And since you don’t loose a lot of actual HNO3 it would almost be too good to be true. Anybody knows or this works?


Mr Cool
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posted 03-06-2001 02:46 PM
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4NO2 + O2 + 2H2O -> 4HNO3
Therefore oxygen will also be needed. The above reaction is how HNO3 is made industrially. I think this is a pretty good idea, but surely some of the original HNO3 will react with the formaldehyde, releasing NO2 as a product, like when copper reacts with conc. HNO3?

If we could find a way to break it down with catalysts, or maybe you could heat it to break it down without boiling off any water and diluting the HNO3 in the second flask, then that would be better.



HMTD Factory
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posted 03-06-2001 04:38 PM
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Actually oxygen is not involved. When NO2 reacts with water it will produce HNO3 and HNO2. HNO2 can self react to produce HNO3 and some byproduct(NO and some water).
Beware that when HNO3 is reduced to low concentration, copper will not produce NO2 anymore but will produce NO instead. Formaldehyde itself is a catalyst.

2NO2 + H2O -> HNO3 + HNO2(absorbtion)
3HNO2 -> HNO3 + 2NO + H2O(self react of HNO2)
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net :

3NO2 + H2O -> 2HNO3 + NO

The first flask will be filled with 60% HNO3 and a drip of formalin. it will fume out NO2
in large quantity. Gas is guided into a second flask of HNO3, excess gas not absorbed goes to the third flask of HNO3, excess gas goes to the fourth...etc.

When the second flask is concentrated, it can be removed for use. The original third flask
will be the second, fourth become third, a new flask of raw HNO3 will be the fourth...

The process will be encouraged under low temperature and high pressure. The first flask will experience the highest pressure, the second will be the second highest, third the third, foruth the foruth. (due to the liquid pressure need to be overcame in each flask.)

Using NO2 to concentrate HNO3 is a process not used widely in industry because boiling HNO3 and H2SO4 is cheaper.

Another way to concentrate HNO3 involving H2SO4 is to make weak HNO3 into a salt say
NaNO3. The salt then react with H2SO4 to produce HNO3, which can be distilled out to seperate with Na2SO4 and remaining H2SO4.



Mr Cool
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posted 03-07-2001 04:52 PM
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Oxygen makes it much more efficient, because it will oxidise the NO produced, turning it into NO2, which will dissolve and make more HNO3. That is why it is used in large scale production.
Using NO2 is not used to concentrate HNO3, it is used to make it in the first place, because it is a great deal cheaper on an industrial scale than using H2SO4 and a nitrate.
So the formaldehyde isn't used up at all? That's good.


HMTD Factory
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posted 03-08-2001 03:54 AM
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I know it is used to produce HNO3 but in the previous context NO2 is used to "lift the concentration" of HNO3 so we can call it "concentrating".


Mr Cool
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posted 03-08-2001 04:07 PM
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Yeah I know what you mean.
I still say adding O2 as well is a good idea.


PHILOU Zrealone
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posted 03-09-2001 09:01 AM
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Heh guys, enough dreams or talk about nothing... let us think a bit:
HNO3 with NO2 should give conc. HNO3 following what you all say!!!!Bullseyesshit
Then enlight my stupid constatations with your big knowledge:
*why the process to make HNO3 from NO/NO2/H2O/O2 can only reach low conc. HNO3 (5%) and that it needs to be distilled to get the 69% HNO3??????
*If NO2 with HNO3 would turn into conc. HNO3 spontaneously; then why the hell are we so concerned by a little NO2 in our HNO3 when making let's say PETN, NG, RDX,...red HNO3 should not exist then and thus shouldn't be a problem to us!!!!
Let's hope you got the point!

Think twice before dreaming or affirming things!!!!


------------------
"Life that deadly disease sexually transmitted".
"Chemistry is all what stinks and explode; Physic is all what never works! ;-p :-) :o)"



HMTD Factory
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posted 03-10-2001 01:41 AM
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Because the dissloving of NO2 in water is a reversable process. If the environment favors on direction, the balance will shift. Sometimes the shift is so insignificant it is
too slow for mass production.
One reason that in industry HNO3 is only made to 70% is that "They can't afford to wait that long" to use one single process. concentrating HNO3 with H2SO4 (stage 2) will be more cost effective than blowing NO2 into it.

I hope you got the point.



Mr Cool
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posted 03-10-2001 08:15 AM
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It does not need to be distilled if the conditions are correct. If it needed to be distilled from 5% in industrial processes, this reaction would not be used because it would be too costly. But it is used, so distillation is unecessary.
NO2 with HNO3 will not turn into conc. HNO3. None of us have said that it will. It needs water and oxygen, and conditions that favour a reaction.
Like HMTD said, I hope you get the point.
I thought you were better than that.

Edit: this is why HNO3 below a certain conc. is always colourless, not red or brown. The dissolved NO2 will gradually react with the water in it and O2 from the air to make HNO3. However, high conc. HNO3 does not contain enough water to react all of the NO2.

[This message has been edited by Mr Cool (edited March 11, 2001).]



firebreether
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posted 03-21-2001 04:35 PM
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You could always just take 70 % HNO3 and distill it the way you would for making HNO3 from KNO3 + H2SO4. like by vaccuum distilling it. this should work (i think) because the HNO3 has a lower BP and therefore would boil before the H2O that it is diluted with.


PHILOU Zrealone
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posted 04-04-2001 11:18 AM
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I see your points now but stil in industry they don't make 70% nor 100% from that process since you can only acheive a very low concentration without distillation!
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Bitter
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posted 04-04-2001 03:37 PM
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I don't know if this is a stupid idea, Philou, but I don't suppose you recommend electrolysing a low concentration of nitric acid to drive off the water, thus concentrating the nitrate, do you ? The electrodes would have to be graphite, of course, but this method, if it did work, would save us all the hassle of screwing around with NOx gasses and sulphuric acid.


CragHack
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posted 04-04-2001 03:59 PM
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that might work in theory but you have to consider the effect the electricty would have on the H+ and the NO3- ions that are in the solution. now that i brought the question up, would electrolyzing (for lack of a better word) have any effect on the other components (other than the water) when) in the acid?
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...Æ



PHILOU Zrealone
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posted 04-05-2001 07:49 AM
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That would cost a lot of energy; but yes, virtually it is possible, since all voltages and intensity are available quite easily from transformators, and that at certain voltage only certain reactions occurs.
------------------
"Life that deadly disease sexually transmitted".
"Chemistry is all what stinks and explode; Physic is all what never works! ;-p :-) :o)"



HMTD Factory
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posted 04-06-2001 02:28 AM
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If HNO3 do not decompose under electrolysis in aqeuous solution...like H2SO4...
But the electrode must not be graphite.
HNO3 can oxidize graphite. (Powder factory workers use HNO3 to remove micro carbon particles trapped inside their body tissue, finger nail for example.)



Bitter
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posted 04-06-2001 09:53 AM
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What do you suggest then ? Metals can't really be used otherwise they will react (don't forget it's incredibly strong acid we're making).
I don't think it is going to be appropriate to use platinum and gold and similar metals as electrodes due to cost, at 99% volume, these metals will probably begin to react with the acid anyway.



HMTD Factory
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posted 04-06-2001 12:39 PM
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No, platinum or gold don't react with HNO3 at
whatever concentration. Unless somebody is
drunk enough to add some HCl into HNO3.
Why will somebody need a thick rod of platinum or gold for electrode?

Maybe it's not well-known that platinum plated needle electrode is available from lab suppliers...These electrodes really go a long way...

[Marvin]

The action of formaldehyde on nitric acid is not catalyctic, it is a reducing agent. The mixture probably liberates NO2 and CO2. PHILOU I think was confused by the very old arc process, in which the 2% of NO2 was very difficult to produce az acid. In the early stages in germany, the weak nitric acid was used to make sodium nitrate, which was then distilled with conc sulphuric to produce fuming nitric acid. They built a concentrator plant based on magnesium nitrate to solve this problem. Since the Ostwald process took over, conc nitric acid is not a problem, as neerly pure NO2 can be produced. 99% nitric can be produced in a batch step with 50atm of oxygen, as has been discussed elsewhere, even miniscule amounts of NO2 in air (eg 0.1%) can be used to make fairly conc nitric acid 30-50%, this is not practical on an industrial scale though. Electrolysis doesnt work how youd think it would, as its impossible to liberate hydrogen from conc nitric acid (It gets reduced instead), concentration has to be achieved by crossed gas liberation, and by ionic mobility differences.

I dont like NO2, and NO2 doesnt like anyone. Forming it in order to concentrate nitric is the long way around a short problem, and likley to pose much more of a health risk than simply distilling az twice from equal volumes of conc sulphuric....

[ProdigyChild]

Some members think 'industrial' and use their easiest way to create highly concentrated nitric acid. Others try to reduce the need for critical chemical, i.e. chemicals that could raise the interest of some do gooders searching for 'potential terrorists'.

So even it's easy to use sulfuric acid for the purpose easily, it's nice to have other options, no matter, if a bit more poisonous substances are involved. If to avoid danger, then avoid explosives :)

I've read above, that highly concentrated NO2 or even liquid NO2 DOES react to higher conc. nitric. Even better, if the right amount of O2 is present at the same time (and the right amount of water).
Not that difficult really! From dilute HNO3 you can produce Fe(NO3)3, dry it at moderate heat. Further heating causes:

Fe(NO3)3 => 1/2 Fe2O3 + 3 NO2 + 3/2 O2

That's exactly the right ratio for turning NO2 and O2 + Water into HNO3!!
I've already decomposed this brown salt in very small amount and it works wonderful! Not more than 200-300° required, as far as I can estimate. (test tube over candle!)

Feels similar to destillation of HNO3, except you distill over a gas mixture into low conc. HNO3 (or even water). Not difficult to even produce some pressure, is it?
And I really wonder, if this process involves more danger due to NO2 compared to destillation. Cooling the acid would condense liquid NO2 on its surface...

I've read that alkali metals decompose like this:

NaNO3 => NaNO2 + 1/2 O2

We all know AN's decomposition(s)!

ALL OTHER salts should decompose like in the formula for iron salt above - according to one of my chemistry books. So maybe Ca(NO3)2 or Al(NO3)3 would also do the job.

Is there a catch somewhere, why this can't work as described??

Fucking hell, you could possibly build the apparatus out of steel, because
- **cold** conc. nitric does not dissolve Fe
- dry NO2 + O2 possibly, neither, not even in heat
==> High pressure reactor, closed by welding :D

[meselfs]

The pressure needs to be 50 bar, I've heard. This is basically impossible for someone without access to a some machinery, eg lathe & mill.

Steel I would never, ever trust with cold nitric acid, but according to Merck NO2 may be stored in steel reliably if the moisture content is less then 0.1%.

But note this: aluminum is not attacked by nitric acid. Creepy, aye?

[DF90]

Group 2 nitrates (for example Ca(NO3)2) decompose like this:

Ca(NO3)2 -> 2CaO + 4NO2 + O2

Not sure if this is still an ideal NO2/O2 mixture for dissolving in water/dil. nitric acid.

[DF90]

I completely forgot why i came onto this thread last time I posted :confused:

Basically the idea was making 100% nitric acid, by reacting lower concentration nitric acid with phosphorus pentoxide. The water in the lower conc. acid will react first to give phosphoric acid (H3PO4) Once all the water has reacted, the phosphorus pentoxide then reacts with the nitric acid:

6HNO3 + P2O5 -> 3N2O5 + 2H3PO4

The N2O[sub]5 can then be separated (no idea on how to do this experiment practically, just the theory :D), and dissolved in an equimolar amount of distilled water, yeilding 2 moles of 100% Nitric acid for every mole of N2O[sub]5 dissolved. The only downside of this method is obtaining the phosphorus pentoxide and the fact that it cannot be regenerated from the phosphoric acid produced in the reaction, unless of course you react the phosphoric acid with calcium carbonate, then heat the tricalcium phosphate produced with carbon and sand to over 1000C to distill off white phosphorus, which you can then burn in a sufficient supply of oxygen to yield phosphorus pentoxide again....

[209]

Probalby one of the most widely known method of producing nitric acid (to us chemists at least) is the H2S04 + KNO3. I have got buckets of KN03. Sulphuric on the other hand creates a small problem. I had less that 500 mills of pure H2S04 left and I can't afford to waste it on Nitric. I have got pretty much infinite amounts of drain opener that has a very large concentration of sulphuic, would this work to make nitric?

If this works, great! Or will I just end up with a liquid that is worth jackshit and a bunch of funky colours? Anyone know what the outcome concentration on the nitric would be from 94% Sulphuric?

+++++++++

These questions have been asked countless times, and the answers available to anyone who bothers to UTFSE.

NBK

[ETCS (Ret)]

The Magnesium Nitrate procedure for distilling high percentage Nitric Acid is workable, however it requires large quantities of anhydrous Magnesium Nitrate.

Fortunately, Magnesium Oxide is very inexpensive and low percentage Nitric Acid is relatively easy to make on a small scale.

There are new processes which have been patented for the electrolytic dehydration of Nitric Acid which may be possible to implement on a laboratory scale.

Search "nitric acid dehydration" and you'll find several links to the patents which make very stimulating reading.

[megalomania]

It is customary to provide a patent number if you have it. How recent is recent for that electrolytic method? I get over 15000 results using nitric acid dehydration, I don't want to spend weeks wading through that many results since all of them I browsed so far are false positives unrelated to nitric acid production.

[tmp]

Mega, I found 2 patents related to anhydrous HNO3 production via
electrolytic cells. In fact, if the patents are correct, N2O5 in HNO3 can also
be produced. I found patents 5181996 and 6200456 to be very interesting
reading to say the least.

http://www.patentstorm.us/patents/6200456-description.html

The date on 6200456 is March 13, 2001. Because I'm a fan of electrolysis
in general(chlorates/perchlorates) this may be my next project. :D:D:D

[megalomania]

That's what I was looking for... Check out the related class of patents, there are good dozen that seem promising: http://www.freepatentsonline.com/CCL-205-553.html

[ETCS (Ret)]

Mega, Tmp,

Sorry about not getting back to you with amplifying data - my phone line has been down for several days until ATT was able to repair it today. Thanks tmp for the yeomans input with your search results.

I know that searches can result in a lot of extraneous garbage so I should have mentioned that I use the Scroogle scraper which automatically filters most of the garbage out.

[Azido]

Say someone was low on H2SO4, but had an excess of nitrate salts (and water hopefully), could this method maybe save some valuable resources? Nitrate Salts decomposed to produce NO2, which is subsequently dissolved into water to form the 68% azeotropic acid, which is then concentrated using vacuum distillation with H2SO4? Or is that just me getting excited..

[penguin6636]

If NO2 will dissolve into HNO3 concentrating it, would NO2 suspended above HNO3 in a reaction vessel and brought below its boiling point react to concentrate the HNO3?

[megalomania]

NO2 reacts with water to form HNO3, so any means of getting the gas to contact water will work. The boiling point of NO2 is 21.1°C, so you could add liquid NO2 to water. The reaction forms NO, which escapes the liquid, and then reacts with air to form more NO2. Industrially they use either flowing water or water spray to mix with NO2 and air because this is the most efficient way found so far.