exodia
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re-use NO2 and Cl2
Hi there, I'm looking for an efficient way of converting Cl2 and NO2 back to HNO3 and HCl.
is not for anything in particular just for fun, and because of the fact that I am doing at the moment lots of experimentation with MnO2 and HCl and
other clorine production reactions, and as well obtaining various nitrates with HNO3 and the respective metals.
So I though it will be fun getting rid of all this nasty fumes and turn them to something useful.
the Cl2 seems easy enough: bubble in H2O and wait (from another post here in SM it should produce HCl and HClO in equilibrium, being the HClO unstable
and decomposing into HCl.
for the NO2 being bubbled in H2O though I haven't found much, will it turn straight away into HNO3?
my main questions are, is this as easy as it sounds, doing this and then boiling-concentrating/distilling until azeotrope?
and how do I improve the gas absorption by the water, if I just submerge a plastic tube into a H2O beaker I suppose I'll loose lots of gas bubbling
out of solution, and I'm not really up to closing the system to maximise absorption (or explosion  )
Many Thanks everyone
[Edited on 25-12-2016 by exodia]
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Chemetix
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NO2 has been my project recently; I went for a column packed with glass and a little water and bubbled the gas into it. Works better than I thought!
Have fun. Stay safe - NO2 is nasty stuff for the lungs.
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clearly_not_atara
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NO2 dissolves in water in the presence of oxygen to become nitric acid, although the reaction is slow so the NO2 must be immobilized somehow. Chlorine
however will only dissolve in alkaline water producing (relatively) stable hypochlorite; reducing Cl2 to HCl is nontrivial but aluminum should do the
trick (very vigorous rxn). Although you might get hate mail for synthesizing AlCl3 just to hydrolyse it lol
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Tsjerk
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NO2 with water forms HNO2 and NO, you can bubble into H2O2 of appropriate concentration directly to convert to HNO3. Oxygen also works as oxydizer but
it's harder to regulate in terms of right amount added to the reaction as it is a gas.
Edit ; what clearly_not_atara says...
[Edited on 25-12-2016 by Tsjerk]
[Edited on 25-12-2016 by Tsjerk]
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exodia
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so do you have any idea to minimise gas loses?
I have bubbled gasses in water before and part of that gas just rises up an bubbles out of solution before dissolving or reacting.
I don't want that: second for the product loses, but first because they are nasty gases and I don't want them escaping (I have done a gas scrubber
before, but with this I am trying to actually recycle them)
I do have an idea of a set up which would consist in several glass recipients connected one to another so the gas that escapes can get into the next
chamber, but unfortunately I don't have enough glassware for that at the moment.
so I wanted a way of keeping the gas in place until it reacted fully with the water (and closing the system is the easiest way but dangerous as well
so I'm not going to go there)
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Chemetix
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Quote: Originally posted by WGTR  | | Quote: Originally posted by Chemetix |
In the SM library I found Absorption of Nitrous Gasses, a 1933 text but an exhaustive tome on the dynamics of NO2 absorption and quite
instructive. |
I bought an original copy of that. Had to have it shipped from Australia to the U.S. I considered it well worth the price, and it occupies a place
of honor on the bookshelf.
If you want to, you can adsorb NO2 onto silica gel.
https://www.sciencemadness.org/whisper/viewthread.php?tid=48...
The NO just passes through unaffected. It's best if the gasses are dry, since water is also adsorbed. In this way, dilute streams of NO2
can be concentrated, allowing an easier conversion into nitric acid, and at a higher acid concentration. Also, the silica gel is a handy way of
storing NO2. To release the NO2 vapors, the silica gel can be heated up. In the linked video, the gasses weren't dried, so
some water was also getting adsorbed.
I'm working (off and on) on a Birkeland-Eyde reactor design. By drying the gasses going into the reactor, allowing the exit gasses time to oxidize,
and then adsorbing the NO2 onto a silica gel column, I'm able to easily measure the efficiency by comparing the before and after weights of
the adsorption tube.
Since you're producing water in the reaction (?), perhaps that could be adsorbed in a drying column right after the gasses cool down, before the NO
has time to oxidize. After time spent in the oxidation chamber, then the resulting gasses could be adsorbed in a second column, that could be
weighed...? Just an idea.
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Sorry for the quote of a quote of a quote, but this has been discussed here quite a bit.
https://www.sciencemadness.org/whisper/viewthread.php?tid=71...
[Edited on 26-12-2016 by Chemetix]
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AJKOER
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Adding Cl2 to two parts NO2 into the same water should work also. I have performed for dilute solutions in a closed system . Expected net aqueous
reactions (upon shaking to remove gas phase products):
Cl2 + H2O = HCl + HOCl
2 NO2 + H2O = HNO2 + HNO3
HOCl + HNO2 → HCl + HNO3
Net: Cl2 + 2 NO2 + 2 H2O → 2 HCl + 2 HNO3
Boiling to separate the acids being the HCl is more volatile may work (not attempted), but likely dependent on acid concentration and temperature.
Caution: highly corrosive/toxic gases (NOCl, NO2,..) could be experienced in an open system!
Prior comment by Woelen:
| Quote: Originally posted by woelen | I have actually done some experimenting with Cl2 and NOx.
Cl2 and NO give orange gaseous ONCl, which quickly hydrolyses in water, but not in concentrated HCl. In the latter it dissolves, giving very nice
orange solutions, looking very much like solutions of K2Cr2O7. ONCl reacts with water, giving HCl and HNO2, which in turn gives HNO3 and NO.
Dry Cl2 and NO2 do not seem to react. The mix of gases becomes brown, not looking very nice. On addition of water, however, the mix of gases quickly
dissolves and a colorless acidic solution is obtained. I tested this and it contains chloride. The other part most likely is nitric acid. I am quite
sure that the reaction is as follows:
2NO2 + Cl2 + 2H2O --> 2HNO3 + 2HCl |
Link: http://www.sciencemadness.org/talk/viewthread.php?tid=23199
[Edited on 26-12-2016 by AJKOER]
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Tsjerk
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Cl- in HNO3 give ONCl which cannot be separated by distillation
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AJKOER
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| Quote: Originally posted by AndersHoveland | | Quote: Originally posted by woelen | | Cl2 and NO give orange gaseous ONCl, which quickly hydrolyses in water, but not in concentrated HCl. In the latter it dissolves, giving very nice
orange solutions, looking very much like solutions of K2Cr2O7. ONCl reacts with water, giving HCl and HNO2, which in turn gives HNO3 and NO.
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It is obviously in equilibrium.
Nitric and hydrochloric acids in concentrated solution have equilibrium with nitrosyl chloride and chlorine:
HNO3 + 3 HCl <==> 2 H2O + NOCl + Cl2
This is the same equilibrium that allows aqua regia to dissolve gold. The reaction shifts to the left in more dilute aqueous solution, or to the right
in more concentrated acidic solutions.
Since nitrosyl chloride does indeed hydrolyze in water to HNO2 and HCl, the equilibrium could also be written as:
HNO3 + 2 HCl <==> HNO2 + H2O + Cl2
If I recall correctly, aqueous solutions of nitrogen dioxide are in equilibrium with nitric acid and nitric oxide. The equilibrium can shift either
way depending on conditions.
3 NO2 + H2O <==> 2 HNO3(aq) + NO
2 HNO2 <==> H2O + NO2 + NO
So we could also write the equilibrium as:
4 HNO3 + 8 HCl <==> 2 NO2 + 2 NOCl + 6 H2O + 3 Cl2
Obviously nitric oxide is not going to be able to accumulate in the presence of chlorine, since it will just be immediately oxidized.
In the absence of water (or also as Woelen has demonsrated in conc. HCl) nitric oxide is oxidized by chlorine to nitrosyl chloride. In more dilute
aqueous solutions, chlorine oxidizes it to nitric acid.........
[Edited on 1-2-2013 by AndersHoveland] |
Link, same thread referenced above: http://www.sciencemadness.org/talk/viewthread.php?tid=23199
Note, in the above cited reactions, the implication is that there are two to three parts of chloride (from HCl) to HNO3 for the reaction equilibrium
to shift to the creation of NOCl.
As such, if one starts to boil a mix of equal parts of HCl and HNO3, the further loss of the volatile HCl stills does not favor NOCl, in my opinion.
But, not having attempted the separation, I am leaving the issue open to verification.
[Edited on 27-12-2016 by AJKOER]
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ave369
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| Quote: Originally posted by AJKOER | Adding Cl2 to two parts NO2 into the same water should work also. I have performed for dilute solutions in a closed system . Expected net aqueous
reactions (upon shaking to remove gas phase products):
Cl2 + H2O = HCl + HOCl
2 NO2 + H2O = HNO2 + HNO3
HOCl + HNO2 → HCl + HNO3
Net: Cl2 + 2 NO2 + 2 H2O → 2 HCl + 2 HNO3
[Edited on 26-12-2016 by AJKOER] |
So, in a sense, the mixture of NO2 and Cl2 is the anhydride of aqua regia?
Smells like ammonia....
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woelen
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Well, if you phrase it that way . . .
I would explain it somewhat differently.
A 2 : 1 molar mix of NO2 and Cl2 gives HNO3 and HCl in a molar 2 : 2 ratio, when bubbled through water. NO2 can be considered the anhydride of HNO2
and HNO3 (in a 1 : 1 ratio). This is what actually happens in water. The HNO2 in turn reacts with Cl2 and water to form HNO3 and 2HCl.
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clearly_not_atara
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If your anhydride-forming equation is formally O2NOH + HCl >> H2O + O2NCl then the anhydride you're looking for is nitryl chloride. However the
hydrolysis of NO2Cl forms HOCl + NO2H! But it can be formed from HSO3Cl + HNO3:
http://pubs.rsc.org/en/Content/ArticleLanding/1958/JR/JR9580...
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woelen
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Formation of HOCl and NO2H from NO2Cl may be an intermediate stop, but these immediately will react to form HCl and HNO3. So in practice you indeed
can consider NO2Cl as a mixed anhydride of HNO3 and HCl.
HNO2 can act as oxidizer, but also as reductor. HOCl is a very strong oxidizer and it immediately oxidizes HNO2. I know this from my own experience in
experiments I have done with acidified nitrites and bleach.
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Melgar
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Considering how cheap HCl is, I'm not sure why you wouldn't just want to save the Cl2? You can make your own TCCA by bubbling Cl2 into a basified
solution of cyanuric acid, and cyanuric acid is what's left over when you heat urea hot enough to give off anhydrous ammonia gas. Or bubble Cl2 into
benzyl alcohol to get benzoyl chloride, which you can use to make acid chlorides.
As for NO2, I just started mixing 30% H2O2 into my nitric acid, which immediately oxidizes the NO2 back to HNO3 as soon as it forms. I still get them
when using sodium nitrite, but not enough to think about trying to collect them. Bubbling them into H2O2 would oxidize them back to nitric acid
though, I imagine.
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