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agorot
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What about this:
quoting wikipedia:
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Magnesium nitride can be produced by burning magnesium metal in a pure nitrogen atmosphere.
3 Mg + N2 → Mg3N2
Mg3N2 + 6 H2O → 3 Mg(OH)2 + 2 NH3
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magnesium isn't that hard to find, and you could use the waste hydroxide if you have a stomach ache 
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chief
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Fort this reaction Mg is either ignited or at least glowed:
==> A thicker layer of Mg-powder is used ...
The O2 is consumed first, so after the burning
==> the upper layers of the educt contain oxide,
==> while the lower layers are the nitride: Quasi the O2 is filtered out of the air through burning with the upper layers of the Mg ...
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S.C. Wack
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http://books.google.com/books?id=0ekNIaJX3-YC&pg=PA88
This book states here that 100 grams of osmium powder were used for a demonstration on July 2.
I wonder if this is the low hanging fruit.
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watson.fawkes
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Thanks for posting this book reference. The beginning of the
section you linked to, the one on the creation of the ammonia synthesis, stresses the importance of the high-pressure technology (pump, seals and
values explicitly), to the extent that Haber thanked his engineer and machinist in his Nobel lecture. (Good for him.)
The importance of this high-pressure technology means that, for the amateur chemist, the apparatus itself is going to be the dominant expense involved
in doing this. In contrast, in an industrial context, the operating costs (predominantly energy inputs) of a reactor dominate. The critical ratio is
that between capital costs (the apparatus) and operating costs. These are different for amateurs and industry. Now the effect of a less efficient
catalyst has an effect on the operating cost, but that has to be weighed against how much that machine is ever going to produce. A less efficient
catalyst means that the recirculation ratio is higher, which means more pumping. So the trade-off is between the energy cost for the output over the
life of the machine and the cost of the catalyst.
Therefore, I can't recommend osmium, expensive, over the iron-based (and other) catalysts for a small-scale machine, at least for a first catalyst. I
make this recommendation on economic grounds, that you don't need to spend the money for the desired output. On the other hand, if you want to study
catalysis itself, knock yourself out.
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chief
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The link to the book is very interesting ...
==> Steel embrittles from the H2, and vessels burst after a while ...
==> lining with silver or copper doesn't work ...
So maybe thin glass-pipes, within a strong containment (in case something fails), are the way to go ...
==> 1 kg of Quartz-tubes is at 20 € ..., various diameters; _hot_ welding-flame (with oxyen) is needed for handling ... ; good UV-shield is
essential ...
==============
Still the pressure-source is needed ...
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densest
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@not_important - thanks for the clarification about the ceramic. Is it correct that the proton emerges as a single atom and thus is reactive enough
to disturb the N-N triple bond?
If so, it's a real shame that passing air over an oxygen-conducting ceramic doesn't produce NOx. I need to learn how to calculate the thermodynamics
again 
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mr.crow
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It depends on how much ammonia you want to make. Maybe just for shits and giggles so you can sniff it.
A reaction tube, heat exchanger, radiator and circulation pump should be good enough. The ammonia will turn into a liquid at that pressure and can be
separated to drive it forward.
According to wikipedia (yeah I know...) hydrogen embrittlement can be prevented by baking the hydrogen out of the metal within 4 hours.
And cheif, whats with the horrible grammar?
Double, double toil and trouble; Fire burn, and caldron bubble
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chief
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Horrible grammar ? Thats worthy german grammar, refined version ...
==> ... german invention here too
===================
Maybe some sort of "periodic" pumping might do it:
==> The pressure built up to as much bar as the compressor can handle, filling a "tank" ...
==> Then closing the valve to the compressor, and heating ... : Gives extra-pressure
From 300 Kelvin to maybe 600 the pressure should double, to 900 K it should triple ...
Required would be then a compressor that can make 60-90 bar, a good valve, and a tank that can store the gases at 200 bar ..., and another valve that
connects the tank to the conversion-unit ...
Would be a batch-wise compressing ... ..., batches as large as the tank ... ; tank would have to be somewhat larger than the conversion-tubing with
the catalyst, so the pressure would not drop too much upon opening valve Nr. 2 (into the conversion-unit)
The pressure-rise upon heating could be made higher by cooling first, as long as the compressor works: Thereby more gas would fit into the tank, that
could be heated for pressure-buildup ...
===========================
Ultimately a periodic thing, maybe at last even some car-engine could be abused: Compression only 10 bar, but many cycles per second ...
==> of a 4-cylinder-engine maybe 3 for the work, and 1 for the NOx/NH3/whatever-generation ...
==> lot's of people like hacking car-engines, someone could succeed, many would follow, could "democratize" the NH3-production, would be much safer
for the lower pressures ...
==> Temperatures in the car-engine upon compression anyhow reach the high required values ...
[Edited on 15-5-2010 by chief]
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watson.fawkes
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Quote: Originally posted by densest  | @not_important - thanks for the clarification about the ceramic. Is it correct that the proton emerges as a single atom and thus is reactive enough
to disturb the N-N triple bond?
If so, it's a real shame that passing air over an oxygen-conducting ceramic doesn't produce NOx. I need to learn how to calculate the thermodynamics
again |
In an ionic-proton conductor, the
proton does indeed conduct through the ceramic lattice as a "naked" ionic proton. Some of the proton-only conductors have lattice spacing small enough
that atomic H can't form inside the lattice, not even as a metastable state. Other materials have a predominance of naked protons, but (almost
certainly) with some population partition that includes atomic H. The ionization energy of H is 13.6 eV, just enormous compared to most chemical bond
energies, and so it's very reactive. Indeed, I have to imagine that will react with the very first thing it encounters, which is almost always
something adsorbed on the crystal surface. The problem, then, is that to disturb the N2 bond in any quantity, that N2 needs to be an adsorbed species.
You can do this; there are, after all, the zeolites used for N2 separation. The bigger problem is that there's an electric field across this ceramic
and, barring clever artifice, the predominant adsorbed species are going to be ionic, outcompeting the N2 for surface area. Presumably you want this
transient N2(+) species to react with something, and that something is likely to ionize more readily than N2. It's not that this is all impossible,
but it's also anything but obvious.
Furthermore, what you need is a material that adsorbs N2 preferentially and is also a proton conductor. So what you have is a materials science
problem. In my alternate life that I am not living, I would be researching this class of topics; it's completely fascinating. As for research
problems, I would not doubt that there exists some ceramic material that can produce NOx out of air. On the other hand, the search space of potential
materials is, um, rather large.
(Alternately, you can use high pressure to force a higher adsorption population. The only problem there is that most of these ionic conductors only
conduct ionically at rather elevated temperatures, say 600° C. That means you've now got mechanical problems just like the Haber process
itself has.)
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peach
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Is that Swagelok he's got on there?
Nice thread.
I was reading around about it just out of interest, not really because I need ammonia. It would indeed be fun to copy his table top machine for the
sake of seeing it again. It's a shame we didn't start the thread earlier on, then we could have possibly had one working by 2009, to mark the century
on from his demonstration of it.
A fridge compressor will go over 500psi - I think I've seen one I took apart running at about 600 or 700. But you'd need filters in there to get all
the oil out of the stream.
The pressure washer idea is good, but the cylinder would be the way to go; particularly if the washer is only going to be used to produce one charge
of gas (not recirculate it). It does look like he's running a belt driven pump to charge / recirculate the gas in there. If one was doing it for the
historical accuracy, a cylinder might be cheating.
I'd be happy with a cup per day, or less. Which means it could possibly be done with lengths of normal diameters of Swagelok. That would also lower
the safety issues. As someone pointed out early on, that stuffs still expensive, but it is rated above those requirements.
{edit} In the wiki article, it says they demonstrated it working from air. So the pump is just running straight into that (not recirculating) and it's
injecting air? Are they using zeolite to separate out the oxygen perhaps?
[Edited on 19-6-2011 by peach]
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IndependentBoffin
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| Quote: Originally posted by roamingnome |
I believe it is quite possible. You may have seen pictures of the original apparatus.
The French techniques have worked with higher pressures up to 10,000 psi in small diameter tubes which give a larger single pass yield of ammonia.
Technology these days is left for the large corporation that will safely deliver products to the consumer.
There is alot of details to consider of course
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Easy way to get high pressures at home is to scavenge a Diesel engine from an old car. Diesel engines have compression ratios (CR) of 14 - 23 to 1.
10,000 psi = 68.9 MPa
Assuming adiabatic compression:
P<sub>2</sub>/P<sub>1</sub> = (V<sub>1</sub>/P<sub>2</sub> <sup>γ</sup>
The following table therefore gives the theoretical ideal cylinder pressures for a diesel engines:
CR _Pressure
14 _40.2MPa
15 _44.3MPa
16 _48.5MPa
17 _52.8MPa
18 _57.2MPa
19 _61.7MPa
20 _66.3MPa
21 _71.0MPa
22 _75.8MPa
23 _80.6MPa
As you can see any Diesel Engine with a CR > 20 will get you the desired pressures. I wonder what happens if you take a 4 cylinder engine, modify
the fuel intakes of 1 - 2 cylinders to accept a N<sub>2</sub> + H<sub>2</sub> feed and collect the ammonia at the exhaust?
For better efficiency you could even feed the exhaust from one cylinder into the adjacent one to give your N<sub>2</sub> +
H<sub>2</sub> mixture two chances to produce ammonia
I can sell the following:
1) Various high purity non-ferrous metals - Ni, Co, Ta, Zr, Mo, Ti, Nb.
2) Alkex para-aramid Korean Kevlar analogue fabric (about 50% Du Pont's prices)
3) NdFeB magnets
4) High purity technical ceramics
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jimmyboy
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I think your biggest problem will be getting the pressure - the heat can be supplied by nichrome and insulation - why waste all that money on
compressors? an ordinary fridge compressor could never attain the pressures you need - an airtight steel piston and a hydraulic jack would work though
- find a steel cylinder drill a hole for a schrader valve and one for a release and two more to pass the heat element inside - tap some threads and
seal with brass parts/solder - inject the gas mix and crush with the jack - open the release for the ammonia - this will give you a small amount of
ammonia at a time but not continuous - considering your budget this may be the only feasible way unless you are skilled in the art of metalworking - I
would probably start looking for an old engine block for your piston and cylinder and test the rings/seal with a strong pressure guage - bore and
adjust as needed..
with an old block the ports are already drilled
just some ideas
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experimenter
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What if you react nitrogen and hydrogen together with the help of an electric arc, like in the Birkeland–Eyde process?
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AndersHoveland
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| Quote: Originally posted by agorot |
Unfortunately this reaction doesn't occur:
(B) 2 Li3N (s) + 3H2 (l) → 6 Li (s) + 2 NH3 (g)
I did some research and supposedly, this is the reaction that happens instead:
(C) Li3N (s) + 2 H2 (g) → LiNH2 (s) + 2 LiH (s)
Theoretically, if you could get equation (B) to work, instead of equation (C), your lithium would not be used up
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Reaction (C) is reversible at 270 °C.
When heated, lithium amide (LiNH2) decomposes to lithium imide (Li2NH) and gaseous ammonia (NH3).
(for what scarce information could be found about "sodium imide" you can read https://sites.google.com/site/ecpreparation/sodium-amide-imi... )
One would think that, with heat, nitrogen could be reacted with lithium hydride to form ammonia
(6)LiH + (2)N2 --> (2)Li2NH + NH3
and the lithium imide could be recycled by heating with hydrogen.
Li2NH + H2 --> LiNH2 + LiH
| Quote: Originally posted by JohnWW | | Why use rare and expensive Li for such a purpose? You could just as easily use Na, although it does not slowly combine with N2 like Li, but instead
reacts very quickly with it, and may possibly be induced to burn in it. You could also use K, which spontaneously ignites in N2, and besides K3N, may
also form a pernitride K2N2 and supernitride KN2. However, with Na and K, you would have to safely contain the reaction somehow because of the large
amount of heat rapidly generated. |
This is actually a common misconception. Interestingly, lithium is the only alkali metal which burns in nitrogen. The others, including sodium and
potassium, are unreactive towards nitrogen, even when heated. This is somewhat paradoxical because sodium, and especially potassium, are generally
much more reactive than lithium. True nitride ions (with three extra electrons and not covalently bonded) are not very stable. It is
not favorable for three extra electrons to occupy the smaller outer orbital of a nitrogen atom. Lithium ions are slightly acidic and can covalently
bond to nitrogen. In the crystal structure of lithium nitride the nitrogen atoms have only one extra electron, while being covelently bonded to two
other lithium atoms. One of the reasons why oxygen and nitrogen prefer to exist as diatomic elements is the repelling from the lone pairs. With only
two atoms bonded together, this gives the lone pairs more space. Other elements have few lone pairs, or a biger atomic orbital, which means more space
for the lone pairs. As far as I am aware, compounds of pernitride and supernitride have never been prepared. The potassium ion would likely attract
both electrons towards the closer nitrogen atom of a pernitride anion, leading to two of the anions dimerizing into (-2)N--N=N--N(-2). This
intermediate would likely spontaneously decay into nitride ions and azide ions, if not elemental nitrogen. Because of the great stability of diatomic
nitrogen, it is unlikely that nitrogen can form anions which would correspond to the peroxide and superoxide anions of oxygen. Azide anions are
somwewhat of an exception because there are three electron-withdrawing nitrogen atoms to attract the extra electron, which resonates around.
(-)N=N(+)=N(-) <--> NΞN(+)--N(-2)
[Edited on 16-7-2011 by AndersHoveland]
I'm not saying let's go kill all the stupid people...I'm just saying lets remove all the warning labels and let the problem sort itself out.
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Aperturescience27
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I apologize if someone's already suggested this, but there's one simple (yet not necessarily efficient) solution: an electrolytic cell with molten
lithium hydroxide (M.P. 462 C) producing metallic lithium, which reacts with nitrogen to form lithium nitride, which reacts with water to form ammonia
and lithium hydroxide. Consumes only nitrogen and water, produces ammonia and oxygen (oxygen at the anode). Design would be difficult, but not
expensive (unless you had to use an expensive material for the anode, which would of course have to be resistant to corrosion by both oxygen and
lithium hydroxide, and you couldn't use carbon because carbon dioxide would react with the lithium hydroxide and produce lithium carbonate), and you
wouldn't need high pressures. Air could probably be used as a nitrogen source, because the lithium oxide produced would just end up as lithium
hydroxide, and lithium doesn't produce peroxides or superoxides in air. Hopefully the lithium nitride would dissolve in the lithium hydroxide, because
then the air or nitrogen input, which would go into the cathode compartment, and the water input/ammonia output could be separate. The oxygen would
come off separately from the anode compartment. You might get some hydrogen at the cathode, from water reacting with lithium metal, which could be
dangerous.
Also, AndersHoveland is right, other alkali metals don't form nitrides. Alkaline earth metals do, but their hydroxides have really high melting
points.
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bbartlog
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If the topic is the Haber process (as the thread title states), this is OT. If you want to restate the problem as 'how do I get ammonia', your
solution is notable mainly for being *even less practical* than the tabletop Haber process idea.
The less you bet, the more you lose when you win.
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Aperturescience27
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I'm not the only one who's OT. Just saying. Anyway, the Haber process is really better suited to large-scale production. You have to circulate the N2
and H2 a whole bunch of times, getting a little bit of ammonia out each cycle, because of equilibrium, and shifting the equilibrium to the right
causes slower reaction rate.
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Fluorite
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https://m.youtube.com/watch?v=8LriocEzpC0 They tried this but the arc can split ammonia again to N2 and H2
But this can be limited if you add acid like hcl to make nonvolatile salt?
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symboom
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Here is a small reactor
It uses iron wool as a catalyst
Nitrogen and hydrogen
https://www.youtube.com/watch?v=S3j8dCweN4A
[Edited on 18-11-2020 by symboom]
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Fluorite
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Can I use stainless steel wool?
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itsallgoodjames
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Most likely not, and even if it did, it'd probably be incredibly inefficient. Iron acts as a catylist, and it's one of the few metals to do so. The
only other that I'm aware of are ruthenium, uranium and osmium. It might be worth a try, but I doubt it'd work all that well.
Nuclear physics is neat. It's a shame it's so regulated...
Now that I think about it, that's probably a good thing. Still annoying though.
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clearly_not_atara
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big revival energy :/
symboom is on the right track. The easiest way to mimic Haber isn't to literally copy him unless you have a professional machinist on
call (he did!). Instead you can probably find some lab-scale Haber reactors designed more recently that take advantage of the last 100 years
of research in chemistry.
If you ask me the future is artificial nitrogenase:
https://onlinelibrary.wiley.com/doi/pdf/10.1002/tcr.20160002...
[Edited on 04-20-1969 by clearly_not_atara]
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gerrockium
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recently there was a paper about using manganese powder at high temperature, manganese forms nitride, then manganese is recovered venting ammonia.
https://doi.org/10.1002/ceat.202000154
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