killswitch
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Urea pyrolysis
Now that new federal regulations have come into effect making ammonium nitrate extremely difficult to acquire, and forcing most makers of instant cold
packs to move to other substances, I'm interested in methods for producing nitrates without running my electrical bill into the triple digits. Urea
seems to be becoming much more available in the vacuum left by ammonium nitrate in fertilizer and cold pack formulations, so the combustion of urea to
CO2, H2O, and NO2 seems a fine replacement. Less convenient, obviously, but not as dangerous as electric-arc processes. My main concern is how to
control the temperature to ensure that diatomic nitrogen formation is minimized or eliminated, and that the H2O and NO2 come into optimum contact for
the best yield of HNO3. I'm contemplating a one-pot procedure wherein the NO2 and H2O combine with unreacted CO(NH2)2 to form urea nitrate, while
ammonia produced by hydrolysis of the urea combines to form ammonium nitrate. If this is too unpredictable or difficult to control, I will stick with
my original plan of simply replacing the arc chamber in your standard HNO3 generator with a urea pyrolysis device.
Edit: A device that doesn't make my yard smell like burnt piss would be great.
[Edited on 30-3-2012 by killswitch]
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mnick12
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I would imagine the pyrolysis of urea would be a very messy set of reactions. When heated strongyl urea goes under all sorts of condesations and
eliminations giving off ammonia gas, and forming all sorts of condensation products (biuret, cyanuric acid, and more). All of which are relativly
inert and resistant to further decompostion in the absence of extreme conditions. If you want to go from urea to nitrate you would probly be better
off feeding the urea to some nitrobacter and let them take care of the rest.
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killswitch
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Quote: Originally posted by mnick12  | | I would imagine the pyrolysis of urea would be a very messy set of reactions. When heated strongyl urea goes under all sorts of condesations and
eliminations giving off ammonia gas, and forming all sorts of condensation products (biuret, cyanuric acid, and more). All of which are relativly
inert and resistant to further decompostion in the absence of extreme conditions. If you want to go from urea to nitrate you would probly be better
off feeding the urea to some nitrobacter and let them take care of the rest. |
What about combusting the ammonia?
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weiming1998
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The combustion of ammonia without a catalyst results in: 4NH3+3O2===>2N2+6H2O, so that wouldn't work. With a platinum catalyst (some say that
copper works as well), however, the react will be like: 4NH3+5O2===>4NO+6H2O. This is the industrial way of producing nitric acid and related
nitrates. However, in a home setting, this requires either very sophisticated equipment or very smart design. To give you an idea of what it is like,
I'll write down the approximate setup (that my limited intelligence can think of)
First, you obviously will need the container that you are pyrolysing the urea in. A flat-bottomed flask will do. A glass tube needs to channel the
produced gasses to an oxidation chamber with some loose copper catalyst. This chamber can probably be a three-necked flask, with one opening being the
gasses that a channeled through, one opening some air from a fish pump or some other source, and the final one leading to another glass tube. Both the
first and the second flask needs to be heated. The final glass tube leads to a beaker of either cold H2O or H2O2, which the gases will dissolve in,
and the depleted air from the fish pump escaping. Not to say that the three-necked flask might crack from heating it empty.
Now, the products produced. Urea pyrolyzes into: CO(NH2)2===>NH3+HCNO. The HCNO hydrolyzes in water to produce NH3 and CO2, which meets in water to
form NH4CO3, which reacts with the HNO3 to form NH4NO3. So your end product is a mixture of HNO3 and NH4NO3.
If you have glass tubes, a beaker, a three-necked flask, fine copper catalysts, a flat-bottomed flask and a pumped supply of air, this might be worth
a try. But if you don't, and don't consider welding metal together to form the apparatus, then that won't probably work.
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bbartlog
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If you're going to try catalytic oxidation of ammonia then there is no need to be pyrolyzing the urea. Just mix it in water with slaked lime (or other
strong base) and hydrolyze to ammonia. Gentle heat to drive the ammonia out of solution and speed the reaction might be desirable. However, I expect
it would take a lot of tinkering to get non-abysmal yields of NO2 with such a setup.
The less you bet, the more you lose when you win.
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killswitch
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And by copper catalyst you mean finely powdered elemental copper? Or do you mean some kind of organometallic compound?
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killswitch
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| Quote: Originally posted by weiming1998 |
If you have glass tubes, a beaker, a three-necked flask, fine copper catalysts, a flat-bottomed flask and a pumped supply of air, this might be worth
a try. But if you don't, and don't consider welding metal together to form the apparatus, then that won't probably work. |
Put that way, I'm sure one of the forum-goers could give it a try and report their results, or at least provide an illustration or picture to give the
gist of how the apparatus would look.
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weiming1998
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| Quote: Originally posted by killswitch | | And by copper catalyst you mean finely powdered elemental copper? Or do you mean some kind of organometallic compound? |
Finely powdered copper, or copper "wools" like steel wool except made of copper. No need for organocopper compounds. If copper doesn't work, then I
guess you'll have to spend quite a bit of money to buy some platinum wire to use as a catalyst.
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watson.fawkes
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The two catalysts used in industry are
platinum and cobalt oxide. Cobalt oxide is the new one; last I looked a few years ago there were only two in operation. Every other one was using
platinum, and platinum conservation and recovery is a big deal in these plants for economic operation.
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dann2
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Is this any addition?
A search under 'thermal decompositon of urea' brings up some reading.
Dann2
Attachment: urea_decom.pdf (164kB)
This file has been downloaded 1686 times
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shannon dove
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I know that nobody believes me, but I made nitric acid by running ammonia and air through a red hot copper tube. There was no other catalyst but the
copper tubing. Although it was a low yield and not very efficient.
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unionised
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I believe you because I have done the same thing. I was trying to prepare nitrogen by reacting air and ammonia ( to get N2 and water, which I could
trap easily). I did use a copper oxide catalyst, but the inside of a copper pipe would have given you that.
The yield of NOx wasn't good, but it was a lot higher than I wanted.
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shannon dove
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Does anyone here have any knowledge about pyrolysis of protein? Would it be similar to urea pyrolysis? Maybe mix hamburger with slaked lime then
distill ammonia out of it.
Yea I have searched it, but I like to here y'alls opinion about whether its worth the trouble. Maybe it's very low yield (inefficient) .
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12AX7
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There's a protein assay reaction, I believe using concentrated sulfuric acid to digest protein into things like elemental nitrogen. I want to say
ammonia is involved somehow, but that can't be, it would remain in solution as ammonium. Not much help from that memory bank...
Ammonia used to be "spirit of hartshorn" or something like that by destructively distilling hooves; I don't think lime is required (though I would
expect it improves yield).
I once tried to distill urea through a heater copper pipe, with the assistance of air, and I thought I saw some brownish gasses come from the
apparatus, but never smelled the characteristic sharp odor of NO2, so it probably wasn't working. Catalysts need huge surface areas anyway; instead
of a copper pipe, a better approach might be, say, glass wool, soaked in a solution of Cu(II) then reduced quickly to Cu(I) which precipitates
microscopic Cu2O, etc. Then stuff this loaded wool into the heated pipe and see what happens. Also need to get the temperature and urea-air
concentration correct. Lots of process variables to play with, which if you have the resources to control (pumps and thermostats and whatnot), is
pretty easy, but if you don't, you're just pissing in the wind...
Tim
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Glucose Oxidase
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I don't know if this is true because i read it on a thread somewhere -sorry i cant cite it because i can't find it- anyway the thread says that
heating urea with potassium carbonate or hydroxide would form potassium cyanate which in turn could be oxidized to potassium nitrate using oxidizing
compounds such as potassium chlorate but some carbonates should be added to keep the reaction under control and you know the to produce NH4NO3
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White Yeti
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If you had an ozone generator, you could make ammonium nitrate by oxidising an aqueous solution of ammonia. The aqueous ammonia can be obtained by
mixing urea with slaked lime as mentioned above. An ozone generator is pushing the limits, but so is the pyrolysis of proteins.
I'm particularly interested in the generation of NOx by passing ammonia and air through copper tubing. Could copper oxide powder serve as a catalyst?
"Ja, Kalzium, das ist alles!" -Otto Loewi
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Joe3
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Its not that hard to make NO2. The problem is the expense of the platnium.
When I was a kid in the 1960's we had our own nitric acid plant. It was completly homemade. it wasent that efficient but it made lots of 40% acid.
The reactor was nothing more that a piece of pipe with a rolled up piece of platnium cloth in it. We even made the cloth on a little loom. Even made
the thread by hand on drawing dies.
But the process basicly was like this.
High pressure ammonia and air was heated and pushed thru the reactor then from the reactor it went to a cooler then from the cooler into a small
still.
The reactor gave off lots of heat and needed to be cooled.
But it is that easy.
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Texium
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Thread Moved
20-11-2023 at 13:02 |
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