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Author: Subject: Ostwald style nitric production
Magpie
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[*] posted on 25-12-2016 at 08:00


Here's some recollections from my lab experience, FYI:

1. A porous catalyst support can be made from landscaping lava rock. I made some 4-8 mesh as a support for H3PO4 catalyst. It's extremely hard, however, and difficult to reduce to the desired particle size.

Pumice is available as an abrasive at pool supply stores. This might make a good catalyst support.

2. I made anhydrous NH3 by boiling it out of a water solution then passing it through a column loaded with KOH flakes.




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[*] posted on 25-12-2016 at 12:36


What I have learnt from this build is the ammonia oxidation reaction is a robust one. It doesn't need a finely tuned set of operating parameters. And there are probably dozens of suitable catalysts out there, I had a few lined up to test and it turned out cobalt was active enough and so I stuck with it. Nickle oxide was my next bet.

The support bed can be just about anything- dirt! The catalyst doesn't seem to care what it's on so long as it holds up at the temperatures and gives you enough support, but volcanic rock or pumice (also a volcanic rock) would be perfect. I was looking to smash up and grind a piece of kiln furniture, and I did try breaking a fire brick but got more dust than screenings.

The tube - how many other options are there?
I'd say the reaction can be lowered to 500C, which is borosilicate range of working temps, just pack more catalyst into a longer tube to allow for the slower rate of reaction. I have eyed off a piece of tubing used for thermocouples, a pyro-ceramic of some sorts. A suitable alternative would be something like a copper tube with some glass tape wound around it( automotive exhaust shop), make a paint with sodium silicate and some silica flour(inhalation hazard) from a ceramics supply. Then some nichrome wire around that and more insulation over the top.

I'd say if you get fairly anhydrous NH3 without the CO2 at an optimum air mix, the reaction might just self sustain the heating. Nickle oxide I strongly suspect to be more active than the cobalt, but that's a hunch at this stage.


[Edited on 25-12-2016 by Chemetix]
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[*] posted on 25-12-2016 at 12:51


Quote: Originally posted by WGTR  
Let me know the inner diameter of the catalyst tube.


Sorry I forgot to answer that; 8mm ID.
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[*] posted on 25-12-2016 at 17:23




[Edited on 26-12-2016 by Chemetix]
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[*] posted on 25-12-2016 at 17:49


Quote: Originally posted by Chemetix  

The reactor tube runs into the converted 2L sep. funnel which admits air via the custom condenser fitting.


I'm a little confused here: are you admitting air into the 2L sep funnel absorber as well as ahead of the reactor?


Quote: Originally posted by Chemetix  

This shot shows where the ammonia air mixture is fed into the reaction zone, the nice red glow is transmitted up the quartz.


Clearly you are admitting air here ahead of the reactor. I assume this is the slightly pressurized source from the compressor?




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[*] posted on 25-12-2016 at 18:13


Yes I can add air ahead of the reactor, in fact you need to:

4NH3 +5 O2 => 2NO + 3H2O

In the sep funnel the reaction:

2NO+ O2 => 2NO2

means you should need to add air as well. The ammonia air mixture was quite oxygen rich and so the unreacted O2 formed the needed O2 in the sep funnel. This meant I was only diluting the reaction with more air and slowing the next reaction down

2NO2 => N2O4

The rate of dimerization is proportional to concentration.
So I turned off the secondary air inlet and noticed the colour became darker. Edit- sorry, that makes it sound like the N2O4 is the darker product... it's just there was more NO2 by volume and hence darker.

[Edited on 26-12-2016 by Chemetix]

[Edited on 26-12-2016 by Chemetix]
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[*] posted on 27-12-2016 at 04:37


Do you have any idea if some of the ammonia is able to pass the reactor unreacted? That would result in acid containing dissolved ammonia nitrate.



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[*] posted on 27-12-2016 at 09:18
New Catalyst


Quote: Originally posted by phlogiston  
Do you have any idea if some of the ammonia is able to pass the reactor unreacted? That would result in acid containing dissolved ammonia nitrate.


In the preliminary trials I did with the catalyst on glass fiber, the support melted and there was little surface area to react with and ammonia started coming over past the reaction zone. White fumes appeared as the acid and base began to react.

This happened again today as I had made some modifications to the set up.
I dried the ammonia/air mixture with a reflux condenser this time and noticed there was more glow coming from the reactor and then things started to change. The oxidation chamber lost colour and there was no condensation forming. I lifted the condenser coil out and whiffed the emanating fumes lightly - ammonia. The catalyst had died.

I shut everything down and cleaned out the reactor; the support had a slightly glazed look and a greyish colour. There was oxide residue on the walls and I used some conc. HCL to remove it. What was telling and confusing was the smell of sulfide. Sulfur had killed the catalyst but where did it come from? It gave me the chance to try another variation I had in mind.

Pilot Ni.JPG - 316kB
Broken bath tile support and nickle oxide.

Pilot Ni Reactor sml.JPG - 209kB
Not only did the NiO work, it worked well. The reaction zone glowed much hotter and pulsed hotter with the higher flow rates from the air/ ammonia generator. I'd bet that this would self sustain once it has got to this temperature. Will try next run.

PilotReflux.JPG - 373kB
This is the condenser to dry the ammonia/air stream.
The pulsing glow happens due to the concentrated ammonia solution in the condenser falling back into the flask as drops, the cold concentrated solution emits gas as it hits the hot solution of urea.

The dried air/ammonia "burns" hotter than with the water rich vapour I was using. 1- it meant the high temperatures could have caused contaminants in the expanded clay balls to react with the catalyst or fuse with the catalyst, killing it.
2- it makes more concentrated acid without the introduction of water into the stream.

PilotConcentratedAcidFumesSml.JPG - 474kB
Concentrated nitric fumes like crazy in moist air. The oxidation chamber was filled with acid mist this time. Concentrated acid fumes can be seen leaving the absorption tower. I now understand the need for multiple towers used in industry.

I ran out of time to titrate the product, but it took more Bi-Carb to neutralise a similar quantity of the last batch, and the tower solution gave a more pronounced reaction with bicarb despite far less operating time.


[Edited on 27-12-2016 by Chemetix]
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[*] posted on 27-12-2016 at 15:09


POTENTIAL!
Looking great Chemetix, great work!

Have you tried MnO2 as the catalyst?
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[*] posted on 27-12-2016 at 15:31


Outstanding work, truly inspiring. Cobalt seems to be the ideal catalyst for this, from what I can tell it's in commercial use today. And a heck of a lot easier to get hold off than platinum/rhodium. If nickel was anywhere near this good, wouldn't we've heard about it by now?

Anyway, the biggest challenge as I see it is the ammonia-generation. I like your approach, but I still can't help thinking there's a better one out there. A kipp-style generator would be perfect, but that's not as easy as it sounds.
I'm not big on glassware, but I wonder if it isn't possible to construct a compact design from metal, at least the ammonia and reaction zones.




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[*] posted on 27-12-2016 at 15:59


My standard ammonia generator is NaOH drain cleaner and ammonium sulfate fertiliser. Neither is too expensive. I don't see why a different ammonia feed would be problematic.



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[*] posted on 27-12-2016 at 19:32


Quote: Originally posted by Fulmen  
If nickel was anywhere near this good, wouldn't we've heard about it by now?

.... but I wonder if it isn't possible to construct a compact design from metal, at least the ammonia and reaction zones.


It's funny, I've sort of made a career out of doing things that are assumed to be obvious to everyone else as either 'they've tried and it doesn't work' or 'if it worked like that they'd already be doing it that way'. Nickel seemed an obvious choice really; when you can't have Pt or Pd the next on the list is Ni.
But because of the German patent I tried cobalt first. Actually, I tried red iron oxide first and it didn't seem to do anything. The problem with these alternative catalysts is after shut down there is concentrated nitric acid around to basically chew off your catalyst in the reactor. Platinum puts up more of a fight in this regard.

And on to the other point, the glass porn. The short answer to 'is there a way to do it in metal' and I'd say yes. 316 Stainless would have to be the next best thing, I have this in my workshop and I'm handy with a TIG. But that said I might give a more grass roots approach a go too. Bits of copper tubing- glass bottles with holes ground into them- lots of teflon tape. Maybe I'll leave that to some inventive backyarder to complete, because it's entirely doable. The glassware gives a very educational approach to the process. You really can see what is happening and when and get a feel for how much. And I hope the pics are encouraging and informative for the forum.

I think the ammonia generator could have a few improvements made, I did a literature search for anything that can catalyze the urea decomposition reaction. Nothing useful so far, the research is focused around engine emission control measures. I found using glycerol or sugar with water I can raise the temperature and the rate of evolution...and the energy cost of generating it. I like the idea of just pour in the urea and water and no by products if you keep the ratios right.

I'll draw up a schematic using my M.S.paint- 'Fu'; I should get a better sketch app one day...

ps "Have you tried MnO2 as the catalyst?"

Het spijt me, ik weet niet dat die MnO2 werken. I should think it would work, I'm starting to suspect my suspicions about there being many available catalysts is correct.
Someone can give it a go.

[Edited on 28-12-2016 by Chemetix]

[Edited on 28-12-2016 by Chemetix]
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[*] posted on 28-12-2016 at 04:32


I absolutely love the "let me prove everyone wrong" mindset. Especially in this case !
How many pages in this forum alone saying this or that process for making HNO3 is not doable ?

The only sad thing I see here is the timing. A few more days and you would have definitely gotten my vote for Mad Scientist of the year :)
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[*] posted on 28-12-2016 at 04:47


Quote: Originally posted by Chemetix  
The problem with these alternative catalysts is after shut down there is concentrated nitric acid around to basically chew off your catalyst in the reactor.

Good point. Shouldn't be hard to avoid as long as one is aware of the problem though.

As for metals I agree that 316 is the obvious choice, it should work for the absorption tower as well as long as the concentration and temperature isn't too high. Copper sounds like a poor choice, it could perhaps work for the reaction chamber assuming you can produce dry ammonia gas?




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[*] posted on 28-12-2016 at 05:58


Mixing in some Dutch, love it Chemetix!
I look forward to seeing more, especially the Titration results.
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[*] posted on 28-12-2016 at 08:31


I missed your post where you tested nickel, seems like we have several catalysts at our disposal. This simplifies thing even more as I already have nickel salts. As for the ammonia-generator it's hard to beat urea as a source, although a kipp-style generator would be nice.
This might be useful: http://eel.ecsdl.org/content/4/10/E5.full (Electrochemically Induced Conversion of Urea to Ammonia)

It might be possible to design a pressure regulated generator this way, using a gravity fed reservoir and back pressure to regulate the electrode area.

[Edited on 28-12-16 by Fulmen]

Attachment: ECS Electrochem. Lett.-2015-Lu-E5-7.pdf (287kB)
This file has been downloaded 23 times





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[*] posted on 28-12-2016 at 09:45


Quote: Originally posted by Herr Haber  


The only sad thing I see here is the timing. A few more days and you would have definitely gotten my vote for Mad Scientist of the year :)


Yes, this is the most exciting project since Pok's making of Potassium. On an importance scale this has to rank very high.

Urea seems a very good source of ammonia: compact, dry solid, just add water and heat - what could be easier. Regulation would be nice - I guess that's what a Kipp would give you. Does the CO2 cause any problems other than dilution?

Also, urea is dirt cheap. I bought a 50 lb bag for $10.






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[*] posted on 28-12-2016 at 09:48


Quote: Originally posted by Magpie  
Quote: Originally posted by Herr Haber  



Also, urea is dirt cheap. I bought a 50 lb bag for $10.




Where did you find such deals?
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[*] posted on 28-12-2016 at 09:55


"Weed & feed" places. That is, agriculture and garden suppliers.



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[*] posted on 28-12-2016 at 12:41


did you try to use copper wire as catalyst?
I found some videos showing that it works fine
plz check attachment.

Attachment: Media.mpg (3.2MB)
This file has been downloaded 26 times

[Edited on 28-12-2016 by ecos]
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[*] posted on 28-12-2016 at 13:46


So what's the longest period of time that you've used a particular catalyst? Or how much product can you currently obtain before needing to change out the catalyst?

I'm the type of person that likes to do chemical reactions in stages, so naturally I'd suggest making some dry ammonia gas ahead of time and storing it in a bag, a "gas bag", if you will. I'm not describing the mother-in-law after a chili cook-off, but rather a plastic bag with a weight on top, to regulate the flow of gas. Even if it isn't used for bulk storage, some kind of bag like this can work as a regulator, to absorb pressure fluctuations from your ammonia generator. Air can be supplied the way you already do. Perhaps I could demonstrate it if I have extra time. But then again, if I had spare time, I might spend it taking rides on the pet unicorn that I'll never have either. But I can try.

A cubic foot of gas would be around a mole of ammonia, and that would make quite a bit of nitric acid, if system-wide efficiencies are good.




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[*] posted on 28-12-2016 at 13:48


Quote: Originally posted by ecos  
did you try to use copper wire as catalyst?
I found some videos showing that it works fine



You did see my original setup with copper...in your thread.

https://www.sciencemadness.org/whisper/viewthread.php?tid=68...

and your reply :

Quote:

I am really surprised that copper works as a catalyst . I thought we need only Pt to oxidize ammonia.i found a link that shows copper as a catalyst . it also has videos.Link :http://www.digipac.ca/chemical/mtom/contents/chapter3/fritzh...http://www.digipac.ca/chemical/mtom/contents/chapter3/fritzh...[Edited on 9-11-2016 by ecos]


And it works too well and over-oxidises the ammonia to N2 and H2O if you recall my original assessment.

CopperNH3oxidation.png - 165kB
copper glows alright- just no discernable production of NO or NO2.
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[*] posted on 28-12-2016 at 15:40


The copper is too active, does this mean that the Ammonia gets converted to N2 and H2O immediately or does it go to NO first and then N2 and H2O?
If its the second, higher flow rates could take care of this problem, I presume.
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[*] posted on 28-12-2016 at 15:40


Electrochemical urea to ammonia (eU2A) sounds like a promising alternative. The paper used nickel electrodes which had a catalytic function, luckily nickel strip for battery assembly is easy to get hold of. The method used constant voltage; 1.65V applied to 30% urea + KOH.



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[*] posted on 29-12-2016 at 00:43


As to the question of whether the ammonia goes to NO then N2, it is largely academic. I can't say by observation alone. I'll leave that to analytical chemists to solve one day.
But there just hasn't been enough time in the day for me to give the unit a good run down the highway so to speak, open her up and see what she can do.
Holidays have consumed me with family duties and finishing off commercial work as well.
Why won't someone pay me to be a hobby chemist? Dammit!

So as yet I haven't been able to get an estimation of catalyst life expectancy. All I can say is the cobalt carbonate survived several shutdown and restarts until a change in the system design ultimately caused it to die. Maybe using those clay balls was fine so long as there was moisture in the stream to prevent the catalyst being poisoned somehow.
Maybe the ceramic tile fragments are cleaner and will run at higher temperatures and drier conditions and would have allowed the cobalt to survive longer.
But I'm sure you can all appreciate that the goal is to find a set of parameters that allow the production of the highest volume with the highest concentrations in the shortest amount of time. I'll get a few days soon to let it have a good run and get an estimation of efficiency and final concentrations.

eU2A does sound like a faster way to get ammonia, but then, so is a bigger pot. The latter is the simpler approach, I'll leave electrochemistry for those braver than me.
The gas bag idea sounds a great way to do analytical studies on the reaction. I have my chemical engineering hat on at the moment, it's all about increase of production for minimum costs.

[Edited on 29-12-2016 by Chemetix]
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