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Author: Subject: Ostwald style nitric production
j_sum1
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[*] posted on 2-1-2017 at 05:05


Quote: Originally posted by Fulmen  


That's understandable, you have more than enough to deal with at the moment. Still, for a plant capable of producing practical amounts of acid a better method for ammonia is needed. Perhaps someone else could start experimenting with the eU2A, by the time they have a working method I'm sure you've made headway with the catalyst.

What is wrong with the standard ammonia salt and sodium hydroxide?




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Fulmen
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[*] posted on 2-1-2017 at 07:42


Nothing, but it will consume more chemicals. Urea is both cheap and readily available, and the CO2 doesn't seem to cause any problems.



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[*] posted on 2-1-2017 at 12:08


I alluded earlier to how I like doing experiments in stages. There's a practical reason for that. I think this project has a good start and a lot of potential, but it's possible that too many variables are being tackled at once.

Many people here have made ammonia at one point or another. It's a pretty easy thing to do. That's not the important part of your process. What's important, is your use of alternative, cheaper, catalysts for the oxidation of ammonia to nitric oxide. The ammonia can come from many different sources, even a pressurized cylinder.

If you can store enough of it ahead of time to allow your system to reach steady-state operational conditions, you can make measurements of the ammonia/air mix and flow rate, residence time on the catalyst, and make a determination of the product (so many grams per hour, etc.). If the reactor is always ramping up or down, it's difficult to make these measurements.

The "gas-bag" referred to is just a Zip-Lock bag. The plastic on these is somewhat tough, much more so than a garbage bag or something, but it still has some elasticity. I connect to one by poking a small hole in the inflated bag, and inserting a slightly larger diameter glass tube, maybe a couple of inches in length. This glass tube is connected to some flexible tubing, and the glass tube is taped down to the bag, like a nurse tapes an IV to your arm, to keep it from moving around at the bag seal. Sometimes I'll have trouble with the seal, but usually the seal is a surprisingly good one. A few days ago I put one of these bags together, and floated it on water with a weight on top. It didn't appear to lose any volume overnight. Of course, something like this can't provide more than a fraction of a psi, but it's an easy way to store a gas and use it at some adjustable rate.




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Fulmen
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[*] posted on 2-1-2017 at 12:36


Quote: Originally posted by WGTR  
Many people here have made ammonia at one point or another. It's a pretty easy thing to do. That's not the important part of your process.

For this prototype I would have to agree, but if one wants to scale things up to a decent production volume this becomes a big issue.

Bringing it up at this time could be a distraction, but at the same time the work shows such promise it's impossible for people to stop thinking of improvements.




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[*] posted on 2-1-2017 at 12:57


I don't know about Australia but buying or filling a cylinder of NH3 in the US might well bring the DEA a knockin'.



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[*] posted on 3-1-2017 at 02:40


Ok, here's the details of the latest run.

Catalyst: 1.0gNiO on 10.8g house brick support, screened to pass 7.0mm square mesh and retained on 2.0mm square mesh. Used enough to make a 5cm reaction zone.
Run time: 5hrs.
Condensate collected: 13ml
Tower collection: 15ml

Titrations:
titrated against 0.5M NaOH
1.00ml of sample in 10.0ml of demineralised water, 0.5ml of red cabbage indicator. (what else!)

Condensate: needed 12.6ml 0.5M NaOH to neutralise. Concentration of sample = 6.3M
Tower: needed 3.23ml 0.5M NaOH to neutralise. Concentration of sample = 1.6M
reference sample of commercial 70% HNO3: needed 33.5ml 0.5M NaOH to neutralise. Concentration of sample = 16.7M
NiRun4TitrationStart.JPG - 288kB Start of titration

NiRun4TitrationEnd.JPG - 222kB End point

As expected, but not what I hoped; its pretty mild stuff coming from the process. But not too far from industrial results- I think older style plants would get 30-40% from the oxidising chamber.

The visual observations of the oxidising chamber have been noteworthy. Each reaction has so far behaved differently, subtle differences and not so subtle.


NiRun4RxnZn.JPG - 718kB
Note the reaction zone, no pronounced glow like the first run using nickel
https://www.sciencemadness.org/whisper/viewthread.php?tid=71...


NiRun4Obs.JPG - 356kB
And not the dense fumes. Condensation appears more prominent but what does it mean? I will have to do some yield calculations next to see the sort of efficiencies the catalysts are displaying.

The results are not terrible. This was going to be difficult to get a result and I have come further than I expected with this project. I'm now intrigued by the possibility of making different catalysts, with promoter and activator additives. Also I want to try palladium just to see the difference between transition metals and a PGM. But increasing the ammonia to get a decent flow rate, and one that can be measured and controlled, will solve the issue of catalyst efficiency and conversion values.
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[*] posted on 3-1-2017 at 03:02


Do you have any idea/guess of how much ammonia was produced/consumed? From what I can tell you've collected appr 0.1moles of nitric acid.



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[*] posted on 3-1-2017 at 03:16


All I can say about the ammonia production is that it is slow. Just by looking at the fumes that enter the chamber it's a wisp of a flow rate. So really, the conversion might be moderate. More work to do.
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[*] posted on 3-1-2017 at 03:28


Luckily there are many ways to measure gas production, I would probably focus on that next. Sooner or later you will need some efficiency data.



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[*] posted on 3-1-2017 at 06:54


I'm not sure when I can do this, or if I'll have the time at all, but I'd like to help design the metering on the input side of the reaction.

The idea is to use gas bags containing ammonia or air, and seal these bags inside of larger chambers/tubes. A bag would be connected to the outside world through a fitting in the outer chamber. Gas flow could be controlled by a second fitting in the chamber, that would apply slight air pressure to the chamber. This would force ammonia or air out of the bag, through the output port. A MEMS flow meter on the input port can measure gas flow, and this can be integrated with time to give gas volume. As long as the pressures are low in the system (fractions of a psi), I don't think much error would be added to the results. Except for the flow meters, everything else is a DIY construction project, and fairly cheap. Since the flow meter is separated from the gas mixture by a diaphragm, it doesn't have to tolerate anything other than air.

I thought of pre-mixing ammonia and air into one bag, as this would require only one flow meter. However, I'm not convinced this is a good idea (BOOM!). Figuring out the flow rates can give an idea of the residence times of the gas mixture on the catalyst as well as the optimum gas ratio, and then it will be possible to tailor these parameter for best results.

I appreciate the pictures and your efforts at describing the results, by the way. This is turning out to be a very interesting and informative project.




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[*] posted on 3-1-2017 at 07:09


I like the bag-in-bag design, starting from a known volume you really don't need a flow meter. As a first approximation you could simply fill bags of known volume using the same setup&power as your experiment.



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[*] posted on 3-1-2017 at 12:22


Here's a flowmeter that I occaisionally use for metering argon. You can sometimes pick these rotameters up fairly cheaply on eBay. This one reads in SCFH (standard cubic feet per hour).



rotameter.jpg - 107kB




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[*] posted on 3-1-2017 at 21:41


Here's a brief video (greatly sped up, of course) illustrating the rough concept of a bag-in-a-bottle. The Zip Lock bag acts like a flexible diaphragm, and isolates the gas from the air supply that's driving it. This allows changing the gas flow rate on the fly. There is less likelihood, also, of an ammonia release into the room if the bag breaks.

Attachment: gas_bag_in_a_flask.mp4 (4.1MB)
This file has been downloaded 139 times




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[*] posted on 4-1-2017 at 01:44


The bag in a flask is an awesome way to do it really, scaleable with ease. The urea water thermal decomposition is slow; my god it's slow. But as a feed stock you have to concede it's cheap and easily handled. With some collective problem solving the ammonia generator can be made cheaply and effectively I'm sure.

So how much ammonia was the generator producing per hour? Not a lot. Today I got the generator running, then bubbled the outlet into a volumetric flask with about 100ml of DM water. After an hour of running the ammonia was removed and switched off. The 200ml volumetric flask was made up to the 200ml mark and titrated against a known concentration of HCL.

The actual procedure was done by taking a 10.0ml aliquot of ammonia from the 200ml standard solution flask and titrating with 0.455M HCL.
0.455M just happened to be the concentration of a 50.0ml pipette of hardware store HCL added to a 1000ml volumetric flask and titrated with the same 0.5M NaOH solution I used yesterday to find it's actual concentration.

10.0ml of NH3 solution was added to a flask with the same indicator as yesterday (red cabbage) and then titrated with 0.455HCl. until a lightly acidic point was reached.
This was a source of error with the titration as NH4Cl is slightly acidic at low concentrations so the end point needs a judgement as to the point of neutralisation. I took it to a mauve rather than amethyst which is the pH7.0 point. A low concentration of NH4Cl hs a pH of around 5.


Note: have edited out the calculations until I get better data, I wasn't happy reporting speculation.


[Edited on 4-1-2017 by Chemetix]

[Edited on 4-1-2017 by Chemetix]
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[*] posted on 5-1-2017 at 00:57


Hi guy,

Very interesting post and i will try to built a similar setup


Here a proposition, why not use ammonium nitrate wich is like urea a pretty cheap fertilizer.

As far as i know it causing troubles to distill off nitric acid from sulfuric acid and ammonium nitrate but ....

for running the Ostwald process you can do

NH4NO3 + NaOH = NH3 + NaNO3 + H2O

and the ammount of NH3 passing threw the catalyst can be controled by the rate of addition of NaOH soln into saturated boiling NH4NO3 soln


after you can boiled the resulting solution to obtain NaNO3 wich can be mix with H2SO4 to make more HNO3

with this you only lost the NaOH from the fist step, some enery to boiled of the soln of NaNO3 and some sulfuric acid

very cheap chemicals ! doubled amounts of HNO3


Another think : Why not absorbate the gaz into some H2O2 for accelerate the oxydation of NOX gases ?

Wait for your comments ;)
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[*] posted on 5-1-2017 at 04:28


There is a problem with getting ammonium nitrate these days. In fact just about any nitrate is hard to come by without paperwork and expense. Many people on this site have thought about and tried different ways of making nitric acid without a nitrate salt probably for that exact reason. Ammonium sulfate is readily available to generate ammonia by use of hydroxide. Even urea and sodium hydroxide makes ammonia quite rapidly and effectively. But they are extra expenses and extra steps.

An ostwald style plant is a continuous process, a switch it on let it run kind of thing, so urea and water can be left to boil and decompose without having to check on it. A reaction with an ammonium salt has to be run and monitored as a batch process, and once generated you need to then find a way to add it in a controlled way to the reaction zone. Despite WGTRs ingenious bag in a flask technique, I'd rather avoid it if I can.

And you are right about using H2O2, it does maximise the absorption of NOx. I think that step will be one for getting the last bits of efficiency from the process, I'm concerned about getting the reaction running reliably and in moderate yield for a start. I have no idea how effective these alternative catalysts are in the broad sense. I've got a lot of research ahead. But I'm close to being able to state yields and operating conditions for a given catalyst.
I'll keep posting my progress for those interested in this process.



NH3 Flowmeter Sml.JPG - 330kBThis is a very sensitive flowmeter I put together from fish tank needle valves and some small irrigation fittings. The fluid is ammonium sulfate soln. and some food dye.

[Edited on 5-1-2017 by Chemetix]
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[*] posted on 5-1-2017 at 08:11


Good job on the flowmeter. As long as it doesn't change, relative measurements can be recorded from it. The calibration can be done later on.



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[*] posted on 8-1-2017 at 01:02


I think this reference shows some results of using Cu/CuO as a catalyst : http://pubman.mpdl.mpg.de/pubman/item/escidoc:741540/compone...

I point to table 1( row 3 col. 5)

[Edited on 8-1-2017 by ecos]
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[*] posted on 8-1-2017 at 02:43


An update on progress

I've learned a thing or two so to keep the flow of information going I'll give an update.
Run#5 Ni2O3 black nickel oxide
I have a flow meter decided to try the highest flow rates that will sustain the reaction.
I replaced the ammonia generator flask from a 250 ml to a 1L 1/2 filled, I cranked up the heat to the ammonia generator and had it refluxing quite adequately, this should be a maximum of NH3 supplied to the reactor. I ramped up the air flow and tried to see the most flow I could supply. A red colour and heavy fog persisted. As I brought up the air flow, there was a point where the red colour disappeared. After bringing the ammonia temperature back down and also the air supply, the reaction failed to start again. The catalyst had changed.

Ni2O3 after run4&5.JPG - 241kB
This looks to be NiCO3 and perhaps some NiOH. It fizzed with dilute acid.
Nickel is susceptible to being chemically changed

Run#6 tried a tile glaze that did nothing

Run#7 CoO black cobalt oxide
Started the reactor heater, turned on the NH3 generator turned on the air with manometer reading 40mm. A dark red gas began to appear at the outlet then as the ammonia generator began to reflux a fog appeared. Ran the system with air at 50mm for a few hours then shut down.

If the reaction was producing dark red gas without fog before reflux then the urea decomposition reaction might be generating too much ammonium carbamate when refluxing. This might be the source of the fog. Ammonium ions get through the catalyst zone unchanged?
I took some of the condensate and evaporated it in a beaker.

NH4 residueRun5.JPG - 436kB
Those long clear needles look familiar. It looks like ammonia is getting past in significant quantities when the urea water reaction is refluxing.

Run8CoO.JPG - 202kB
Run#8 CoO same as run 7
Cleared the condensate line and flask, refreshed the tower water.
Kept the air flow on 40mm to begin with and maintained the urea reaction below visible gas evolution, no bubbles. Dark red gas without fog in the oxidation chamber, the condensate flask and the vertical displacement tube, no visible fumes or red gas leaving the tower.
Left the unit run for 3 hrs.
Switched off the reactor but bubbled the ammonia generator into a 200ml volumetric flask with cold water for 1hr with the same air flow setting (50mm).

Noticed bubbling in the condensate flask.
This would have to be the reaction :
2NO2 + H20 -> HNO3 + NO

Attachment: NObubbles Run8 CoO.mp4 (1.4MB)
This file has been downloaded 169 times

Left the reaction to continue overnight.

Next day.
Collected 7ml of condensate and 18ml of tower absorption.

Titrated the samples
condensate 8.1M = 0.056n
tower 7.2M = 0.122n
Ammonia generator collected 0.4M x 0.200L = 0.08n.hr-1
3 hrs @ 0.08n.hr-1 = .24n (NH3)

Theoretical amount of HNO3 from NH3 is n(NH3).024 x 11/6 = 0.439n

Yield (0.056+0.122)/0.439 = 0.4
Approximately 40% from the theoretical amount.


My 80% estimate was ambitious. But urea is cheap, and the rest can be scaled.
I need to reproduce these results a few times before I'll call it properly.




Flow meter Calibration.bmp - 669kB
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[*] posted on 8-1-2017 at 03:05


Excellent find Ecos.
It does explain why copper is so erratic as a catalyst at atmospheric pressures, I could find no activity for NO conversion with the so called "copper" scourer I had at the time.
For a start I have no way of telling if the "copper" was pure.
Higher pressure suppresses the formation of the metal nitride which stops the catalyst working. Other metals which have active oxides but resist nitride formation would be good candidates to screen for this process.
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[*] posted on 8-1-2017 at 09:34


I like your flowmeter. I made a manometer just like it for delta P measurements when I was trying to see if I could use an old HVAC fan from my house for a fume hood. I also used it when trying to develop a venturi based air-mover. Neither of those experiments produced a suitable air-mover, however. The delta P vs airflow characteristics were not appropriate.

I'm surprised that your data plot is so linear.




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[*] posted on 8-1-2017 at 12:25


I'm kind of surprised too. For a start there is no zero, the fish tank valve had no off point, just a slow leak. And I didn't run it a full open either, that would push the fluid over. The secondary valve controls the scale as I'm sure you know. I set it at something that gave me a small readable flow and a decent flow at around full scale which was around 90mm height. Values where taken by the time taken to fill a 1L volumetric flask.

The plot could be logarithmic, however, excel fits a fairly convincing linear regression.

If the value for 5mm height turns out to be somewhere around 0.5 - 1.0ml.s-1 I think I'm looking at a logarithmic plot. Which I suspect would be the case given how these things work.
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[*] posted on 8-1-2017 at 13:41


I was wondering if some sillica gell dessicant could be used to capture low concentration NO2 effectively, for later release by heat and production of concentrated acid? make for effective use of H2O2 in a separate container, instead of dumping it in the whole system and hoping for use vs. decomp. It was mentioned in another thread previously. At the verry least it could be used as a pre-exhaust scrubber, but I don't recall if there was any issue with NH3 absorbtion.

Ill try to look for that info latr, when more time is available




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[*] posted on 27-1-2017 at 14:40


I have a hypothetical that I was curious about for the acid production side of this question.

Could pumping in a close to stoichemetric mixture (for NO2) of ozone and nitrogen increase yield?

It seems a simple water electrolysis system hooked into a decent ozone generator could give you a low pressure source of fairly pure oxygen if arranged correctly. Pure nitrogen is a harder question, but I figured I'd get the easy stuff out of the way first.

I'd also be interested to know how much more effective H2O2 makes the absorption process, since such an electrolysis device offers the option of preparing high test peroxide before hand as a feedstock for the acid.




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[*] posted on 27-1-2017 at 19:30


If you actually intend on keeping the nitrogen as nitrite/nitrate, lead dioxide is probably the best scrubber you can get easily. However, if you want to remove all the NOx fumes, I'd recommend sulfamic acid. For convenience, urea can do a decent job too.



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