low.safety.standards
Harmless
Posts: 28
Registered: 17-7-2018
Member Is Offline
|
|
Water in my oxidizer!
Hello People,
I'm attempting to make a liquid fuel model rocket, I have my hands on a couple of hypergolic mixtures (Aniline / Turpentine + HNO3) and I'm facing
some issues with corrosion & water.
I'm doing NaNO3 + H2SO4 = HNO3 + Na2SO4 to get my RFNA and I wanted to convert to WFNA by leaving it out in the open so the NO2 can come out of
solution. Question is: How do I keep moisture from air from getting in my fuming HNO3 while allowing the NO2 to evaporate?
Also, I wanted to try liquefying NO2 to make dinitrogen tetroxide as it's far less corrosive than w/r fuming nitric acid (as long as it's N2O4, dry
liquefied NO2) so the question is: What can I use to dry the NO2 fumes before condensing them?
For people worried, I'm dripping aniline in RFNA outside with a full-face mask, face shield and fireproof gloves/apron, I also think it's dangerous
but a rocket at the small scale I want doesn't seem feasible without hypergolics.
|
|
|
Herr Haber
International Hazard
Posts: 1236
Registered: 29-1-2016
Member Is Offline
Mood: No Mood
|
|
You dont.
You can either bubble some dry & hot air (and maybe add a pinch of urea)
Or you can distill under vacuum.
You can also try to be super careful while distilling and not overshoot the temperature. It takes practice, a lot of time and a lot of ice.
|
|
|
low.safety.standards
Harmless
Posts: 28
Registered: 17-7-2018
Member Is Offline
|
|
I feared as much, will look into bubbling dry air with a heatgun or something. I took little care with the temperature... I see lots of tar on my
reaction, I think I distilled over some H2SO4 too, I'll improve my process and retry the acid.
About the tetroxide, are there no (readily available) drying agents for NO2 gas? I think passing through anything alkali would react but maybe silica?
How is the drying done industrially? Could I make a trap with H2SO4 and bubble the NO2 through it?
[Edited on 19-9-2018 by low.safety.standards]
|
|
|
MrHomeScientist
International Hazard
Posts: 1806
Registered: 24-10-2010
Location: Flerovium
Member Is Offline
Mood: No Mood
|
|
Concentrated sulfuric acid should work. I would also think calcium chloride (anhydrous) would be fine. That's easy to find as "Damp Rid" brand
moisture absorber in my area. Maybe even dehydrated Epsom salt would also work.
|
|
|
markx
National Hazard
Posts: 645
Registered: 7-8-2003
Location: Northern kingdom
Member Is Offline
Mood: Very Jolly
|
|
No direct need to heat the air that will be used to carry the nitrogen oxides out of the acid, but it sure needs to be dry. Use an efficient
desiccator stage in the air supply to get the moisture out or otherwise it shall collect in your acid and dilute it.
For practical purposes you do not need WFNA for a hypergolic fuel mixture...in fact the red stuff is preferred due to stronger oxydizing properties.
Soviet army used the red acid (melange) as rocket fuel component at a large scale and the old stockpiles are still corroding away the storage tanks in
some areas. It is a major pain to clean up these sites.
Exact science is a figment of imagination.......
|
|
|
macckone
International Hazard
Posts: 2159
Registered: 1-3-2013
Location: Over a mile high
Member Is Offline
Mood: Electrical
|
|
Dehydrated epsom salt is going to be best for drying NO2.
Calcium chloride will contaminate the stream with HCl.
You need a drying trap on your intake air if you are going to use the bubbler method for converting your red fuming to white fuming as markx pointed
out. For that calcium chloride is better.
|
|
|
low.safety.standards
Harmless
Posts: 28
Registered: 17-7-2018
Member Is Offline
|
|
I'll try it for drying my NO2, will make it out of my HNO3 and S to get back some H2SO4.
Quote: Originally posted by markx  | | For practical purposes you do not need WFNA for a hypergolic fuel mixture...in fact the red stuff is preferred due to stronger oxydizing properties.
|
It's more about testing safety, would rather play with WFNA than RFNA for development, I intend to use N2O4
for the final thing.
Can I throw some sulfuric acid in a magnesium milk bottle and dry it up in the oven? Any idea if the white goo they sell is pure or are there any
fillers/emulsifiers? Also, any advantages over bubbling NO2 through 98% H2SO4? (other than being able to recover/reuse the sulfate)
|
|
|
low.safety.standards
Harmless
Posts: 28
Registered: 17-7-2018
Member Is Offline
|
|
Going with lead nitrate
I'm making some lead nitrate, it can be easily dehydrated and decomposed and is a classic path to dry NO2 .
2 PB(NO3)2 = 2 PBO + 4 NO2 + O2
Trying HNO3 + NaF to make IRFNA too, got P4O10 to dry it.
Also found out my cat liter changes color with NO2
|
|
|
Tsjerk
International Hazard
Posts: 3022
Registered: 20-4-2005
Location: Netherlands
Member Is Offline
Mood: Mood
|
|
How do you dry your HNO3 with P4O10? Do you just put it in and distill? If that is the case you should be carefull as
it will also dehydrate HNO3 to N2O5, which is explosive by itself.
|
|
|
woelen
Super Administrator
Posts: 7977
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
Drying N2O4 with CaCl2 does not work. I have once tried that, but quite a large part of the NO2/N2O4 reacts with CaCl2 and one of the reaction
products is nitrosyl chloride (ONCl). You don't want that as contaminant in your NO2/N2O4.
|
|
|
hissingnoise
International Hazard
Posts: 3940
Registered: 26-12-2002
Member Is Offline
Mood: Pulverulescent!
|
|
| Quote: | | You don't want that as contaminant in your NO2/N2O |
And don't, whatever you do, accidentally introduce organic contaminants?
|
|
|
Microtek
National Hazard
Posts: 827
Registered: 23-9-2002
Member Is Offline
Mood: No Mood
|
|
I would be worried that using H2SO4 to dry NO2 would lead to nitrosylsulfuric acid, which may not contaminate the gas to any great extent, but would
likely reduce the yield.
|
|
|
WGTR
National Hazard
Posts: 971
Registered: 29-9-2013
Location: Online
Member Is Offline
Mood: Outline
|
|
Use only enough dried silica gel to remove the moisture that you think is present. The gel will quickly turn dark as it loads up with NO2,
but it has much greater affinity towards adsorbing water than it does NO2. A quick puff of dry oxygen will flush most of the
NO2 out of the gel, while many minutes of flowing dry air would be needed to remove moisture to the same extent. Some residual nitrogen
will likely be left behind in the silica gel as nitric acid, and this will be hard to remove completely even with heat.
|
|
|
low.safety.standards
Harmless
Posts: 28
Registered: 17-7-2018
Member Is Offline
|
|
| Quote: Originally posted by Microtek | | I would be worried that using H2SO4 to dry NO2 would lead to nitrosylsulfuric acid, which may not contaminate the gas to any great extent, but would
likely reduce the yield. |
| Quote: Originally posted by woelen | | Drying N2O4 with CaCl2 does not work. I have once tried that, but quite a large part of the NO2/N2O4 reacts with CaCl2 and one of the reaction
products is nitrosyl chloride (ONCl). You don't want that as contaminant in your NO2/N2O4. |
I was going with either H2SO4 or P4O10 as someone already mentioned the trouble with CaCl2 and
the orange nitrosyl chloride. For me it's easier/cheaper/safer to use P4O10 than using the 2:1 parts of
H2SO4 needed to dry HNO3, at some point I'll have to make some 4 liters of it.
| Quote: Originally posted by Tsjerk | | How do you dry your HNO3 with P4O10? Do you just put it in and distill? If that is the case you should be carefull as
it will also dehydrate HNO3 to N2O5, which is explosive by itself. |
Ah good tip! I was wondering why they didn't use N2O5 instead of HNO3 or N2O4. And yes, by what
I've read just throw it in and distill one from the other, I'll assume 5% water (based on measured density).
| Quote: Originally posted by WGTR | | Use only enough dried silica gel to remove the moisture that you think is present. The gel will quickly turn dark as it loads up with NO2,
but it has much greater affinity towards adsorbing water than it does NO2. A quick puff of dry oxygen will flush most of the
NO2 out of the gel, while many minutes of flowing dry air would be needed to remove moisture to the same extent. Some residual nitrogen
will likely be left behind in the silica gel as nitric acid, and this will be hard to remove completely even with heat. |
I might try putting some O2 through it and try getting it back. My actual thinking was to bake it and collect the gas!
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
