simply RED - 12-11-2012 at 03:25
My question is, what is the storage stability of mixed AN NM Al. Let us assume that it is stored in airthight container and only minimal traces of
water are presented. What is the primary reaction of the mixture degradation or is the mixture stable and impossible to degrade? Is it possible that
Al reduces the nitrate ion in the presence of nitromethane?
Ral123 - 12-11-2012 at 09:08
I'd replace the Al with sugar/or something like that to zero OB in the end/, that way I'll only have to worry about the water absorption. They add Al
to AN/NM to sensitize it and so the two wont separate in layers at zero OB.
simply RED - 12-11-2012 at 22:38
Ral, this is off topic.
Anyway I am asking about the storage stability of the mixture and the possible reactions of its degradation. As it it known in the presence of water,
active metals reduce nitrate ions to nitrite and then ammonia. The process is quite exothermic and has lead to accidental ignition of pyrotechnic
mixtures in the presence of water. See attachment.
Is the analogous process, nitrate reduction by Al, possible in the presence of nitromethane instead of water? The literature (see Google) states that
H atom donor (I do not know the exact mechanism of these reactions, may be a proton donor) is
required to run the process. The activation energy of the process should be high as the CH3 protons of nitromethane are not easily given off as the
initially formed ion (-)CH2-NO2 is thermodynamically unstable, so the mixture should be at least to some extent stable?
[Edited on 13-11-2012 by simply RED]
AndersHoveland - 13-11-2012 at 01:00
Mixtures of Al and NH4NO3 are used in commercially in mining, and were used in some military applications. They usually add stabilizers to the mix (1%
boric acid for example). Probably the fact that there is fuel oil or glycol in the mix also helps prevent reaction. It is much more problematic to mix
Al with NH4NO3 when there is moisture. NH4NO3 can be somewhat corrosive because of its lower pH, but at the same time Al is more resistant to
corrosion than many other metals. Zinc, for example, is incompatible with NH4NO3, and such mixtures can easily start reacting on their own. The
particle size of the Al will also make an significant difference; smaller particle size is much more vulnerable to corrosion.
simply RED - 13-11-2012 at 01:38
Without water, with standard 44 micron spherical Al powder and nitrate - it will take tens of years for the alluminium to corrode, if it does at all.
So, water is the absolutely needful ingredient for the Al to corrode. Alcohols will corrode Al too, as they form stable R-O(-) ions, especially
methanol!
My question is: can nitromethane participate and increase the corrosion of alluminium in the presence of nitrate salt or it can not?
Can the next reaction take place:
NO3(-) + Al + CH3-NO2 = NH3 + Al3+ + (-)CH2-NO2 (Moles not adjusted)
Or the reaction/s of degradaion of the mixture have different mechanism.
[Edited on 13-11-2012 by simply RED]
AndersHoveland - 13-11-2012 at 13:32
Something else to consider is that nitromethane itself can be corrosive, as it has an aci-form tautomer that is slightly acidic.
A quick internet search seems to give conflicting information: some sources say that nitromethane can be stored in aluminum, others say that
nitromethane is corrosive to aluminum. In any case, I am sure the reaction, if there is any, is not very rapid, because NM boosted Al-AN compositions
have been fairly well investigated, I have never come across any remarks on chemical stability.
simply RED - 14-11-2012 at 00:07
Indeed. I know the mix has been stored for a month with no visible signs of decomposition. Nitromethane should not be corrosive to Al - as some
sources say that NM is transported in Al containers and (see Google) - mixtures of NANO Al and NM nave been tested. If it was corrosive it would eat
NANO Al in no time. Some sources and patents (see Google) even say that NM is anti-corrosion agent preventing Al to be attacked by diluted alcoholic
solutions and halogenated solvents (to be used in deodorants in 0.3% concentration as anti-corrosion agent). There is even an article testing
explosive properties of NM mixed with Al-Mg alloy. The reason it does not attack the Mg is another point towards stability.
[Edited on 14-11-2012 by simply RED]