Rapid Nitration

[nbk2000]

It's occured to me that the limiting factor in the speed of most nitrations is the need to keep the reaction temperature below a certain point lest it go into a runaway reaction.

The usual way to prevent this is external cooling via ice bath, slow addition of reactants, and stirring. Well this is all fine and good...for the 19th century. :mad:

Jesus, we're still making NG the way it was made back when Nobel was fucking with it in the 1800s!

There's got to be a way to make a batch of NG (or TNP, or whatever) in a few minutes, rather than hours.

Well, while in Wal-Mart, I happened across some of those "ice cubes" that contain glycol inside of a plastic ball that you can use instead of regular ice so your drinks don't get diluted.

IDEA!

Fill a U tube with these polyethylene "ice" balls (frozen, of course) and proceed to add your mixed acid and glycerine in a continuous (but seperate) stream into one leg (The high one) and collect the product from the other (the low one).

See, the balls in tube presents a high surface area, but low volume enviroment for the reaction to take place. The balls get covered with the reaction mix, absorb the heat, and allow for a long dwell time for mixing of the reactants.

As you're constantly feeding in fresh "ice" in one leg, the used warm ones are pushed out to be recycled. The finished nitrated product is collected from a tap at the top of the "low" leg of the U.

The other idea was to use the usual "batch" process, but with the beaker filled with these "ice" balls. As the mixed acid is agitated by a constant air stream from the immersed plastic tubing connected to the aquarium air pump, glycerine is added in a stream from an immersed tube just above the aerator.

As the air bubbles rise through the "ice" balls, they carry the glycerine with them through the acid, and over the large surface area of the "ice" balls, rapidly giving up their heat.

As the nitration continues, the balls are scooped out in batches, to be replaced with fresh frozen ones. Eventually the NG collects in a layer at the bottom where it can be sucked up for purification.

[vulture]

Great idea, except for the fact that polyethylene is not resistant to oxidizing acids and thus not mixed acid, which is a very strong oxidizer.

[Marvin]

Another problem is that the lower the temperature you make the reaction mixture, the slower the nitration/esterification happens. Nobels equipment used cooling coils in the nitrators themselves, I dont think addition speed of the glycerol was the big problem so much as esterification and settling time. Mixed acid is just too slow if you wanted a much faster reaction you could use nitric anhydride, or NO2+ salts, but then things get expensive. I think most people would swap the extra speed for the lower cost and additional safety of mixed acid.

[vulture]

Nitric acid anhydride would even require more cooling since it is highly explosive at temperatures above -40°C.
I hope you meant nitric acid with an excess of N₂O₅ dissolved in it, because pure N₂O₅ with a flammable substance is certain explosion.

But still, the balls will dissolve by the action of the mixed acid.

[nbk2000]

Plastic companies make hollow teflon balls as well. Though you'd have to fill and seal them youself.

[ALENGOSVIG1]

Sounds like a good idea. Another thing i'd like to try is a jacketed 3 neck flask in a freezer fitted with an addition funnel. Blow air through it to mix, and pump ice water through the jacket. :p

Apparently a good freezer alone is sufficient to cool a nitro batch.

I was going to buy a jacketed 3L flask on a certain auction site but some bastard outbid me! :mad:

<small>[ November 13, 2002, 06:55 PM: Message edited by: ALENGOSVIG1 ]</small>

[nbk2000]

Even for just a normal nitration, your cooling "power" is limited by the surface area of your cooling surface. If you increase the cooling surface by 3 times, you've likely decreased your mixtures heat by a similar factor.

I wonder if dry ice would have any interaction with mixed acid? That'd certainly decrease a reaction temperature quickly, and you wouldn't have to worry about dissolving and mucking things up if it didn't interact.

[Arthis]

Hi. To avoid the problem with the plastic ball that may react in acid, it could be possible to cover them with some teflon tube that you close at both ends. You can even make your own balls, not to give your beautiful bucks to K-Mart.
I used to put the ice directly into the batch while making AP, as a little more water will not have much consequence on AP.
But care that your solution will refresh faster but you'll still have to add reactants slowly to avoid that the temperature rises.

But I don't know how to close teflon pipe.

[nbk2000]

I don't think teflon can be heat welded.

[stanfield]

haven't you got a picture of that ? I really don't see of what product you're speaking about... sometimes it's hard to understand when you're european :)

thanx !

[Arthis]

you don't understand about the teflon tube or about those "ice cubes" made of plastic ?

The first: <a href="http://www.interplastinc.com/stand.htm" target="_blank">http://www.interplastinc.com/stand.htm</a> there are'nt great photos, but I didn't found any other. This company seems to be specialized in those teflon (PTFE) tubes (extruded or not, balls...).

About the ice cubes, it's just water in a plastic sphere so that you can refresh your whisly without dilluting it. :D
You can imagine I guess ?
and I didn't find any photo. I really should buy a small digital camera to take all those useless pictures that are not worth a real camera (and you take as many as you want without paying the developpement (? is this the word ?) of the film.

About the topic, could we take a standard plastic ice cube, cover it with a small layer of teflon, the one use for sealing two pipes, then put it a PFTE tube, then another layer to have it sealed correctly. But it wouldn't be very efficient in cooling. Really I'm trying to find another method that would be easier, and more efficient.

<small>[ November 14, 2002, 12:45 PM: Message edited by: Arthis ]</small>

[stanfield]

ok, thanx ! :)

by the way, how do they cool the acid mixture in an explosive "enterprise" ? I guess they work with 200 Liter acid bath... this isn't a simple task to cool this and I guess too they don't use an ice bath ! :)

see ya.

<small>[ November 14, 2002, 02:40 PM: Message edited by: stanfield ]</small>

[Marvin]

vulture, Ive failed to find any references for nitric anhydride being explosive above -40C, or for that matter any references for it being explosive at all. If you have found some reliable references, I would like to see them please, as this obviosly makes a huge difference to its preparation and use as a reagent (usually in solution). The only reports of explosions associated with the oxide itself have been pure pressure explosions as a result of trying to keep it stable by sealing in glass containers, something that works very well for pure nitric acid. My older references state that the salt is stable at 8C in diffuse sunlight for over a month without noticable decomposition and that the solid and gas (no liquid state at normal pressure) are not explosive. Greenwood and earnshaw, which I consider a reliable modern refernce states only that it is 'thermodynamically unstable above room temperature'. It is an extremly active nitrating agent, and thus its not surprising that direct mixtures of the solid with certain organic substances, eg napthalene result in an explosion. Its heavily dissociated (NO2+ NO3-) in certain acids eg nitric, sulphuric, perchloric and this is a major route to nitronium salts, also providing for very rapid aromatic nitration. The solution in chloroform and carbon tetrachloride do not accelerate its decomposition, which suggests possible alternative esterification routes to me at least. Several references recommend its use as a nitrating agent, and somewhere I have some examples of its actual use. Possibly you are confusing this oxide with chlorine(VII) oxide or manganese(VII) oxide?

I'm not sure how rapid the action of mixed acid on polyethylene would be during NG manufacture. Its a long chain alkane, and if you keep the mixture low in nitrous acid/low temp, the right conditions for esterification rather than oxidation of the glycerol the mixture shouldnt attack the much less reactive PE at all. vulture is right in that its certainly a risk, and I wouldnt make the actual container from it, but PE containing frozen water would at worst dilute the reaction mixture if it goes oxisiding, something that would be formost on most peoples minds anyway. Glycol would be a real problem in the same situation, but since this isnt freezing I wouldnt expect it to be as good at removing heat from the reaction mixture either. The idea behind glycol mixturese is almost certainly to prevent fatigue in the plastic over many freeze/thaw cycles that would happen with water. The same freeze/thaw cycles unfortunatly that remove so much heat by enthalpy of freezing.

Teflon cold flows, so its likely it can be welded with pressure alone, a consequesce of poor intermolecular bonding I assume the tradeoff for extremely low reactivity and more obviosly of its 'non stick' properties.

[nbk2000]

Ah, but glycol DOES freeze...at something like -50. :D Thus you can get it VERY much colder than regular ice made from water.

Also, I don't think glycol leakage would be bad, assuming it didn't get too hot, since the product would be nitrated into EGDN, also an explosive. Whereas water would dilute the acid, making it ineffective.

<small>[ November 15, 2002, 04:51 AM: Message edited by: nbk2000 ]</small>