paraformaldehyde

[stanfield]

I did a search about paraformaldehyde (for RDX production...) :
one guy said you must boil down formaldehyde to obtain paraformaldehyde and an another guy said he obtained nothing with this method...

so, is it possible to make paraformaldehyde (I would like a precise recipe with all steps plz)

see ya !

[deezs]

I know one method for "making" paraformaldehyde: let it stand for about 2-3 years. It works. http://theforum.virtualave.net/ubb/smilies/smile.gif

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"Don't belive anything, just because there is a good proverb for it."

"To avoid injury in a battle, watch them from the nearer hill."

[stanfield]

no shorter way ?

[Lagen]

Stanfield: You probably want to make RDX via the E-process, right? I must warn you! Don't even think of it without procuring some boron trifluoride first! Without it, it will NOT work (you can be sure, it's tried), and if you heat the mixture above 65°C, it might work, but not the way you would like! Look here (http://theforum.virtualave.net/ubb/Forum1/HTML/000115.html) for what can happen to you. In this case, the failure was probably because no BF3 was added, the guys on that thread failed to point that out.

Regarding the paraformaldehyde: Don't confuse true paraformaldehyde (also called trioxymethylene) with polyformal or with the sludge in formaldehyde bottles. The first is a trimer of formaldehyde, and is useful in some HE syntheses where the other two can't be used because of their poor solubility. The second one is a polymer (n=10-50), it is prepared commercially and it's the main ingredient in all those paraformaldehyde disinfectant things. The third one is a mixture of the two. In the E-process, any of the three can be used. But: It has to be bought, and it ends up being more expensive (even more so because of the BF3 costs) than using good old N-nitration process or K-process. Secondly, it is next to impossible to make at home. Industrially, it is prepared in vacuum from a formaldehyde solution. Boiling down formaldehyde is bullcrap. And even if you'd try waiting 1-4 years for your 20 grams of paraformaldehyde sludge in your formol bottle, it might not work at all if there are polymerisation inhibitors added.

[This message has been edited by Lagen (edited August 20, 2001).]

[stanfield]

It can't be made at home ??? Why megalomania make it in his labo ? ...

[Lagen]

The synthesis on Megalomania's site is for a polymer of acetaldehyde, a completely different thing. But still, if you managed to make paraformaldehyde at home, from formaldehyde solution, it is more expensive and difficult to get than the equivalent of hexamine (at least for me, I don't know about France).

[stanfield]

so, you think, the hexamine/HNO3 method is the best ? (about yield, price,...)

[Mr Cool]

Add 160 grams of anhydrous NH4NO3 for every 140 grams of C6H12N4, it will improve the yields of this otherwise fairly crappy method.

[stanfield]

You mean I need to put ammonium nirate in my hexamine before nitration ? Are you sure ? I never heard this anywhere... What are consequences about final RDX ?

see ya !

[Mr Cool]

You don't need to, but it helps.
Look:

C6H12N4 + 4 HNO3 --> C3H6N6O6 + 3 CH2O + NH4NO3

But if you add ammonium nitrate:

C6H12N4 + 4 HNO3 + 2 NH4NO3 --> 2 C3H6N6O6 + 6 H2O

Same amount of hexamine, double the amount of RDX. You won't actually get twice as much RDX, but it'll help.

[stanfield]

ok, but if I have 100 g of my hexa/nitrate, how much HNO3 do I need ?

thanx !

[Lagen]

For every 100g of hexamine, use 140g dry ammonium nitrate (Edit: 115g theoretically, but I find it useful to use some excess) and 570ml HNO3 98+%. For the procedure, follow the link in my post above, it's at the bottom in Mr Cool's post.

[This message has been edited by Lagen (edited August 21, 2001).]

[Rhadon]

From a reliable source I know that paraformaldehyde _is_ formed if formaldehyde stands for a longer time:
"If a formaldehyde solution stands for a certain time [or is induced into sulfuric acid], fine, critalline and colorless polyoxymethylenglycoles with the formula H–(O–CH2)n–OH will form (n=8-100). This is paraformaldehyde."
I had some problems with translating the text, what I wasn't sure about is between '[' and ']'.

[Mr Cool]

H2SO4 will speed up the polymerisation I believe.

[Lagen]

Yes, paraformaldehyde forms in formaldehyde bottles, and that is because of the pH change due to oxidation of formaldehyde to formic acid. But nowadays most formaldehyde solution has some methanol added to it, which gets oxidised instead (forming more formaldehyde) so there is no acidity change and the amount of paraformaldehyde formed is negligible. The polymer also tends to form at lower temperatures (below 20°C) so a common mistake in storing formaldehyde is to put it in the cellar with other stuff. I was thinking about various ways to remove/oxidise the methanol or to isolate paraformaldehyde from the comercially available solution (not for RDX, but for pentaerythritol synthesis) and eventually I gave up after I found a great source of pure paraformaldehyde for 2$/lb.

[Rhadon]

This sounds interesting... can you tell us more about this source (not where you exactly got it from)?

[Lagen]

Of course, here (http://www.lachema-nera.cz/katalog_pdf/chem_p.pdf) is the page of the manufacturer's catalogue referring to it. The company I get it from is a small one, selling chemicals and microscopy equipment. Based on the todays exchange rate the price would be USD 2.06/lb., only 3% higher than the equivalent of formaldehyde solution. At first I couldn't believe it, too.

[Rhadon]

Thanks for this one, Lagen, it'll surely help me!

[10fingers]

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[This message has been edited by 10fingers (edited October 25, 2001).]

[Lagen]

From 100g hexamine I would get 316.88g RDX in theory, practically I get 180-210g with the ratios I gave. I know there is this strange figure in the Urbanski book, but I don't know anybody using such ratios. I think eventually everyone (well at least me and Mr Cool, follow the link above to see his initial post) has come to the conclusion that using a slight stoichiometric excess of AN is enough for the batch-type-no-recycling process of the home manufacturer. I notice a lot of people here planning on "recycling" their nitric acid from the nitration mixtures. You won't see me doing anything like that... Only factories with on-line analytical systems can afford that. I am scared enough by the unstable nature of some of the nitrolysis byproducts. Some of them can explode even in solution! I better distill some more fresh nitric acid - which is inexpensive for me - and play it safe. After all, I have had my share of accidents! Every time I pour the spent nitrolysis mixture into a great excess of cold water, then add a kilo or so of sodium carbonate to it. And flush it down the drain with plenty of water, or when I can be bothered, take it out to the fields and dump it into the ground. (It's a great fertilizer, isn't it?) BTW, nitric acid is the best enamel cleaner I know of... And it won't damage the enamel like hydrochloric acid does. Now, more seriously... Back to the factory and the recycling of HNO3. I'd *guess* the purpose of the great excess of AN in the Urbanski formula is to enable the recycling of both HNO3 and AN. Note the sentence where he says "the waste acid, after filtering out the remanent RDX, is cooled down to -12°C. Ammonium-trinitrate (NH4NO3.2HNO3) crystallizes. This is separated in the centrifuge and recycled into the reactor." [Sorry for possible crappy language, I don't have the English version of the book.]

[Lagen]

Oh and I forgot to comment on the economy of the process... Yes it is a shit load of nitric acid. But hey, you get RDX, the military's beloved HE! It's just as good as HMX at similar densities... All in all I'm glad to have such a simple process for making such a good HE. For me it just means getting more H2SO4 and dirt cheap fertilizer. The time and energy is unimportant for me, I have automated the boiling and distillation process...
There is hardly any way to avoid the great excess of HNO3. Water is produced in the process. RDX, like any secondary nitramine, is incompatible with sulfuric acid, hence with any nitration mixture containing it (designed to absorb the resulting water). At lower densities, the nitrating and esterificating properties of HNO3 are lost, oxidation processes prevail. To keep the concentration above 80% throughout the process, the initial conc. must be as high as possible and unfortunately, the great excess of HNO3 must be used. I should imagine one could use a mixture of a metal nitrate and acetic anhydride, but that doesn't help too much...
Regarding PETN, yes, convenient process, if you can get hold of PE! Making it, especially making the acetaldehyde for the synth, is a pain in the ass. And storing it is difficult, given its b.p. of 21°C.

[Mr Cool]

You could polymerise it to paraldehyde or metaldehyde.
But RDX is probably easier. For some reason I like it more too. Personally I use probably too much hexamine compared to the amount of HNO3, to make sure that the acid is used to its full potential. I don't care if I waste hexamine.

P.S. - I think someone was asking earlier about the order of adding the hexamine and AN. Well I add all the AN first.

[This message has been edited by Mr Cool (edited August 25, 2001).]

[10fingers]

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[This message has been edited by 10fingers (edited October 25, 2001).]

[Lagen]

The problem is that distilling the nitric acid (Edit: the way people here want to do it) is the point at which the mixture might decide to explode. It's not because of RDX, there are lots of various byproducts (linear, branched and polycyclic nitro compounds - see Urbanski) which are super sensitive. I don't know any convenient method of removing or decomposing them. What you describe seems to me as if they created a solution of AN in nitric acid having such a concentration that it can be plugged into the reaction mixture again. Obviously the main purpose is to extract the two moles of nitric acid and absorb them in the crystalline "trinitrate", which can be separated.
Regarding the chems prices: I am not surprised by the high cost of OTC 99% nitric acid. In Europe it is impossible to get, or the price is even more prohibitive. The highest conc. sold here is something like 65-70%. I must also straighten out one thing: The prices are different in Western and Eastern Europe. I quote the eastern prices, most of the European members on this board probably get the higher West European prices which are more close to the American niveau.

[This message has been edited by Lagen (edited August 25, 2001).]

[Tony Montana]

Lagen, could you treat your waste HNO3 with H2SO4 and CH2CL2? H2SO4 would dehydrate the HNO3, and the CH2CL2 would then absorb the now anhydrous HNO3 and repel the H2O/H2SO4. Using an eyedropper you could then extract the CH2CL2/HNO3 layer, then distilling that at around 40*C. The CH2CL2 would leave quickly, taking back any HNO3 that was wasted. Boiling the H2O off the H2SO4, would leave no waste at all. I have also dreamed of producing several batches of RDX using only, HNO3 and C6H12N4. Are there any distinct advantages with the addition of NH4NO3 as I have also never heard of this?? Also Lagen, you say you have automated most of the process, it would be great if you could tell us how you went about this, or even posting a few diagrams or pics would be much appreciated.

[Mr Cool]

Yes, adding NH4NO3 increases the yield, I'd say that this was an advantage.

[Lagen]

The core of the system is a temperature measuring station with 14 standard K-type thermocouple inputs and 2 duty-cycle inputs for measuring ambient temperature. Then theres a board with a 8055WD which controls the whole thing. One could think of it as a mirocontroller prototype board with many customised inputs/outputs, not an industrial type controller, because the industry mostly uses PGAs and PLCs (I hate them). Of course the watchdog is the most important part of the system! How it works: There is plenty of thermocouples you can attach at various points of the reaction apparatus. They range from -40 to 1000°C, can take most acids and if you really abuse them, they are cheap (3$). The accuracy is +-0.5°C ABSOLUTE over the whole range, and as with any thermocouple, the response is very fast. Either they are immersed in the reaction medium, or I attach them to glassware with a special heat-conducting paste. So I don't use mercury thermometers anymore... Other sensors I am using currently are primitive ones - water level, and the one I made for the nitric acid is a simple optics focusing green light from a LED and sensing it with a phototransistor, to detect acid dripping. Action members include a servo for valves, a few magnetic valves, power switches, a spark gap, and the most important "action member" - a panel with superbright LEDs to notify me when the thing is done. Then there's a manually switched temperature display on the measuring station. It is nothing very advanced, to do a particular job I change the whole program in the 8055. For boiling sulfuric acid you just need one temperature channel and a SSR/optotriac to switch the hotplate on/off. The program is simple - after the temperature rises to somewhere between 330-340°C and stays there for a few minutes, turn the hotplate off. Instead of the red light, a green one lights up, not unlike at a gas station. The point for me is that I don't need to babysit the apparatus and attend to it only when necessary. For nitric acid distillation, a heating mantle is too expensive for me (500-1000$) so I use a gas stove and a water bath. Three thermocouples are attached around the circumference of the distillation flask, another one goes into the flask from the top, another one is directly in the burner, and one is in the cooling bath of the receiving flask. The program tries to maintain proper temperature by turning the valve on the stove, if it gets really too hot the valve is stopped completely. After cooling down an ignition transformer (?) fires a series of sparks through the spark gap while the valve is being opened. Successful ignition is checked by the extra temperature sensing point (thermometer couldn't do it, right?) The regulation algorithm is nothing too sophisticated, it uses empirical constants which are related to the particular glassware setup. In the distant future I might improve it to solve differential equations http://theforum.virtualave.net/ubb/smilies/smile.gif so it could quickly adapt itself to the particular physical system but that's sci-fi at the moment. If the water level in the bath gets too low, a small magnetic valve lets in water from the mains. Similarly, if the temperature at the cooling flask gets too high, a valve replaces the bath with a cool one from the mains, the used water overflows to the drain. When the dripping stops for a preset period of time, the whole thing shuts down. Sorry, I don't have pictures and won't have them in the near future, as I don't have a digital camera.

[EventHorizon]

I'm sure there are plenty of people here with scanners that would be glad to receive some hard copies and scan and post them here for us all to see. http://theforum.virtualave.net/ubb/smilies/smile.gif

[Lagen]

OK if you are interested I will make a few pictures sometime this week and scan them at school over the weekend. I don't have much time as the college has already started for me and I must do (retry http://theforum.virtualave.net/ubb/smilies/frown.gif) 2 more exams.

[Lagen]

I just thought it might fit within the theme of this topic, as we mentioned the problems in storing acetaldehyde here... Today I visited a friend at a chemical research institute, the name of which I won't mention. I asked: "Do you have acetaldehyde here?" "Yes." "How do you store it?" She asked the other people: "The stuff that exploded in the fridge, was it acetaldehyde?" "No." So we had to find the people working with it, they just said "It's in the cabinet." I said "No, if it was in the cabinet it would have exploded!" (It was 30°C here today.) I made them find the bottles. And there it was, a happy Fluka bottle with acetaldehyde, the label just said "Store at 0-4°C" and there was an extra yellow-red label affixed saying "Warning! Internal pressure may be present!" I asked them "How do you open it?" "We just unscrew it slowly enough!" And I was like "Ohmigod!" but it looked like I was just picking up on them for details. And up to the present I haven't dared to ask for acetaldehyde at chem supplies shops because I didn't have a portable freezer box with me! So, what do you think, storing chemicals in ordinary bottles above their b.p. is OK?

[Tony Montana]

I have not had the pleasure of dealing with this nasty stuff, yet. But it does sound dangerous! I personnally would not take the risk of storing this chemical unless I was completely prepared. If I really needed it, I would purchase a bottle use what I needed and dispose of the rest, take it to a suitable place and put it in the sun and retreat to a safe distance. This would prove to be fun, and would give me valuble practical knowledge of how far you can actually push it.

[This message has been edited by Tony Montana (edited August 29, 2001).]

[stanfield]

My paraformaldehyde source is MERCK. Is this paraformaldehyde ready for RDX synthesis ? I don't understand your trifluoride problem... Megalomania dont talk about this stuff anywhere...

[Mr Cool]

Tony: that might be "fun", but it would spray toxic, irritating, flammable, carcinogenic, mutagenic acetaldehyde all over the place. Is that really a good idea? It'd be bettr I think to burn it if you want to get rid of it.
But why can't paraldehyde be used instead?

[stanfield]

So, Lagen (or anybody else...), could you explain to me the "trifluoride problem" ... ?

thanx...

[Mr Cool]

I believe BF3 is a catalyst which allows the cyclic structure to form.
I'm not totally sure though...

[stanfield]

Why Megalomania don't prevent/talk about this stuff ?

[stanfield]

Maybe, I have found a reseller for paraformaldehyde, it sells 1kg for 33$, is it a correct price ?

thanx...

[cutefix]

Boron trifluoride is a toxic gas, and would be difficult to incorporate it as a catalyst for home synthesis which is very effective for acetylation,alkylation,polymerization,condensation reaction.The most common liquid catalyst made from BF3, is boron trifluoride etherate;(C2H5)2BF3;made by vapor phase reaction of anhydrous ether and boron trifluoride.This is a reactive material and a fire hazard(due to presence of ether).There are other BF3 solutions such as alcohols,and acetic acid.I think the latter is suitable in replacing the difficult to handle BF3gas( in small scale/laboratory operation?).Besides the reacting medium contains acetic anhydride.So if the reaction needs 0.4% pure BF3 and these BF3 acetic acid complex contains 33%,then you can add 1.2% of the acetic acid/BF3 complex.For product details check this:
http://www.fishersci.ca/msds.nsf/96cb2019dad1311a85256670001d92b9/15fc8532ec01c0e4852566f1000366a5?OpenDocumentand for BF3 itself see this:
http://siri.uvm.edu/msds2/mf/cards/file/0231.html
I think the use of these catalyst is desirable only in industrial operation…