Sciencemadness Discussion Board

ETN synthesis without H2SO4

Mikhail01 - 29-12-2019 at 13:22

Have any of you tried nitrating erythritol with only 100% HNO3?
Some nitrations have to be performed without H2SO4, such as RDX... and as far as i know it is possible to nitrate certain polyols like mannitol, glycerine with great yield (using only WFNA)... can the same be applied to erythritol, and if so, do any of you have some experience or a synthesis?

Pyro_cat - 30-12-2019 at 19:51

From what I have read I think I remember that the H2SO4 is needed to pull out the water.

Is 100% nitric acid is that even possible outside a high end lab ?

Distilling nitric is not something I have experimented with yet.

See what happens if I get back into mastering nitrocellulose.

Vosoryx - 30-12-2019 at 19:57

if you can get WFNA. but i cant think of a way to WFNA without using H2SO4 in the first place.

Mikhail01 - 31-12-2019 at 15:11

Quote: Originally posted by Pyro_cat  
From what I have read I think I remember that the H2SO4 is needed to pull out the water.

Is 100% nitric acid is that even possible outside a high end lab ?

You can distill the weak nitric acid to pretty close to 100% with the help of some concentrated H2SO4. I think you could make RDX even with less than 99% concentrated nitric acid but with great loss of yield...
Quote: Originally posted by Vosoryx  
if you can get WFNA. but i cant think of a way to WFNA without using H2SO4 in the first place.

Yes, the whole process has to involve H2SO4 either directly or indirectly, i was just curious about if someone has ever tried synthesizing ETN with only WFNA, i was curious about the possible yields...

I don't really want this thread to turn into an argument about costs or ease of acquiring reagents. Yes, i know you can obtain sulfuric acid relatively easily nowadays, but i'd like to add that even though you need H2SO4 to distill the weak HNO3 you can recycle it (with a bit of loss of sulfuric acid) so in the end, if one had a cheap source of HNO3 (Birkeland-Eyde process comes to mind, which might be even cheaper than buying actual lab grade HNO3 for some people, although time consuming-) and a proper distillation apparatus you could -almost- forget about the valuable sulfuric acid. It should be noted that sulfuric acid will likely be forbidden or strictly regulated in coming years, specially in the EU, and making nitric acid is easier than making sulfuric acid (you only need air, water and energy).

Looks like no one has tried it, so i will probably do it myself in the not so far future and report back, for the sake of it.

[Edited on 31-12-2019 by Mikhail01]

underground - 31-12-2019 at 16:24

It is actually working. I have seen a patent (don't remember which one exactly) that PETN has been made with FNA with almost 100% yields, so i am pretty sure it is working for ETN too. I would though make PETN or RDX with FNA.

[Edited on 1-1-2020 by underground]

Microtek - 2-1-2020 at 05:22

Whenever I have made PETN, I have always used WFNA (and no sulfuric). The yields are better, and the product is easier to purify (and it is more economical since the sulfuric that was used to concentrate the nitric in the first place can be reconcentrated and reused indefinitely). I'm sure that a similar process could be used for ETN.
Nitric acid can be concentrated using Mg(NO3)2 instead of sulfuric for breaking the azeotrope, though I don't think it is practical on the lab scale.

Yamato71 - 30-1-2021 at 20:45

33 ml of WFNA will esterify 10 g of pentaerythritol with excellent yields without the need for SA. It has been decades, but IIRC, PETN yields were consistently in the 20+ gram range. I assume that this works because nitric acid forms a 68/32% azeotrope with water. !00% nitric acid sequesters the water produced by the esterification just as sulfuric acid would, driving the reaction forward, until the acid concentration reaches 68%. This method has the added advantage of producing far less heat since SA isn't being hydrated.

Fyndium - 31-1-2021 at 06:44

The economics favor the use of pure nitric acid instead of double acid, and apparently it gives also favorable yields.

The HNO3 can be generated without sulfuric acid. The sulfuric acid used to dehydrate and distill WFNA can be regenerated with effort. Nurdrage experimented if some nitrate salts can be used as dehydrating agents.

Has anyone got synthesis description on their WFNA nitration process for ETN/PETN with observations about the process kinetics? Microtek?

fredsci93 - 23-3-2021 at 21:40

Not to be discouraging, I understand the reasoning for using FNA instead of sulphuric/AN however ETN yields via this (AN/H2SO4) process for me have been >~95% after purification, so even if it is more economical it cannot be any better than the conventional method, that being said ETN is an easy compound so I would not be surprised if FNA (yellow or white) would give yields ~95%. Just wanted to defend the current method as it's already perfect in my eyes :D

[Edited on 24-3-2021 by fredsci93]

Etanol - 24-3-2021 at 11:57

Quote: Originally posted by Microtek  

Nitric acid can be concentrated using Mg(NO3)2 instead of sulfuric for breaking the azeotrope, though I don't think it is practical on the lab scale.

It is work. I prepared 92% HNO3 with Mg(NO3)2*H2O and 86% HNO3 with Ca(NO3)2 from 70% HNO3. Concentration is of more 95% after the second distillation.

DennyDevHE77 - 17-8-2023 at 22:41

Quote: Originally posted by fredsci93  
Not to be discouraging, I understand the reasoning for using FNA instead of sulphuric/AN however ETN yields via this (AN/H2SO4) process for me have been >~95% after purification, so even if it is more economical it cannot be any better than the conventional method, that being said ETN is an easy compound so I would not be surprised if FNA (yellow or white) would give yields ~95%. Just wanted to defend the current method as it's already perfect in my eyes :D

[Edited on 24-3-2021 by fredsci93]


With which ratios of starting reagents did you achieve 95% yield?

With the most popular ratios AN/H2SO4/Erythritol (200g/300ml/60g) as well as with NaNO3/H2SO4/Erythritol (175g/300ml/60g) my yield reached 75g and 86g respectively (50% and 58%) when nitrating for two hours. This is extremely disadvantageous, because with the same 300 ml of sulfuric acid I get ~345g (~92%) of PETN.

Lately I even think to boil the mixture of nitrate and sulfuric acid under the reverse refrigerator to get a reaction mass with completely reacted nitrate, and maximally anhydrous nitric acid.


[Edited on 18-8-2023 by DennyDevHE77]

Microtek - 18-8-2023 at 01:22

IMO, the advantage of nitrating with only highly concentrated HNO3 (95+ %) is that you avoid sulfuric acid in the product. HNO3 in the product is not nearly as much of a problem because it is much easier to remove (in part because it is much more volatile, but it also seems that it is easier to wash out traces of nitric than traces of sulfuric).

Regarding AN in nitrations, I think I remember reading somewhere, that there is an intermediate equilibrium with formation of other species such as nitramide when AN is dissolved in H2SO4. It may well be that heating the mix can speed up the conversion to ammonium sulfate and HNO3. Just remember to cool it back down before the nitration...

[Edited on 18-8-2023 by Microtek]