Sciencemadness Discussion Board

recrystallization PETN

berzelius75 - 9-5-2017 at 07:45

Hello and sorry for my approximate English.
I wish to synthesize PETN with HNO3 90% and H2SO4 98% and PE 99%.
I have a question more precisely on the recrystallization, I would like to carry out with 50% acetone and 50% ethanol (conc 95%)
The whole for use in a shapped charge, what is the duration according to you and the temperature of the solution to preserve to have better crystallization possible, the speed of addition in the cold water.
Thank you if anyone has precise information on this subject
thank you

Chisholm - 9-5-2017 at 10:01

What equipment do you have, and how much are you aiming to make?

berzelius75 - 9-5-2017 at 10:28

I have basic material for the moment, but convenient.
When has the quantity I would say approximately 100 gram.;)

Chisholm - 9-5-2017 at 14:18

It's best to keep the temperature below 60ºC for any nitric ester (PETN, MHN, NC, NG, EGDN, ETN, etc.) to help prevent decomposition.

The best procedure to use depends on whether you want large crystals or small crystals. If it's for a shaped charge, then you'll probably be dissolving the PETN again in order to add a binder or a plasticizer, so the initial crystal size doesn't matter.

For smaller crystals, just pour hot (roughly 55ºC) acetone-ethanol onto the crystals in small portions with stirring until the PETN has all dissolved, then add an equal amount of cold water all at once. A very fine, white precipitate of acid-free PETN should fall out of solution, and you can recover it with a filter. Add more water to the filtered liquid until no more precipitate appears, then filter again to recover roughly 98% of the PETN.

Elemental Phosphorus - 10-5-2017 at 15:02

If you want an exact procedure, it is really not hard to find a complete synthesis of PETN online.
The recrystallization is carried out using hot acetone, and the product is washed using sodium carbonate solution to remove acid, although this step may be unnecessary.

Here is a complete preparation: http://www.prepchem.com/synthesis-of-pentaerythritol-tetrani...

I would rather have small crystals than large crystals.

berzelius75 - 11-5-2017 at 10:21

Thank you very much, I have one last question concerning the distillation of HN03, I have a bottle of 1Lt of HN03 90% I wanted to know if by distilling it with H2S04 I could synthetically increase its concentration and purity or if it is waste I would like to try Rosco Bodine's method for PETN synthesis.
thank you

Elemental Phosphorus - 11-5-2017 at 13:08

Yes, you could distill your 90% nitric acid with 98% sulfuric acid to further increase its concentration, but why would you? The link I posted has 2 procedures, and your nitric acid is already concentrated enough to be used in the first one.

berzelius75 - 11-5-2017 at 16:57

Yes it is true, but I had a doubt I thought it needed at least a concentration of 95% HN03 for optimal performance.
I will try with this method, although it looks more complicated.
I am surprised even with a HN03 90% it is necessary to add 400 ML of H2S04 98% then rinse with H2SO4 50%.

But if this method is operational then I will try

I suppose the time of each step is almost identical to the other method?

thanks

PHILOU Zrealone - 12-5-2017 at 02:03

Quote: Originally posted by berzelius75  
Yes it is true, but I had a doubt I thought it needed at least a concentration of 95% HN03 for optimal performance.
I will try with this method, although it looks more complicated.
I am surprised even with a HN03 90% it is necessary to add 400 ML of H2S04 98% then rinse with H2SO4 50%.

But if this method is operational then I will try

I suppose the time of each step is almost identical to the other method?

thanks

The reaction is an esterification...as such it is an equilibrium reaction...so waters favors the hydrolysis...you have to catch the water from the inital reactants and from the reaction products because esterification yields water.
--> 1 mole per 1 mole of nitrate ester group (that is 18g/mole nitrate ester group)
R-OH + HONO2 --> R-ONO2 + H2O
If you have a tetrol then it is 4 times as much water produced for the entire molecule --> 72g/mole PETN

So the H2SO4 98% will take care of some of the water and push the equilibrium to the product side somewhat further.

The H2SO4 50% is just for the washing but it is factultative...you can simply wash with water with urea or a mild base (like NaHCO3/ CaCO3).

berzelius75 - 13-5-2017 at 05:29

Thank you for taking the time to detail.
Regarding the distillation of HNO3 90% the proportion with a H2SO4 96% in 50/50 seems to you correct?
200 ml HNO3 90% + 200ml H2SO4 96%?
thank you

PHILOU Zrealone - 13-5-2017 at 15:56

Quote: Originally posted by berzelius75  
Thank you for taking the time to detail.
Regarding the distillation of HNO3 90% the proportion with a H2SO4 96% in 50/50 seems to you correct?
200 ml HNO3 90% + 200ml H2SO4 96%?
thank you

Yes should be good to increase HNO3 concentration.

berzelius75 - 13-5-2017 at 17:16

merci PHILOU Zrealone