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Author: Subject: Hydrazine
Praxichys
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[*] posted on 7-10-2015 at 09:33
Progress report 1:


Improvements to GB1153483, in lieu of GB392845 on the manufacture of Hydrazine Sulfate: A Chlorourea-Ketazine Process not involving Cl2.

I decided to give GB1153483 a try, just to see whether their 75% claimed yield held any vestiges of truth.

12.6g (0.2 mol) urea was dissolved in 18.9g water. 1.6g of 50% NaOH (0.01 mol) was stirred in and the mixture was placed in the freezer.

When the mixture had dropped to -10C (it froze), 125g of 12.5% commercial NaClO (0.2 mol) at 0C was added in roughly 10ml portions evenly over an hour. Vigorous stirring and re-chilling followed each addition. The reaction is not very exothermic but any rise in temperature above 5C results in bubbling, undoubtedly signalling the decomposition of the chlorourea intermediate. The bubbling was most pronounced on the first and last additon, suggesting that thermal control is difficult with a low reaction mass, and decomposition of the intermediate is fast at high concentrations. The mixture does not foam.

After the last addition of NaClO, 30.4g of 50% NaOH (0.38 mol) with 0.1g Knox gelatin was added with rapid stirring, causing the light green mixture to begin foaming. The reaction was heated as quickly as possible, reaching 60C in about 10 minutes and causing foam to add another 1/3 to the volume of the reaction mix (total about 300ml incl. foam at peak). The color of the liquid gradually became orange/amber. After approximately a minute of exotherm the foam rapidly subsided, leaving a straw colored, foam-free, hot liquid characteristic of a hydrazine prep.

This was allowed to cool with stirring with a watch glass over the top of the erlenmeyer until it reached approximately 30C. 28.8g (0.4 mol) methyl ethyl ketone was added and the mixture was allowed to stir for an hour for the azine to form, cooling to room temperature in the process.

The azine layer was extracted and immediately run into 19.6g H2SO4 in 20.9g H2O at about 30C. Hydrazine sulfate precipitated immediately. This was stirred for 10 minutes, then heated with stirring for about 30 minutes to drive off the MEK. After a loss of 1/3 of its volume, the mixture was placed in the freezer and chilled to 0C. It was then vacuum filtered and washed twice with 30ml portions of ice water.

The dried filtrate weighed 6.26g, or 21% of theoretical yield, and consisted of dense, pearlescent crystals consistent with hydrazine sulfate.

Some notes:

-All percentages listed are w/w.
-Satuating the reaction mix with NaCl after extracting the azine (30g was added and did not fully dissolve) yielded no more extractable azine, after 24h.
-Theoretical yield would net a volumetric efficiency of 96g hydrazine sulfate per liter of flask volume, including room for foam. The 75% yield in the patent would net 72g/L, 50% would net 48g/L and the current yield was 20.9g/L. The "Mr Anonymous" method requires about 6 liters of volume for at max 236g of product, an efficiency of 39g/L. Achieving the same yield as Mr. Anonymous (ca. 60%) using this method would result in a volumetric efficiency 1.48 times greater. The yield stated in the patent would achieve 1.85x over the M.A. method - a marked improvement in both volumetric efficiency and safety, albeit with judicious temperature control.
- I prefer the ketazine extraction method over direct precipitation. I feel like M.A.'s method has a high level of Na2SO4 contamination.

Things to try on the next run:

- Spread out the addition of the NaClO. Ideally the mix should never rise over -5C. Use a bowl of 30% CaCl2/H2O chilled to -20C as a thermal buffer to surround the flask and absorb the heat. Regrettably, my lab freezer is too small to set up an addition funnel/stirrer inside, so additions are limited to small-volume aliquots.
- Make a schedule of additions starting and ending small, max 10ml.
Schedule, ml/5 min intervals, total 1h10m: 5, 5, 5, 10, 10, 10, 10, 10, 10, 10, 10, 5, 5, 5. A volumetric pipette stored in the freezer will help with this.
- Use fresh NaOCl. The commercial 12.5% has been in my freezer for a year. I went out and purchased 4 gallons of 10% today. The slightly lesser concentration of hypochlorite will also help with thermal management.
- Stir overnight with MEK to fully form the azine. Not sure about rate of reaction on this.
- Use 10% more MEK to make up for unwanted products formed with unreacted urea/hypochlorite in the basic environment.
- Use a separate gelatin solution rather than the NaOH solution. Gelatin clumping was a problem in the NaOH and its effectiveness as a chelator was probably compromised. I feel that this is a big factor, per US1959503(A)/GB392845. It may also significantly increase the foam volume, reducing volumetric efficiency to a point where this method will be inferior to others.

Failing this, I will try a third time with recrystallized urea. It's a pain in the ass to do, so that will be a last resort. I will also double the scale, and split the reaction mass into two equal portions prior to the hydrazine extraction. One will be azine-extracted and the other will be directly neutralized/precipitated with HCl/H2SO4, to check the efficiency of the azine process.

A possibly interesting experiment:

- What happens if all NaOH is added to urea to form essentially cold conc. ammonia first, then add hypochlorite slowly at -10C? What happens when this is done with MEK present in the ammonia?

[Edited on 8-10-2015 by Praxichys]




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[*] posted on 10-5-2016 at 09:38


Quote: Originally posted by vmelkon  
COPPER IS EVIL! Cu2+

Just for your info:

I redid this experiment --- the Nurdrage method : mix 2-butanone and ammonia solution. Then drip NaClO slowly.
The glassware in which I had my NaClO was contaminated by a copper compound.

My yield was 0%.
Definitely, the presents of Cu2+ messes it up.
------------------------
From
http://www.lookchem.com/Chempedia/Chemical-Technology/Inorga...

2 NH2Cl + N2H4 → N2 + 2 NH4Cl
This reaction is particularly catalyzed by copper. A large excess of ammonia and the addition of complexing agents such as ethylenediaminetetra-acetic acid (EDTA) are used as countermeasures.



lookchem.com is a business network from the Chinese government to earn more money from Western countries with their own asian companies. For professional business profiles only, NOT a website for chemists. Not a good source of information. ;)

The last post: ammonia dissolve better in cold water but what is the reaction mechanism between urea and sodium hydroxide, without hypochlorite ?...
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[*] posted on 17-5-2016 at 07:21


Praxichys - thanks, that is an interesting experiment.

We also tried a variant method from the literature (don't have the exact reference though) which involved bubbling Cl2 gas through a urea solution containing some dissolved gelatine in order to produce chlorourea. The chlorine was absorbed pretty well and a yellow coloured solution resulted. We tried to use about 1.1 x the stoichiometric amount of Cl2 gas needed.

The solution was fairly concentrated - about 30g of urea in 60ml of water, plus about 0.3g gelatine.

Then this was added to a chilled solution of sodium hydroxide (24g in 50ml deionised water). There was a STRONGLY exothermic reaction at this point (easily reached 90C without much difficulty) and some foaming.

Once this died down, HCl was then added until gas evolution stopped, at which point there was a crystalline white precipitate (we assume NaCl) which we filtered off.

The filtrate was then acidified with 50% sulfuric acid and chilled. We got some crystalline hydrazine sulfate, but not much, probably only a few grams.




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Rosco Bodine
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[*] posted on 17-5-2016 at 13:37


Quote: Originally posted by Praxichys  

I feel like M.A.'s method has a high level of Na2SO4 contamination.


Uh huh ....I see, you "feel" .....say what ? ! Hmmmph

Try the improved method with the bulk neutralization using HCl followed by the H2SO4 ....that was designed to soothe feelings :D

The interesting thing for followup would be the use of a manganese salt to increase yields as reported by Russians.
See these posts linked

http://www.sciencemadness.org/talk/viewthread.php?tid=1128&g...

http://www.sciencemadness.org/talk/viewthread.php?tid=1128&g...
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Praxichys
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[*] posted on 27-5-2016 at 05:32


Quote: Originally posted by Rosco Bodine  
Quote: Originally posted by Praxichys  

I feel like M.A.'s method has a high level of Na2SO4 contamination.


Uh huh ....I see, you "feel" .....say what ? ! Hmmmph

Try the improved method with the bulk neutralization using HCl followed by the H2SO4 ....that was designed to soothe feelings :D

I "feel" things when I can't be bothered to generate data. :D

I only have concerns about contamination because the solubility curves of the two suggest that they probably coprecipitate to some degree. Precipitating hydrazine sulfate from a sodium sulfate or even sodium chloride solution is going to warrant recrystallization at the least. I'd be curious to assay the hydrazine content of that, just to see. It would be virtually impossible to judge the purity of such a mixture by eye since the crystals can be made similarly dense and granular using the precipitation methods given.

The azine extraction method removes pretty much all ionic contaminants by nature. Granted, it does use more glass and has some toxic intermediates, but I'd rather do a L/L extraction over a recrystallization anyway. I do not doubt that your method is optimized for high yield - I just prefer to work it up differently out of concern for contamination.




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[*] posted on 27-5-2016 at 13:25


Also prefered the MEK-azine extraction, really brings peace of mind to know there are no contaminants in there! ;) Besides... during acid neutralization of the entire reaction mixture, the CO2 effervescence is really strong and creates an aerosol which will likely also contain some hydrazine. So this is not something that should be performed without safety measures IMO.
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[*] posted on 27-5-2016 at 20:10


Trace sodium chloride as a spectator ion is a pretty low concern in most reactions where the hydrazine sulfate would be later used. And there is a chance some of the hydrazine is sequestered as carbonate disrupted by acidification, which could benefit yield.
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[*] posted on 10-10-2016 at 08:02


Quote: Originally posted by Al Koholic  
The fumes smelled relatively ammoniacal but also had a distinct sweetish component. /rquote]
In my experience, N2H4 smelled of Ammonia mixed with woodsmoke.
Like a sweet mesquite BBQ undertone. Too bad it's so toxic. :(
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[*] posted on 19-4-2017 at 19:32


Hydrazine hydrate monohydrate is a reductive agent used as materials of medicine, pesticides, dyestuff, blowing agent, and photographic developer. It is a colorless, fuming and basic solution with a peculiar bad smell, soluble in water and alcohol, insoluble in chloroform and ethyl ether, flammable and corroding glass, rubber and leather, hydrazine hydrate's severe toxicity accumulates and harms blood and nerves. As an important raw material of Fine chemicals, hydrazine hydrate is mainly used as to synthesize the foaming agents AC, D1PA and TSH.
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[*] posted on 20-4-2017 at 10:13


Quote: Originally posted by Al Koholic  
As a matter of fact, I ran into exactly the same problems. The bubbling upon supposed neutralization of the hopefully hydrazine solution is most perplexing. I did not notice a green gas but more of a thick cloudy white vapor of some kind during my neutralization. I also used a somewhat large excess of NH3...

Lets think about this...I did not use gelatin or EDTA and still I get the bubbling upon warming of the solution and neutralization. You used both gelatin and EDTA and notice similar bubbling although noting the presence of chlorine by smell which I did not notice. Perhaps some side reactions are occuring in both of our cases with different outcomes? Seems unlikely...

Did you notice a really bad smell when you added the H2SO4 to the solution for neutralization? It was bad in the sense that rotting food is bad...nauseating...not like the pungent sting of Cl2.

[Edited on 3-12-2003 by Al Koholic]
The bleach could have chlorate prehaps. So the gas could be chlorine dioxide


[Edited on 20-4-2017 by The jersey rebel]
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