Sciencemadness Discussion Board

HClO4 from KClO4 and H2SO4

aquaregia - 9-5-2011 at 01:34

hello everyone,
Could you please tell me what is involved in HClO4 synthesis from potassium perchlorate and sulfuric acid? I would like to make some ammonium perchlorate for a small rocket engine. Since I have all the required glassware, condenser etc, I was thinking about distilling perchloric acid the same way I make concentrated HNO3...
then, I would react the HClO4 with NH4OH to make the ammonium perchlorate.
Needless to say, I want to be safe. I remember mixing some sodium chlorate with sulfuric acid as a kid, and Chlorine dioxide being what it is decomposed with a bang!
Anyone with experience in making HClO4, please advise?

symboom - 9-5-2011 at 01:50

a better reaction is
sodium perchlorate make sure there is no chlorate
NaClO4 + HCl → NaCl + HClO4 then add ammonia gas
this product should be very pure ammonium perchlorate precipitating out

ammonium salts with sodium perchlorate. This process exploits the fact that the solubility of NH4ClO4 is about 10% of that for sodium perchlorate

aquaregia - 9-5-2011 at 01:54

Thx,
but I only have some lab grade KClO4 not sodium....
but then, how do you separates NaCl from NH4ClO4 from solution in your reaction?

[Edited on 9-5-2011 by aquaregia]

oops, you answered that question already, sorry.
Say, would this work with potassium?

[Edited on 9-5-2011 by aquaregia]

Mixell - 9-5-2011 at 02:25

It will not work, the solubility of potassium perchlorate is very low in water:
0.76g/100ml at 0C.
2.56g/100ml at 20C.
and 22.3g/100ml at 100C.

symboom - 9-5-2011 at 02:57

oh forgot that you said potassium perchlorate youll have to make perchloric acid

woelen - 9-5-2011 at 03:18

Making HClO4 from KClO4 is quite dangerous. I understood from old text books that it can be made by reacting KClO4 and H2SO4 and distilling the nearly anhydrous acid at reduced pressure. The anhydrous acid, however, is extremely reactive and very dangerous to handle. Any organic or other easily reduced material may lead to explosions (e.g. think of vaseline or grease for sealing joints in the distillation setup). Even in the old pre-war textbooks the high risk of handling anhydrous perchloric acid is mentioned.

If all you want to do is make a rocket, then I would either try to find sodium perchlorate and use that for making ammonium perchlorate, as indicated above, or try a completely different composition for the rocket. I'm no expert on rocket engineering, but I'm quite sure that a google search on construction of rockets gives many alternatives for a composition based on ammonium perchlorate.

ItalianChemist - 9-5-2011 at 03:23

Add conc. sulphuric acid to a solution of barium perchlorate, barium sulphate precipitates out and HClO4 stands in solution. Don't use too much concentrated solution of barium perchlorate or it will explode ;)

woelen - 9-5-2011 at 03:33

I'm afraid this is of no help to the topic starter. Barium perchlorate is even harder to obtain than ammonium perchlorate. And if the goal is ammonium perchlorate, then there is no need to make HClO4 first. Simply adding a solution of ammonium sulfate to a stoichiometric amount of barium perchlorate does the job even better.

Btw, mixing a solution of barium perchlorate with sulphuric acid does not easily lead to explosion. The aqueous solution will not contain anhydrous non-ionized perchloric acid.

STOP!

aquaregia - 9-5-2011 at 03:43

and listen....
I HAVE POTASSIUM PERCHLORATE!
not barium, not, sodium, and not plutonium for that matter...
if Making perchloric acid from that product is dangerous, that is that.
I'll just have to use potassium perchlorate and R45M+catalyst in the engine (I am an expert in rockets). But the burn rate is high and unpredictable, hence the need for NH4ClO4.
is it not possible to displace the K+ ion for NH4+?

aquaregia - 9-5-2011 at 03:47

what happens if I mix ammonium sulphate to potassium perchlorate? would that work?
I am speaking out of my butt, no need to remind me!:P

ItalianChemist - 9-5-2011 at 03:59

Quote: Originally posted by aquaregia  
and listen....
I HAVE POTASSIUM PERCHLORATE!
not barium, not, sodium, and not plutonium for that matter...
if Making perchloric acid from that product is dangerous, that is that.
I'll just have to use potassium perchlorate and R45M+catalyst in the engine (I am an expert in rockets). But the burn rate is high and unpredictable, hence the need for NH4ClO4.
is it not possible to displace the K+ ion for NH4+?

Calm down....

aquaregia - 9-5-2011 at 04:05

I am calm!;)

Mixell - 9-5-2011 at 04:41

Displacing cation is usually done via solubility differences, and potassium perchlorate has a VERY low solubility compared to other perchlorate salts (only outmatched by rubidium), you not going to displace the potassium with anything, unless it is rubidium (and even here it's not practical, the differences are so small that they are negligible).

ItalianChemist - 9-5-2011 at 06:58

Quote: Originally posted by aquaregia  
I am calm!;)

I don't think so!

woelen - 9-5-2011 at 12:12

Forget about any displacement reaction if you only have KClO4. If you only have KClO4 then the only option is distillation of HClO4 from KClO4+H2SO4.

But if you are an expert on rocketry, then I expect that you will find other rocket compositions which work well and which can be made from chemicals available to you. If you can't, then please don't call yourself an expert ;)

aquaregia - 9-5-2011 at 22:50

Woelen,
please understand, that I have indeed experience in sucrose propellant as well as having tested various KClO4 propellants... And as I said, KClO4 has a very high pressure exponent meaning that burn rate is too much dependent on motor pressure (resulting all too often in CATO!). Which is why it would have been nice to use ammonium perchlorate.
Also AP has an higher Isp than KP as it produces more gas. Anyhow, this is outside the chemistry subject. I was expecting that the answer to my question would be no. Now just for my education, why is displacing HClO4 from its salt and H2SO4 so dangerous? Is it because the HClO4 spontaneously decompose into water and chlorine oxides/chlorine? Or, is it just because it is so strong an oxydizer that any organics will combust when in contact (as it has been mentionned above)? has anyone of you lot ever tried this experiment? I might be tempted to try the distillation using a 50 ml round flask on the distillation rig with full face shield and rubber suit...:D

woelen - 10-5-2011 at 00:37

I never tried the distillation myself, but I have read accounts of spontaneous very violent explosions. A small amount of organic matter, or a somewhat too hot spot may start a very violent reaction locally, which then quickly spreads out over the entire lot. So, the explosion will be violent and extremely exothermic decomposition of HClO4, which is triggered by some unhappy event in the flask.

I personally do not have the balls to do this distillation, but of course, if you have a blast shield (e.g. double walled pyrex glass between you and the distillation setup), and the ability to control the distillation from a distance from behind the shield, then you could give it a try. You then still have to handle the acid from nearby, when disassembling the apparatus and pouring the acid from the collecting flask.
A somewhat safer method may be to have some water already in the well-cooled collecting flask and let the anhydrous acid drip into the water. In this way, the acid slowly comes into the water in a controlled way and no anhydrous acid builds up. As long as the concentration remains below 70% or so there is no risk of explosion. Of course you still could have explosions in the heated flask and in other parts of the distillation setup, but the final handling, when all acid has come over is much safer in this case.

aquaregia - 11-5-2011 at 00:18

thx woelen.
on second toughts, the risk is not worth the chase...
I'll stick to KClO4 for now!
It's just that I like the way parts of my body are attached together just fine.

redox - 17-5-2011 at 16:28

What is KClO4's solubility in other polar solvents? Has anyone considered a displacement in non-aqueous media?

woelen - 17-5-2011 at 23:15

I tried dissolving in ethanol and methanol and acetone. In all of these it insoluble or only very sparingly soluble. I expect it to be even worse in other solvents, except maybe HF and liquid NH3. But in organic more or less polar solvents do not expect anything useful.