Ammonium sulfate

[Guest erik]

Currently we are producing Ammonium sulfate from a pipe reactor, but I would like to know when does Ammonium bisulfate form and how can I test for ABS in the AS? When does Ammonium pyrosulfate form? The reason I ask all these questions is that we produced hard rock slabs in the spray chamber and would like to know what we made and if we could convert that to AS powder?

 

thanks guys

[apathy]

I have no experience with your reaction scales, so I'm not exactly sure what it is you're doing, but who knows maybe I can help.

 

What is the reaction? Is it just ammonia + sulfuric acid?

 

If that is the case then ammonium bisulfate would form before ammonium sulfate as the reaction proceeds, which would just be a simple acid/base reaction. You could control this just by stoichiometry (adding half the ammonia (before driving off all the water of course, because while you've got water around all the weak acid/base equilibria come into play.))

 

Also, I would guess that the pyrosulfate stuff would form if you heated it to drive off water, but heated it too long or too high (but you'd really have to heat the piss out of it).

 

As for the rock hard stuff, is it water soluble? Is a little or a lot?

 

I actually have no idea if we are on the same page.

[Guest erik]

Thanks Apathy,

The reaction is taking place under pressure, adding water to dilute the H2SO4 to bring down heat of reaction when introducing ammonia gas in the reaction vessel. Usually a crystal forms but the water cut back to produce hard slabs instead of powder, but this rocks are water soluble. I thought the reaction would be:

2NH3(g) + H2SO4(l) → (NH4)2SO4

I think I get your drift with the weak acid/base equilibria, that's why ABS formation occurs before AS? Does the bisulphate convert to AS? Under which conditions?

[apathy]

Oh, if the slabs are water soluble then it just sounds like your just getting bigger crystals than you planned and it all caked together in the vessel. I don't see why your white rocks or slabs wouldn't be what you want (ammonium sulfate) or a mixture of that and ABS. And sure, ABS could surely get to AS with one more equivalent of ammonia (or even an excess of ammonia). Once the water and excess ammonia are driven off you should have solid AS (b/c sulfate has a -2 charge and no higher). If it's a powder or not just depends on how wet it is and how big the crystals are, based on my experience.

 

If I ever want to make the ammonium salt of an anion, I just react it's acid with excess ammonia, heat (if poss.) till I can't get any more ammonia out of it (on small scales just by holding pH paper over it and seeing if the vapors are still basic). Then I try to evap. the water somehow. Any leftover ammonia will leave before the last of the water. Ammonium stays behind with the anion leaving you with the salt. Should work for sulfate just fine.