vulture - 26-11-2002 at 09:20
Since P2O5 (actually P4O10) is so hard to get, I was wondering about using SO3 as a dehydrating agent.
First problem: Is it strong enough to chemically break away H2O from organic molecules?
Second: Preparation of SO3. Instead of the usual contact process, I was thinking about a stoichometric mix of a strong oxidizer (excess) and sulfur
which is then burned in the presence of V2O5 (which I can get without much problems).
Maybe filling the reaction chamber with oxygen prior to starting the reaction if necessary.
Any thoughts?
BASF - 26-11-2002 at 09:55
-What about leading SO2 over a platinum catalyst at 500°C in the presence of an excess of air?
The needed catalyst can be made quite easily: aqua regia on lets say 20mg platinum wire>hexachloroplatinum acid
hexachloroplatinum acid + NH3>ammoniumhexachloroplatinate(insoluble)
This is then heated under red glow to yield finely devided platinum.
As carrier i propose using kieselguhr, which resists the high temp and has a very big surface.
-But maybe the thermal decomposition of Na2S2O7 at 460°C would be easier.
Na2S2O7 forms when NaHSO4 is thermally decomposed.
But you can also decompose CuSO4, FeSO4.
In 16-18th century sulfuric acid was mainly produced by thermal decomposition of sulfates("vitriols").
(Nordhäuser-process)
HLR
madscientist - 26-11-2002 at 10:00
I believe that sulfamic acid decomposes to sulfur trioxide and ammonia at somewhere around 200C.
HSO3NH2 --(heat)--> SO3 + NH3
rikkitikkitavi - 26-11-2002 at 11:05
I seriously doubt that decomposing sulfamic acid into SO3 and NH3 would yeild any significant amounts of SO3, since SO3 reacts vigourously even with
water (i e steam explosion)
SO3 can more easily be made by decomposing sodium bisulfate
2NaHSO4=> Na2S2O7 + H2O @ 300-400 C
Na2S2O7 => Na2SO4 + SO3 @ 600-700 C.
SO3(g) reacts with water vapour forming sulfuric acid mist with extremely fine droplets.
Even if SO3 isnt strong enough, just a faint addition of H2O forms conc H2SO4 (actually oleum ) and H2SO4 + organic materials, well you know what can
happend...
If P4O10 is so hard to get, why not make it ? Almost all P in the world is made by heating CaPO4 + SiO2 + C =>
CaSiO2 + CO+ P @ 1300 C.
The high temperature is needed for the reduction to free P. However , by emitting the C and just heating (melting) CaPO4 and SiO2 in the right
proportions should yield PxOy which distills of (volatile) and shifts the reaction towards CaSiO2 and PxOy. The latter is immediately reacted in air
to P4O10.
It sounds like a feasible dry distillation, however might take some serious temperatures involved (~1000 C) .
I have to admitt I havent tried it, but the idea has come into my mind a few times.
If course the P4O10 is condensed into kerosene or some similar hydrocarbon free of oxygen.
/rickard
rikkitikkitavi - 26-11-2002 at 11:08
BTW
I belive some search for patents of how to make P and P4O10 would come up with some answers, since P is made on the multi million tonne scale per
annum.
/rickard