teodor
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Oxidation of SO2 to SO3 in pyrosulfuryl chloride
Pyrosulfuryl chloride can dissolve SO2 in the amount of 40 to 50% by weight. It is also highly miscible with SO3 forming different solutions which
probably could be used handier than SO3 itself.
The only open question is how to oxidize SO2 to SO3 in this medium.
Any ideas? Catalysts?
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Bedlasky
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Persulfate????
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teodor
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I am afraid it will create some very strong ionic bond with some of polysulfuric acid anion (with more than 2 S atoms) and you know this story of
getting SO3 out of pyrosulfate...
I am afraid that even barium salt will be highly soluble in such a medium.
But some metal which doesn't form a stable compound with those anyons - probably, if it exists.
Of course, I assume here the existence of polysulfuric acid anions with more than 2 sulfur atoms. If they do not exist, OK, we can get some free SO3,
but still with metal ions contamination.
But surely we can try to do it and follow with a distillation. It could work but will not meet my initial goal of doing everything in a liquid phase.
[Edited on 1-10-2021 by teodor]
But it is still could be useful for preparation some complex like SO3 * pyridine.
[Edited on 1-10-2021 by teodor]
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clearly_not_atara
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Where are you planning to get pyrosulfuryl chloride, is my first question...?
Anyway, since we are already looking at the far end of nastiness, I think the natural candidate oxidant is ozone -- any NO2 "contaminant" will likely
prove helpful as well!
[Edited on 04-20-1969 by clearly_not_atara]
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teodor
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I plan to get pyrosulfuryl chloride by dehydrating chlorosulfonic acid with phosphorus pentoxide and purification of the result by neutralizing acids
& distillation or extraction with suitable solvent. There are also other possible routes but I plan to start experiments with P2O5.
Yes, O3 was my initial thought. Also, I am a bit worried about losing SO3 with a gas stream but with O3 I think the losses will be less than O2 +
platinum or whatever -theoretically because practically it will be still mainly O2.
The next candidate is probably NO2 but it requires some digging into the chemistry of S-N bonds to see how it should be purified.
Maybe chlorine can do the job, but we will get not SO3 but probably chlorosulfonic acid. That is also interesting, of course, but is not our defined
goal.
CrO3 will probably contaminate the result but still, it would be interesting if it can work here.
[Edited on 1-10-2021 by teodor]
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clearly_not_atara
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The reaction of SO2 with Cl2 produces sulfuryl chloride, which is basically just a liquid chlorinating agent with few other useful properties (but you
can make sulfamide!).
NO2 rxn with SO2 will not produce S-N bonds; sulfur-nitrogen compounds are all thermodynamically unstable and their formation must be driven by the
formation of some low-energy compound like HCl. The only byproducts of significance would be nitrosonium or nitronium chlorosulfonate, or NOCl, but
I'm not sure if that will be generated either. But NO2 is also a gas, not much less toxic than O3, and generating a dry stream is not necessarily
easy.
[Edited on 04-20-1969 by clearly_not_atara]
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teodor
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I see your point, this gas is of hygroscopic nature. Probably 2 pipes - one with dry NO and one with dry O2 could work better. But moisture just will
add some H2SO4 which generally could not be avoided completely because SO3 is not less hygroscopic.
I am more concerned about losing SO3 during this process than getting some H2SO4 impurity, which could be ok at the beginning. But for checking how
much we can lose I suspect NO2 is the best candidate to try if we are talking about gases.
As for the dangers of this gas you also have a valid point but considering other alternatives of SO3 preparations and the danger of the resulting
compound itself it is something we probably can live with.
But still, I will be glad to find some magic salt or oxide which I can just mix and filter out of the SO3 solution and not generate/purify gases.
[Edited on 1-10-2021 by teodor]
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clearly_not_atara
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On further consideration, you might consider chlorine dioxide, which is a liquid below 11 C.
[Edited on 2-10-2021 by clearly_not_atara]
[Edited on 04-20-1969 by clearly_not_atara]
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wg48temp9
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I was curious about the synthesis Pyrosulphuryl Chloride I found a paper on Pyrosulphuryl Chloride and Chlorsulphonic Acid. I have attached copy.
Attachment: Pyrosulphuryl-Chloride-20022774.pdf (4.7MB)
This file has been downloaded 222 times
I am wg48 but not on my usual pc hence the temp handle.
Thank goodness for Fleming and the fungi.
Old codger' lives matters, wear a mask and help save them.
Be aware of demagoguery, keep your frontal lobes fully engaged.
I don't know who invented mRNA vaccines but they should get a fancy medal and I hope they made a shed load of money from it.
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teodor
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The method of reaction between CCl4 and SO3 for pyrosulfuryl chloride is unacceptable because of COCl2.
Brasted in "Comprehensive inorganic chemistry" mentions dehydration of HClSO3 with P2O5. There is neither procedure nor reference given. Some other
authors point to this book as a reference. The formation of (poly)phosphoric acids is problematic for reflux and distillation but I have to try.
Another method is the reaction
2 PCl3 + 8 HClSO3 = P2O5 + 3 S2O5Cl2 + 8 HCl + 2 SO2
which doesn't form phosphoric acids so is more friendly for glassware (reflux/distillation) but uses less available reagent.
But I didn't find the procedures so those are subjects for experiments. I hope I will share some results.
Oxidation of SO2 with NO2 doesn't happen without water according to Brasted. Probably there are some other catalysts.
Also, oxidation of SO2 to SO3 gives 29kcal, so temperature control is required.
Chlorine dioxide will introduce chlorine which can form stable compounds with SO2/SO3 (sulfuryl chloride, pyrosulfuryl chloride?)
Bromine can probably work better because the corresponding compounds are less stable but still some of them probably exist.
[Edit]
Now I start to realize that the reduction abilities of SO2 in the case of a water-free solution are completely different. I remember Woelen posted a
link to his experiment of mixing SOCl2 with H2SO4 and K2Cr2O7 and the mix was unable to oxidize sulfur in thionyl chloride without water.
I think the conditions of oxidation SO2 to SO3 in an anhydrous environment should be similar to oxidation of SOCl2 to SO2Cl2. I didn't study this
topic much (yet) but according to Wikipedia there are 2 reactions:
SOCl2 + HgO → ClSSCl + HgCl2 + SO2Cl2
2 SOCl2 + MnO2 → SO2 + MnCl2 + SO2Cl2
By the way, in a water solution, SO2 reacts with MnO2 forming the dithionate anion. So, it is not quite clear what could happen in anhydrous
conditions with MnO2. Another interesting option would be KMnO4 which probably can form Mn2O7 in situ in this solution.
[Edited on 2-10-2021 by teodor]
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teodor
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Update.
Strictly speaking, there is no such thing as "solution of SO3 in S2O5Cl2". There is a series of compounds SnO3n-1Cl2. By
oxidizing the saturated solution of SO2 we probably get the first one, S3O8Cl2. From Robert Brasted, "Comprehensive inorganic chemistry, Volume VIII",
p. 105:
"
The S3O8Cl2 is a colorless mobile liquid, soluble in CCl4 and benzene, but insoluble in concentrated sulfuric acid. The melting point is 18.7C with
decomposition to pyrosulfuryl chloride, S2O5Cl2, and SO3 at 116C. ... The hydrolysis in ice water is slow.
"
So, the remarkable property of this SO3 "solution" is that it is not hydrophobic (even could be separated by concentrated H2SO4).
Probably I will try to isolate and study this compound.
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woelen
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Are these compounds really stable? SO2Cl2 also is not fully stable. I have a small quantity of this, and it is a pale green liquid, which consists of
SO2Cl2, with SO2 and Cl2 dissolved in it. The green color is due to the formation of the Cl2.
I can imagine that S2O5Cl2 and S3O8Cl2 also partially decompose to SO2 and Cl2 and the SO3 then can go into formation of even higher compounds, e.g.
S2O5Cl2 <---> SO2 + Cl2 + SO3
S2O5Cl2 + SO3 <---> S3O8Cl2
So, "pure" S2O5Cl2 might actually be indeed mostly S2O5Cl2, but also some free SO2 and Cl2 and some S3O8Cl2. It would be interestng to see actual
pyrosulfuryl chloride. Does this remain colorless, or does it turn green over time. SO2Cl2 turns green quickly. Fortunately it does not become
pressurized in a closed vessel, the SO2 and Cl2 remain dissolved in the liquid and the equilibrium is mostly at the side of SO2Cl2. It is even safe to
ampoule SO2Cl2 (I did several years ago, and I still have the nice display sample).
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teodor
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I don't know but I hope I will check it. There is a sharp melting point for S3O8Cl2 at least in one book.
I have mixed stoichiometric amounts of P2O5 (P4O10) and HClSO3. P2O5 was immediately dissolved without heat evolution. After some time a few big
crystals formed on the bottom of the flask. I keep the flask in a freezer at -18C but it is still liquid.
Now I am thinking about neutralizing all the acid and looking at what will remain after that.
I try to find a compound that will neutralize both phosphoric and chlorosulfonic acid. I am thinking about CaCl2. Do you have any other ideas?
[Update]
I found the original article which mentioned the method of preparation with P2O5. Unfortunately, I don't read French, Could somebody who knows French
at least point me to where is the procedure described, I will try to translate by myself:
https://www.biodiversitylibrary.org/item/28062#page/652/mode...
[Edited on 4-10-2021 by teodor]
[Edited on 4-10-2021 by teodor]
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