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Author: Subject: SO3 a different way
497
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SO3 a different way

So i had an idea today: take a very corrosion resistant canister, maybe glass, fill it completely with NO2 gas, then pressurize it up to maybe 3-5 bar with 2:1 SO2-02 mix. The NO2 should facilitate the SO2 + O --> SO3 reaction, probably quickly under the higher pressure.

Once the SO3 partial pressure is sufficiently high it should condense and accumulate at the bottom, and continue adding the the SO2-O2 mix to keep the pressure up. None of the other gases would condense unless you raised the pressure too far or cooled it too much. SO3 + NO2 in liquid form... tasty...

Once you're satisfied with the amount of SO3, you should be able to cool the canister and release the pressure, pour off the SO3 and make whatever variety of oleum/sulfuric acid you want.

I imagine a semi-continuous process but it could be done in batches if need be. I would love a glass setup but it would be a little scary having such nasty things under that much pressure in glass. I was thinking a stainless steel cylinder, maybe plated with something a little more resistant... maybe teflon coated?

Things I like about this: no high temps, no catalysts, fairly simple apparatus, can make any concentration of acid and even better oleum. The biggest downside is the pressurized toxic gases... but hey, I think I'd rather have that than 400 degree SO3...

The biggest problem I see is getting the SO2 and O2 in at the right ratio, if they were just a little off one would accumulate and things would stop working. This might be solved by running a batch process. I was thinking of liquefying the SO2 produced from burning sulfur. You could just buy a canister too. O2 is easy to get from any welding shop.

So my question is: would this work? And could it possibly be easier than the various other methods seen on this forum?

[Edited on 4-2-2008 by 497]
garage chemist
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That's going to make nitrosylsulfuric acid, and nothing else.
SO3 and even H2SO4 react very readily and immediately with any NO/NO2, forming the said compound.

Thats why the lead chamber process can only produce dilute H2SO4, because the nitrosylsulfuric acid has to be hydrolyzed with water to get the catalyst nitric oxide back.
And the nitric oxide in the exit gas is washed out with conc. H2SO4 for returning it into the process.

The NOx-catalysed SO2 oxidation is a very complex reaction with many intermediate compounds. It is impossible to get the lead chamber process to produce SO3, or even conc. H2SO4.

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497
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Hmm I was afraid of that... but there is no hydrogen (water) being introduced hopefully, so are you saying you would get an SO3 condensate with NO2 dissolved in it (or some other exotic nitrogen sulfur oxygen compound) that would make nitrosylsulfuric acid as soon as it was added to water?
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I believe that the actual oxidation is of "H2SO3" by HNO2 and related ions. So some water is needed to make the reaction run, and the SO3 formed is competing for that water. Once the concentration of water drops low enough, chamber crystals - nitrosylsulfuric acid - will form.

Be easy to try it at a test tube or small flask scale, if you wanted to experimentally confirm Or the answer may be buried in the chamber process thread.

You may also be interested in the page here (paste into browser bar)

a 1992 book which says it appears NOx + H2O => NO2(1-) {not balanced} then SO2 is oxidised by that through some messy steps.

[Edited on 5-2-2008 by not_important]
497
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Would it be possible to just make nitrosylsulfuric acid and then purify it?

"Decomposes in water to form sulfuric and nitric acids [Merck 11th ed. 1989]. Nitrosylsulfuric acid reacts vigorously with water to generate gaseous NO2. In experiments at Argonne National Laboratory, in which it was mixed with water and stirred at room conditions, about 94 percent of the theoretical yield of NO2 evolved as a gas in the first 3 minutes"

I suppose if you did this you would end up with fairly dilute sulfuric acid though.

[Edited on 5-2-2008 by 497]
497
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What if you simply charged the vessel with 1:1 ratio of NO2 to SO2 at like 8 bar and let it react (if it actually would without water and such)? wouldn't you end up with a bunch of NO gas and SO3 condensate or at least some SO3? easy enough to try, doing it that way sounds even easier actually, then you could reoxidise the NO when you were done and do it again.
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The problem with this type of reaction is that water is needed. Dry SO2 hardly works as a reductor. I actually tried what you suggest. Dry NO2 does not react with dry SO2. I put a mix of both gases in a bottle and if that is done, nothing changes. If a drop of water is added to this bottle, then soon, a white solid is formed, which settles on the glass walls. This white solid is the nitrosylsulfuric acid, mentioned above.

I did a similar experiment by pouring 1 ml of thionylchloride in dry NO2 gas. When this is done, part of the NO2 gas dissolves in the thionylchloride, but nothing else happens. Again, when a drop of water is added, then a white solid is formed, and the bottle gets pressurized (due to formation of HCl).

Dry SO2 is remarkably reluctant to oxidation. Even iodine does not act upon it. I2 in dry SO2 does not react at all. Heating the bottle gives a nice purple gas mix, nothing else. As soon as a drop of water is added to such a mix, everything becomes brown and a fume of HI is formed.

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497
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that is unfortunate... I've read that solid nitrolsylsulfuric acid decomposes at around 70C but I imagine it would just yield SO2+NO2+H2O, nothing useful... well I'm a little less energetic in my search for easy H2SO4 now that I just bought 19 liters of battery acid for $15 today. garage chemist chemical wizard Posts: 1803 Registered: 16-8-2004 Location: Germany Member Is Offline Mood: No Mood I thought SO3 was the goal, not just H2SO4? The chamber process works really quite well in an amateurs hands as axehandle has shown. You could develop it further- we'd all like to see some interesting new contribution to the chamber process thread. For SO3, you'd be better off making ferric sulfate from some of your H2SO4 and doing the ancient vitriol process that gives fuming H2SO4. That's what I'm working on at the moment. www.versuchschemie.de Das aktivste deutsche Chemieforum! 497 International Hazard Posts: 778 Registered: 6-10-2007 Member Is Offline Mood: HSbF6 Well I was originally looking for SO3 but the only use i have for it at the moment would be to make concentrated H2SO4 for nitrating things, etc. The whole idea was more of a theoretical thing anyway, I don't know if I would have the time to mess around with it any time soon. The lead chamber process is lovely, I agree, and I'd love to improve on it... but as I said, free time is minimal. On that note, my understanding of the lead chamber reaction is (probably oversimplified greatly): NO2 and SO2 dissolved in water make nitrosylsulfuric acid which decomposes into NO and H2SO4 and then the NO being not very soluble is reoxidized by O2 gas. Once the H2SO4 content is high enough there is not enough free water to decompose the nitrosylsulfuric acid and the reaction stops. Am I totally off here or what? I'll have to read over the Lead Chamber thread again, its been a while... Thanks for taking the time to think about/correct my ramblings. Pixicious Harmless Posts: 31 Registered: 28-1-2008 Member Is Offline Mood: Smiley No you are not. I have heard of the same reaction. http://www.fullbooks.com/An-Introduction-to-Chemical-Science... It is mentioned here. I'm more interested in 497's freezing process. I'm sure it doesn't work but I am so interested to knowing why if it does. Baphomet Hazard to Others Posts: 211 Registered: 19-11-2006 Member Is Offline Mood: No Mood  Quote: well I'm a little less energetic in my search for easy H2SO4 now that I just bought 19 liters of battery acid for$15 today

Lucky bastard! In my city drain cleaner costs \$50 for a 2 litre bottle

Anyway.. SO3 is easy. Decompose CuSO4 with heat, and bubble the gas straight into water if you want H2SO4.

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497
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My drain cleaner is a similar price too. Which is unfortunate because it is annoying to have to boil down battery acid all the time. And then it still doesn't end up as concentrated as it really should be many things.

As far as SO3 goes, I still like the idea of HPO3 + H2SO4 --> SO3 + H3PO4... have to try that some time.

If you really want to decompose sulfates, I think FeSO4 is the way to go. Unless you have some excess fuel you need to burn off heating CuSO4...

[Edited on 25-9-2008 by 497]
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Yeah.. let me try FeSO4 and get back to you. Presumably it is cheap? They practically give bluestone away

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497
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Yes I believe its pretty cheap, although I've never actually bought it. If it wasn't you could always get some dirty old H2SO4 from dead car batteries and react that with some scrap iron.