Sciencemadness Discussion Board

Synthesis of Sulfur trioxide method proposal

largenumbergoeshere - 20-8-2018 at 22:10

I live in NSW, Australia and sulfuric acid is difficult to track down and is never sold at a decent price.

I have designed a setup for the production of sulfur trioxide for sulfuric acid production on the laboratory scale but I am concerned with specific safety and otherwise details I could not find online.
It is based on the industry standard contact process.
An amount of sulfur is placed in a three joint round bottom flask and ignited and air is then pumped through with a 12Volt pump, and fed into an air condenser with a bed of vanadium pent-oxide, heated with a Bunsen burner. The produced sulfur trioxide is condensed into another flask and any remaining sulfur dioxide and impurities are bubbled through an aqueous sodium hydroxide solution to produce sodium sulfite which can then be used to recover the sulfur dioxide.
The sulfur trioxide will be added to concentrated sulfuric acid and then added carefully to water to produce sulfuric acid.

My main safety concerns are supposed arsenic impurities in the sulfur, if any nitrogen will react with the burning sulfur and if the sulfur will burn to hot for the flask.
My other thoughts are will the powdered catalyst be sufficient to react most of the sulfur dioxide and will the sulfur sustain a flame.

I have provided a very crude diagram to highlight the proposed glassware layout. Unfortunately I don't have the time to correct it.

Any thoughts, recommendations and concerns are welcome. Thank-you for reading

Monstrocity.jpg - 91kB

mackolol - 20-8-2018 at 22:48

This is much more OTC and easier method for making sulphuric acid.
https://www.youtube.com/watch?v=l2AkVYxDSKc&t=207s

largenumbergoeshere - 20-8-2018 at 23:06

I'll certianly give it a go but it seems a bit less practical for producing large quantities. Thankyou for the suggestion.

Hendrik - 21-8-2018 at 00:33

This method should work theoretically, but SO3 is no joke. A much safer method for the synthesis of H2SO4 uses SO2 and H2O2. The concentration and the quantities obtained may be low, but at least you won't have to deal with highly dangerous SO3.

j_sum1 - 21-8-2018 at 00:52

U2u sent. There is a good source of sulfuric acid in Oz.

Other avenues that might be suitable: SO3 from decomposition of sodium bisulfate at high temperature. Electrolysis of copper sulfate. (I have lots of experience of the latter and can give a procedure if you wish.)

J.

Chemetix - 21-8-2018 at 01:49

Thermal decomposition of Aluminium sulphate at 700C seems a fairly workable route to SO3, the decomposition is proportional to temperature and is easily controllable. But SO3 is nasty stuff that deserves respect and a healthy amount of fear. I agree with Jsum, if you can find another way do it. If not, then safety all the way with this project.

My experience with trying to burn sulphur to make SO2 was fraught with difficulty, the sulphur melts and forms a high molecular weight polymer which caps the burning sulphur and prevents it from burning. The Lurgi sulphuric plants have a high speed rotating drum to force the molten sulphur through the orifices of the barrel to burn away from the polymers to get around this problem. The other problem is sulphur vapour.

Sulphur is normally S8 but can become a smaller number or individual atoms, that are quite volatile. My sulphur burning plant had sulphur condensing everywhere and clogging just about everything. Industry must use high pressures to force the sulphur to condense so as to prevent it clogging the catalyst beds and everything else.

largenumbergoeshere - 21-8-2018 at 02:08

Quote: Originally posted by Chemetix  
Thermal decomposition of Aluminium sulphate at 700C seems a fairly workable route to SO3, the decomposition is proportional to temperature and is easily controllable. But SO3 is nasty stuff that deserves respect and a healthy amount of fear. I agree with Jsum, if you can find another way do it. If not, then safety all the way with this project.

My experience with trying to burn sulphur to make SO2 was fraught with difficulty, the sulphur melts and forms a high molecular weight polymer which caps the burning sulphur and prevents it from burning. The Lurgi sulphuric plants have a high speed rotating drum to force the molten sulphur through the orifices of the barrel to burn away from the polymers to get around this problem. The other problem is sulphur vapour.

Sulphur is normally S8 but can become a smaller number or individual atoms, that are quite volatile. My sulphur burning plant had sulphur condensing everywhere and clogging just about everything. Industry must use high pressures to force the sulphur to condense so as to prevent it clogging the catalyst beds and everything else.


So would you say it's simply not worth the trouble on this scale then?

Chemetix - 21-8-2018 at 02:19


"So would you say it's simply not worth the trouble on this scale then?"

How much acid do you want to produce? A small apparatus as you have described will produce very small amounts of poor quality acid, but that may all you want or need. If you need a litre or two of 98% high purity, then this scale is not likely to be of any use.

I remember being able to get 500gm SO2 canisters from winery supplies once upon a time. Better than trying to burn sulphur to feed a catalytic oxidiser.

largenumbergoeshere - 21-8-2018 at 02:24

Thankyou for your suggestions.
I understand the dangers of SO3 and you are right to imply I am not taking it very seriously. I don't yet have much experience but most of the chemistry I find interesting requires a decent amount of sulfuric acid as a reagent or in most cases a catylist.

Maybe down the road i might consider making it via salt decomposition or electrolysis for thier own sake but for now my best choice by far seems to buy it from cyndan for $20/L as j_sum1 suggested.

Keras - 21-8-2018 at 02:29

How come sulfuric acid is so hard to source down under? Over here, you can even grasp a bottle of it (I mean, around 40% concentration) at any convenience store. And I mean, the bottle is plainly labeled "sulfuric acid", it’s not even sold as a drain cleaner or plug remover.

j_sum1 - 21-8-2018 at 02:46

Well, we can buy hydrochloric acid like that...

It always stikes me as odd when people resort to pvc pyrolysis or other crazy activities to get HCl.

largenumbergoeshere - 21-8-2018 at 03:01

Quote: Originally posted by Keras  
How come sulfuric acid is so hard to source down under? Over here, you can even grasp a bottle of it (I mean, around 40% concentration) at any convenience store. And I mean, the bottle is plainly labeled "sulfuric acid", it’s not even sold as a drain cleaner or plug remover.

To be honest I don't know. I guess most of sulfuric acid's cleaning opperations can be replaced with a base that sounds a lot less scary than an acid. I don't know about other countries but With "chemicals" people seem to be very conservative over here. Natural, organic and pestecide free things are all the rage.
EDIT: Along the same lines fireworks are illegal to buy in all but a 2 states, only one with legislation being completely relaxed.

[Edited on 21-8-2018 by largenumbergoeshere]

[Edited on 21-8-2018 by largenumbergoeshere]

largenumbergoeshere - 21-8-2018 at 03:06

Quote: Originally posted by j_sum1  
Well, we can buy hydrochloric acid like that...

It always stikes me as odd when people resort to pvc pyrolysis or other crazy activities to get HCl.

What? That sounds increadibly dangerous. Doesn't PVC tend to form dioxins and other unexpected toxic nonsense when burnt?

j_sum1 - 21-8-2018 at 03:26

Pyrolysis is not burning.
There is a procedure. I have never tried it.

Melgar - 21-8-2018 at 19:41

I had some limited success with the contact process, but H2SO4 is really easy to get in the US, so I wasn't ever that invested in making it practical. I can give you some tips though. First off, for small-scale setups, it works a lot better to suck the SO2 into your air stream with something like a Venturi tube. Reason being, it's hard to keep your air flow at a rate that's high enough to keep the fire burning and low enough that the air doesn't blow the fire out. And the low-flow-rate air pumps tend to pulse the air stream which just about always blows out your fire. Sulfur fires are pretty easy to accidentally blow out.

It also works a lot better if you're able to raise the oxygen concentration of the air, whether with an oxygen tank from a welding torch or one of those pressure-swing adsorption devices.

Also, you can generate considerable amounts of SO2 by burning DMSO. DMSO burns a lot more readily than molten sulfur, and at least for me, it's common to have impure DMSO laying around from some extraction or whatever. I never used SO2 obtained this way for the contact process, since it consumes a lot more oxygen per unit of SO2 that forms. It still might be worth knowing though.

If you burn methylene chloride or chloroform or tetrachloroethylene or even PVC in a hot enough fire with plenty of oxygen, you can theoretically condense the vapors to get hydrochloric acid. This is how trash incinerators avoid that problem, and also why trash incinerators have to be so well-maintained. But these substances strongly inhibit combustion, so you have to mix them with some other substance that's more flammable. I've only done this with methylene chloride; I'd gotten some phosgene indicator strips and wanted to test them. So I mixed a tiny amount of nitromethane, methanol, and methylene chloride together and burned it with strong ventilation, but no phosgene was produced at all. The chlorine atoms all just formed HCl in the combustion gases. I guess I'm not surprised, but I did feel a little silly about how careful I'd been to keep methylene chloride away from open flames for fear it might form phosgene.

Keras - 23-8-2018 at 00:42

Quote: Originally posted by largenumbergoeshere  

To be honest I don't know. I guess most of sulfuric acid's cleaning opperations can be replaced with a base that sounds a lot less scary than an acid. I don't know about other countries but with "chemicals" people seem to be very conservative over here. Natural, organic and pestecide free things are all the rage.
EDIT: Along the same lines fireworks are illegal to buy in all but a 2 states, only one with legislation being completely relaxed.


That’s strange. There are a lot of things you can’t do with sodium hydroxide, even at high concentrations. You don’t use lead batteries in cars anymore in Oz?

[Edited on 23-8-2018 by Keras]

j_sum1 - 23-8-2018 at 00:45

Yes. Standard lead acid batteries are used. You just cannot buy the acid otc without also buying the battery. Not the cheapest way of getting sulfuric acid.

Alkoholvergiftung - 23-8-2018 at 01:01

You can make SO3 when you heat NaHSO4 water free and MgSO4 Water free. It makes an double salt MgNa2(SO4)2 and SO3. Thats they way the recycelt the hydrogensulfate bevore ww1.

Other Methode wenn you heat gyps or MgSO4 2 parts and 1 part ironoxyde but you Need 700 or 800 C for this reaction.

Keras - 23-8-2018 at 01:24

Quote: Originally posted by j_sum1  
Yes. Standard lead acid batteries are used. You just cannot buy the acid otc without also buying the battery. Not the cheapest way of getting sulfuric acid.


So bogan! :P

mackolol - 23-8-2018 at 03:59

You can also decompose thermally FeSO4 to Fe2O3 SO2 and SO3. It's cheap as dirt and temperature of flame should be enough.

barbs09 - 23-8-2018 at 04:00

Melgar's post describing the sucking of sulphur dioxide through the catalyst reminded me of an old article possibly from Popular Science (1930's vintage??) describing a small-scale Contact type preparation using a heated iron oxide catalyst and drawing the gasses via the siphoning action of water.

I wonder if the iron oxide was replaced by V2O5, the efficiency would be markedly improved?

j_Sum1, I would be interested in seeing your procedure for producing H2SO4 via the Electrolysis of copper sulphate please.

Cheers



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clearly_not_atara - 23-8-2018 at 09:03

Still another possibility is the disproportionation of potassium or possibly ammonium bisulfate in the presence of ethanol:

https://www.sciencemadness.org/whisper/viewthread.php?tid=79...

Ammonium bisulfate is generally very easy to obtain because ammonium sulfate is a common fertilizer which can be pyrolysed to obtain the bisulfate (and NH3 gas).

Alkoholvergiftung - 23-8-2018 at 12:31

Mackolol. You mean the middleage Vitriol Burning. but its better to dry it in an pan so you get Fe2(SO4) and than destill it at 400C you get so an much higher yield.