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Author: Subject: Sulphuric acid from copper sulphate and sulphur dioxide???
Keras
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[*] posted on 12-8-2021 at 07:29
Sulphuric acid from copper sulphate and sulphur dioxide???


Folks,

For other reasons (geraniol synthesis from ß-pinene) I got interested in cuprous oxide. Surprisingly, the Handbook of Preparative Inorganic Chemistry states that cuprous chloride can be made thus:

2 CuSO₄ + 2 NaCl + SO₂ + 2 H₂O → 2 CuCl + Na₂SO₄ + 2 H₂SO₄

Which means sulphuric acid is a byproduct of the reaction.

Has anyone ever tried to make sulphuric acid this way? Just curious.

[Edited on 12-8-2021 by Keras]

Screenshot 2021-08-12 at 17.31.41.png - 152kB
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clearly_not_atara
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[*] posted on 12-8-2021 at 07:47


Note that if you're considering sulfuric acid yield (HoPIC wasn't), the end of the equation should really read:

... + 2 NaHSO4 + H2SO4
not
... + Na2SO4 + 2 H2SO4

I imagine it works, but the purification may not be easy and the economics are poor (1 mole of sulfuric acid for 2 moles of copper).




[Edited on 04-20-1969 by clearly_not_atara]
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[*] posted on 12-8-2021 at 08:47


Also Na2SO4 can crystallise with 2 and more moles of H2SO4. I remember Tsjerk mentioned some way to separate H2SO4 out of NaHSO4. By the way, I plan some experiments with SO2 oxidation in dissolved state using some interesting solvents.
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[*] posted on 12-8-2021 at 08:50


Quote: Originally posted by clearly_not_atara  
Note that if you're considering sulfuric acid yield (HoPIC wasn't), the end of the equation should really read:

... + 2 NaHSO4 + H2SO4
not
... + Na2SO4 + 2 H2SO4

I imagine it works, but the purification may not be easy and the economics are poor (1 mole of sulfuric acid for 2 moles of copper).


Oops, I didn't even check the equation. Thanks for that. Anyways, copper sulphate is so cheap it might be worth trying, especially for small batches of sulphuric acid.
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[*] posted on 12-8-2021 at 09:14


NurdRage has a video of making sufuric acid by reacting SO2 with CuCl2 solution. This is the same but without Na2SO4. CuCl2 could be recovered - it's work is only to be a catalyst.

[Edited on 12-8-2021 by teodor]
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[*] posted on 12-8-2021 at 14:16


Surely there isn't place on earth where this process is not cheaper and infinitely simpler by using 3% hydrogen peroxide (or a higher concentration) as the oxidant for SO2, right? Oxidation of sulfur dioxide by atmospheric oxygen is more or less what your reaction is accomplishing, facilitated by copper(II). If you're already producing the sulfur dioxide, I think it's far better to oxidize it without any metal salts present to complicate purification. It's very unlikely you'd ever get pure sulfuric acid from something not only containing not only dissolved copper, but also chloride ions.
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[*] posted on 12-8-2021 at 20:21


Teodor: I wouldn't call CuCl2 as catalyst in this reaction. If CuCl2 would be a catalyst, then it would be reformed in the reaction. But this isn't happening. You must convert CuCl in to CuCl2 in separate chemical process.



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[*] posted on 12-8-2021 at 22:04


@teodor: with methanol you can make sulfuric acid out of NaHSO4, surely you can use it to separate the two and make more sulfuric at the same time.

But isn't electrolysis of copper sulfate a traditional way of making sulfuric acid? I once did it in a practical course, I believe it involves one sacrificial copper electrode and it deposites copper on the other, or something like that. It can be done as a continuous process.
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[*] posted on 13-8-2021 at 00:04


@Bedlasky: yes, you are right. What I mean is that it is probably possible to find conditions when CuCl2 works as a catalyst for SO2 oxidation.

@Tsjerk: so, you can get sulfuric acid / methanol mixture but is it possible to separate them not loosing methanol?
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[*] posted on 13-8-2021 at 00:52


Quote:
Quote: Originally posted by Amos  
Surely there isn't place on earth where this process is not cheaper and infinitely simpler by using 3% hydrogen peroxide (or a higher concentration) as the oxidant for SO2, right? Oxidation of sulfur dioxide by atmospheric oxygen is more or less what your reaction is accomplishing, facilitated by copper(II).


Nah, there is no oxygen entering the reaction here. This is more a reduction of Cu²⁺ into Cu⁺ and a simultaneous oxidation of SO₂ into SO₃.

Quote: Originally posted by Amos  

It's very unlikely you'd ever get pure sulfuric acid from something not only containing not only dissolved copper, but also chloride ions.


Cuprous chloride is almost insoluble in water (0.047 g/L) and about all the CuCl will precipitate out, leaving a solution almost free from Cl⁻ anions and Cu⁺ cations.



[Edited on 13-8-2021 by Keras]
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[*] posted on 13-8-2021 at 00:57


Quote: Originally posted by Tsjerk  

But isn't electrolysis of copper sulfate a traditional way of making sulfuric acid? I once did it in a practical course, I believe it involves one sacrificial copper electrode and it deposites copper on the other, or something like that. It can be done as a continuous process.


I'm not sure you can produce sulphuric acid this way. If you reduce Cu²⁺ at the cathode, then what do you oxidise at the anode? Certainly not Cu – unless you want to look at a system doing nothing…
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[*] posted on 13-8-2021 at 01:35


Keras: Water is oxidized to oxygen.



If you are interested in aqueous inorganic chemistry look at https://colourchem.wordpress.com/main-page/

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[*] posted on 13-8-2021 at 02:01


You can still freely buy 15% sulfuric acid in EU. Something like 34 EUR per 20L. What could be interesting Keras, it if you can perform the reaction CuCl2 + SO2 (or any other way of SO2 oxidation) in 95% sulfuric acid, making oleum.
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[*] posted on 13-8-2021 at 02:27


SO2 + H2O2 is clean, good method.



If you are interested in aqueous inorganic chemistry look at https://colourchem.wordpress.com/main-page/

I can offer GC analysis of samples. Just U2U to me for more info.

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[*] posted on 13-8-2021 at 02:55


Quote: Originally posted by teodor  
if you can perform the reaction CuCl2 + SO2 (or any other way of SO2 oxidation) in 95% sulfuric acid, making oleum.


Well, it can be attempted.

The best way I know to make oleum is to pyrolyse sodium bisulphate at 800 °C. You need a quartz vessel, though, at these temperatures (Ref: Small-Scale Synthesis of Laboratory Reagents with Reaction Modeling)
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[*] posted on 13-8-2021 at 02:58


Quote: Originally posted by teodor  
You can still freely buy 15% sulfuric acid in EU. Something like 34 EUR per 20L. What could be interesting Keras, it if you can perform the reaction CuCl2 + SO2 (or any other way of SO2 oxidation) in 95% sulfuric acid, making oleum.


yep, i found 1 liter of 15% sulfuric acid as liquid ph lowerer for pools, but it's extremely expensive! 5 euros for 985 ml of water!

@Tsjerk: how to make sulfuric acid with sodium bisulfate and methanol?
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[*] posted on 13-8-2021 at 03:28


Quote: Originally posted by Keras  
Quote: Originally posted by teodor  
if you can perform the reaction CuCl2 + SO2 (or any other way of SO2 oxidation) in 95% sulfuric acid, making oleum.


Well, it can be attempted.

The best way I know to make oleum is to pyrolyse sodium bisulphate at 800 °C. You need a quartz vessel, though, at these temperatures (Ref: Small-Scale Synthesis of Laboratory Reagents with Reaction Modeling)


Probably you can try with 80-85% acid (this is easy to get boiling the acid of lower concentration) trying to saturate it with SO3 till 95-98% by SO2 oxidation (this concentration is much harder to get). This experiment avoids some unnecessary complications of handling oleum but should work as a proof of concept.

[Edited on 13-8-2021 by teodor]
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[*] posted on 13-8-2021 at 03:30


Quote: Originally posted by Bedlasky  
Keras: Water is oxidized to oxygen.


Not with a copper anode. You'd have to use a carbon anode for that.

[Edited on 13-8-2021 by Keras]
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[*] posted on 13-8-2021 at 05:47


Quote: Originally posted by Keras  
Nah, there is no oxygen entering the reaction here. This is more a reduction of Cu²⁺ into Cu⁺ and a simultaneous oxidation of SO₂ into SO₃.
Yeah, but maybe there should be if you want this to look like a practical method. CuCl is readily oxidized by air in the presence of chloride back to CuCl2. If you want to make sulfuric acid by this method, you would be better off using the copper chloride catalytically and bubbling air or oxygen through the reaction mixture along with the SO2.



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[*] posted on 13-8-2021 at 06:11


Quote: Originally posted by Texium  
Yeah, but maybe there should be if you want this to look like a practical method. CuCl is readily oxidized by air in the presence of chloride back to CuCl2. If you want to make sulfuric acid by this method, you would be better off using the copper chloride catalytically and bubbling air or oxygen through the reaction mixture along with the SO2.


Yeah, that'd probably work, except that re-oxidising CuCl into CuCl₂ might not be very efficient given CuCl is so insoluble. I think more than a catalytic amount is needed, and good stirring must be maintained to insure intimate contact between air and the powder.

I wonder if the most economical method is not just bubbling SO₂ into water forming sulphurous acid and let it oxidise spontaneously to sulphuric acid.
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[*] posted on 13-8-2021 at 06:26


Why don’t you try something and stop wondering?



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[*] posted on 13-8-2021 at 07:13


Quote: Originally posted by Texium  
Why don’t you try something and stop wondering?


Lol, because I’m away on holiday and nowhere near my lab right now!

[Edited on 13-8-2021 by Keras]
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[*] posted on 13-8-2021 at 22:24


Spontaneous oxidation of SO2 solution? This won't happen.



If you are interested in aqueous inorganic chemistry look at https://colourchem.wordpress.com/main-page/

I can offer GC analysis of samples. Just U2U to me for more info.

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[*] posted on 14-8-2021 at 10:45


Quote:
Quote: Originally posted by Amos  
Surely there isn't place on earth where this process is not cheaper and infinitely simpler by using 3% hydrogen peroxide (or a higher concentration) as the oxidant for SO2, right? Oxidation of sulfur dioxide by atmospheric oxygen is more or less what your reaction is accomplishing, facilitated by copper(II).


Nah, there is no oxygen entering the reaction here. This is more a reduction of Cu²⁺ into Cu⁺ and a simultaneous oxidation of SO₂ into SO₃.

Quote: Originally posted by Amos  

It's very unlikely you'd ever get pure sulfuric acid from something not only containing not only dissolved copper, but also chloride ions.


Cuprous chloride is almost insoluble in water (0.047 g/L) and about all the CuCl will precipitate out, leaving a solution almost free from Cl⁻ anions and Cu⁺ cations.



[Edited on 13-8-2021 by Keras]


Of course, I've forgotten about the wealth of available oxygen atoms present in the compound CuCl2! You might be right in that oxygen isn't directly involved in the more interesting of the chemical reactions going on here. Sulfur dioxide may well just be oxidized to chlorine-containing intermediates and immediately hydrolyzed. But hydrogen chloride is a byproduct, and cuprous chloride is soluble in solutions of HCl and rapidly oxidized back to CuCl2 by atmospheric oxygen. Given any amount of time, oxygen would begin to contribute very substantially to the process, which is why even before my comment, we were already talking about CuCl2's ability to perform as a catalyst only. I don't think you would be able to appreciably exclude these addtional reactions from happening. Any product you produce via this reaction will inevitably contain hydrogen chloride and non-negligible concentrations of copper ions, which would wreak havoc on many of its uses.

[Edited on 8-14-2021 by Amos]
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[*] posted on 23-8-2021 at 03:20


Quote: Originally posted by teodor  
You can still freely buy 15% sulfuric acid in EU. Something like 34 EUR per 20L. What could be interesting Keras, it if you can perform the reaction CuCl2 + SO2 (or any other way of SO2 oxidation) in 95% sulfuric acid, making oleum.


What possible use would a person or business use 15%h2so4 for?
It seems too diluted for drain cleaning
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