Sciencemadness Discussion Board

Make SO3 by oxidizing SO2 with KClO3?

metalresearcher - 17-12-2013 at 12:49

Well, I thought about a setup with burning sulfur and leading the resulting SO2 over (molten) KClO3 and making use of its strong oxidizing properties especially at elevated temperatures. My hope is obtaining SO3 which can be combined with water
to H2SO4.
Does this work ?

Bot0nist - 17-12-2013 at 13:01

I had luck just melting S and mixing in enough potassium nitrate to keep it burning good. The reulting "pucks" burned slowly and controlled in a semi sealed vessle, and the fumes absorbed into water to give dilute sulfuric acid... Surface contact of the gas to the moltent salt may be a issue.

Marvin - 18-12-2013 at 04:00

metalresearcher, I can think of at least 4 reasons that is a bad plan. Think about the chemistry and see how many you can guess. You need to review basic safety information regarding chlorates.

plante1999 - 18-12-2013 at 05:04

Buy some platinized asbestos...

Zyklon-A - 18-12-2013 at 09:05

Try the lead chamber process, it worked well for me.
KNO3 is much cheaper than KClO3 and it is known to work, unlike your plan, also the setup for the lead chamber process is much more simple.

Random - 18-12-2013 at 09:14

Isn't this going to be armstrongs mixture if something goes wrong?

plante1999 - 18-12-2013 at 09:35

Metal researcher, I have a procedure for the lead chamber process in my lab scale industrial process, available in the pre-pub sub forum. Or you could try the contact process, worked really well for me.

AJKOER - 18-12-2013 at 09:57

OK, for those interested in a simple inexpensive route to SO3, may I suggest the thermal decomposition of Aluminum sulfate. Source, see . Cited reaction occurring at 770 C per Wikipedia:

Al2(SO4)3 (s) =Heat=) Al2O3 (s) + 3 SO3 (g)

I am investigating some simple paths for the home chemists to prepare Aluminum sulfate. For example, dissolving Al in aqueous NaHSO4.

[Edited on 18-12-2013 by AJKOER]

plante1999 - 18-12-2013 at 10:34

Or buying a Kg of alum for 7$ at the hardware store, it is used for pools. Bisulphate work better anyway...

Zyklon-A - 18-12-2013 at 13:25

I have used the thermal decomposition of aluminum sulfate, it works fine, except it's a pretty high temp.

DubaiAmateurRocketry - 18-12-2013 at 14:05

Heating copper sulfate to 600+ degree give SO3, or if you can get sodium persulfate, great, it works same way but with less temperature.

Heres a paper published by our lovely members on H2SO4 synthesis from SO3

Read it, and perform it nicely/carefully, SO3 and H2SO4 are extremely corrosive and you should take as much precautious and read more about it before you do it.

Zyklon-A - 18-12-2013 at 16:08

Except, I don't have (98-99%) conc. sulfuric acid to react with the oleum.

plante1999 - 18-12-2013 at 16:16

If you can find sulphur, making sulphuric acid is not really hard, especially if you can find platinized asbestos. If you can find nitric acid too. It is best to have an ounce of starting sulphuric acid, it is easier to make more with some.

P.S: If there is interest I could manage to make some platinized asbestos. Got "enough" asbestos, and a gram of Pt on hand.

Just found that:

[Edited on 19-12-2013 by plante1999]

[Edited on 19-12-2013 by plante1999]

AJKOER - 18-12-2013 at 16:53

Yes, Al2(SO3)3 is a relatively high temperature path to SO3.

However, I am investigating the possibility of a lower temperature preparation for SO3. First, I cite on properties of Nitrous acid (see ):

“On the other hand, many reducing agents are oxidised, the primary decomposition being: 2HNO2 = 2NO + O + H2O. Stannous chloride is converted into stannic chloride, sulphuretted hydrogen into sulphur, sulphur dioxide into sulphur trioxide.”

Also, per the same source, some important comments:

“The decomposition of a cold dilute solution [of Nitrous acid] follows the reaction 3HNO2 ⇔ HNO3 + 2NO+H2O, whereas stronger solutions at higher temperatures decompose according to the equations 2HNO2 ⇔ N2O3 + H2O ⇔ NO + NO2 + H2O. Other factors also influence the decomposition, such as agitation, surface area, and presence of nitric acid. “

There is also another 2004 published source, "Nitrosation Reactions and the Chemistry of Nitric Oxide", by D.L.H. Williams, mostly accessible online as a Google book at per Equation [10] and [11] on page 3 and Equation [35] on page 16, I surmise the possibility of the following under the appropriate reaction conditions/medium:

2 HNO2 + H2SO3 --> 2 NO + SO3 + 2 H2O

Or, removing one water:

2 HNO2 + SO2 --> 2 NO + SO3 + H2O

which is in agreement with Atomistry’s “2HNO2 = 2NO + O + H2O” acting on SO2 to reputedly form SO3.

Also, as 2 HNO2 = H2O + N2O3, assuming a nearly or totally non-aqueous condition, the implied reaction would be:

N2O3 + SO2 --> 2 NO + SO3

Interestingly, I am not alone in this last speculative delineation as to quote, albeit an old reference, from the “The Manufacture of Sulphuric Acid and Alkali, with the ...”, Volume 1, Issue 2, page 1021 by George Lunge (link: ) ):

“(2) In the atmosphere of the lead chambers it takes three seconds to oxidise NO to N2O3, or four minutes to carry on the oxidation as far,as NO2. Since it is unlikely that in the lead chambers molecules of N2O3 and SO2 meet so rarely that the former have time to oxidise into NO2, it is necessary to assume that N2O3 is that oxide of nitrogen which reacts with SO2 in the lead chamber. “

Here is another source (also dated) on the Lead Chamber process to quote from "The School Chemistry: A New Text-book for High Schools and Academies", by Elroy McKendree Avery, page 341 at .To quote:

"Although we have no reason to think that some of the reactions in the manufacture of H2SO4 are not simultaneous, we may, with propriety, trace them as if they were really consecutive. Several such explanatory series of reactions have been written out. One of these is herewith given, not as a didactic statement of what actually takes place, but as a theoretical exposition of what may take place.

(1) 4 FeS2 + 11 O2 = 8 SO2 + 2 Fe2Os, or S + O2 = SO2.
(2) 2 HNO3 + 2 SO2 + H2O = 2H2SO4 + N2O3.
(3) SO2 + N2O3 = SO3 + 2 NO.
(4) SO3 + H2O = H2SO4.
(5) 2NO + O2 = 2NO2, or 4NO + O2 = 2N2O3.

The NO2 and the N2O3 formed by these reactions are absorbed by the concentrated H2SO4 in the Gay-Lussac tower, combining chemically to form nitrosyl-sulphuric acid.

2 H2SO4 + N2O3 = 2H(NO)SO4 + H2O.

This nitrosyl-sulphuric acid is pumped back to the Glover tower, where it comes into contact with steam, whereby H2SO4 and N2O3 are formed.

2H(NO)SO4 + H2O = 2H2SO4 + N2O3".

So, an alternate synthesis of SO3 may be possible working with SO2 and HNO2 or N2O3 (or, more correctly, with the mix gaseous form NO + NO2) directly. In essence, this is a refined Lead Chamber process using efficient reactions to generate NO and NO2 (like with the respective reaction of Copper with dilute and concentrated Nitric acid) and react with SO2.

[Edited on 19-12-2013 by AJKOER]

Zyklon-A - 18-12-2013 at 18:49

Plante1999, yes I have a lot of sulfur, Can't afford (even a gram) of Pt.

Zyklon-A - 18-12-2013 at 18:55

Quote: Originally posted by plante1999  
Metal researcher, Or you could try the contact process, worked really well for me.

Plante1999, You got the Contact Process to Work???

plante1999 - 18-12-2013 at 18:57

I got it to work, but I did not repertoriate it online. The catalyst in the ebay link is perfect for that purpose, although you need fairly pure sulphur/sulphur dioxide if you don't want to poison the catalyst. You will need some time to build a suitable reactor. Rubber and latex can be present up to the catalyst, after which glass and metal only is recommended.

Zyklon-A - 19-12-2013 at 18:33

What kind of metal? I guess stainless steel could work, right.

plante1999 - 19-12-2013 at 19:09

Stainless is very good, even bare steel can be used if you don't mind a small amount of iron in your product.

Zyklon-A - 19-12-2013 at 19:25

Really???, I've always thought that ''bare steel" would corrode in the presence of Hot SO3, anyways, how about galvanized steel.

cpman - 19-12-2013 at 19:37

Galvanization would have little effect. Galvanized steel corrodes less in ambient conditions is the galvanic effect, where the plating prevents the iron from corroding by corroding first. It would not hold up that much longer than normal steel.

Zyklon-A - 19-12-2013 at 19:43

Of coarse I could clean the Zn off, with HCl, or something.;)

cpman - 19-12-2013 at 19:44

But then it would be no better than bare steel...

Zyklon-A - 20-12-2013 at 12:50

Of coarse, but the Zn might cause problems, and it does not offer much protection as it will be consumed, and turn into ZnSO4.