H2SO4 by the Lead Chamber Process - success

I was going to hold on to this a bit further - until I have more observations to report - but I decided otherwise since the more that try the process, the more improvements might be invented - and many of you may have suggestions and ideas to optimize the process.

Also, I can't resist the temptation of bragging about finally finding a successful, simple way of making H<SUB>2</SUB>SO<SUB>4</SUB> with easily obtained tools and chemicals...

The Lead Chamber Process, invented in 1746 by the Brit John Roebuck, was the first feasible industrial manufacturing process for H<SUB>2</SUB>SO<SUB>4</SUB>, and wasn't replaced with the contact process (using a Pt catalyst to oxidize SO<SUB>2</SUB> to SO<SUB>3</SUB> until the first half of the 1900s. Lots of historical information exists online, I won't go into the historical aspect more than strictly necessary.

In the lead chamber process, 7 part sulfur (note 2) is burned together with 1 part sodium or potassium nitrate inside a lead-lined chamber (note 1) with water covering the floor. SO<SUB>2</SUB> is generated in abundance together with lesser amounts of NO from the saltpetre. Over time (several hours in my experience) the NO catalyses the oxidation of the gaseous SO<SUB>2</SUB> to the trioxide SO<SUB>3</SUB>; which combines with the water on the floor, as well as with water vapour (note 2) inside the chamber, to form dilute H<SUB>2</SUB>SO<SUB>4</SUB>. The reaction mechanism is described by the following, unbalanced reactions:

(a) 3S(s) + 2KNO<SUB>3</SUB>(s) --> K<SUB>2</SUB>S(s) + 2SO<SUB>2</SUB>(g) + 2NO(g) ;sulfur + KNO<SUB>3</SUB> reaction
(b) S(s) + O<SUB>2</SUB>(g) --> SO<SUB>2</SUB>(g) ;combustion inside the chamber
(c) 3NO(g) + 3/2O<SUB>2</SUB>(g) --> 3NO<SUB>2</SUB>(g) ;spontaneous at NTP
(d) 3NO<SUB>2</SUB>(g) + 3SO<SUB>2</SUB>(g) --> 3SO<SUB>3</SUB>(g) + 3NO ;catalyzed oxidation
(e) SO<SUB>3</SUB>(g) + H<SUB>2</SUB>O(l) --> H<SUB>2</SUB>SO<SUB>4</SUB>(aq) ;absorption

In (a,b) 1 part of the sulfur combined with the nitrate during the combustion, and the other 6 parts combines with oxygen from the air inside the chamber. (c, d) constitute the catalyzed step.

Now, the "1 part nitre to 7 parts sulfur" ratio is, according to the sources I've read, the one that was commonly used in plants at the time. I'd guess it was chosen to save on the amount nitrate needed while still making the reaction go fast enough. The nice thing here is that the amount of nitre used only influences the rate of the reaction, not its completion. Lesser amounts of nitre makes (c, d) proceed more slowly, larger amounts make them faster. The nitrate (or rather the NO produced when combined with sulfur) acts as catalyst, not as sulfur oxidizer. Note that the oxygen content of the chamber must be in excess to the sulfur burnt for (c, d) to have oxygen to draw from.

Armed with this knowledge I proceeded with trying out the process on a much smaller scale.

1) The lid to a 25-liter fermentation tank made of PP was fitted with a glass pipe going through it that when the lid was fitted ended about 50mm from the bottom of the tank.

500ml of deionized water was poured into the otherwise empty tank.

A small glass bowl with KNO<SUB>3</SUB> in the bottom was placed in the bottom of the tank.

Solid pieces of sulfur were prepared by casting purified sublimed sulfur to a puck shape in a can, then crushing the puck.

To initiate a burn, a piece of solid sulfur was placed on the bed of KNO<SUB>3</SUB> and set on fire with a powerful butane lighter. Then the lid was put on. Once molten, it burns nicely in a puddle on top of the KNO<SUB>3</SUB>. When it gets warm enough after about 30 seconds, the KNO<SUB>3</SUB> under the sulfur / mixed with the sulfur will start decomposing, and a black powder like burn will to self-perpetuate, going on until all the sulfur is burnt. The whole reason for the pipe for those that can't guess it, is so that the SO<SUB>2</SUB> + NO rising upward from the burning sludge in the bowl won't start to leak out until the chamber is filled; I wanted to really fill the chamber.

Now, this deviates from the 1/7 ratio in the original process and seems like a horrible waste of KNO<SUB>3</SUB>, but I have 4 reasons:
1) The chamber size is very small and has limited oxygen. Thus a stochiometric amount of KNO<SUB>3</SUB> will make all the oxygen for (a, b) come from the KNO<SUB>3</SUB>, not the chamber air -- leaving the oxygen of the latter intact for reactions (c, d).
2) It makes (c, d) go at a faster rate.
3) It's easier, and I'm very lazy.
4) I've got 70kg of the stuff sitting in my wardrobe, and can get more very easily.

After the burn, all that's needed is to wait a few hours. The cloudy gas from the burn will clear up as the SO<SUB>2</SUB> inside the chamber is oxidized to SO<SUB>3</SUB> and absorbed into the water. If the chamber was hermetically sealed, it would collapse as the gas volume inside decreases. I've tested the process with a plastic Coke bottle which was sealed, and it imploded slowly over a few hours. After the waiting period, the lid is removed, and the NO/NO<SUB>2</SUB> allowed to vent. Then the process is repeated.

I had done over 10 burns with my first batch when the glass bowl used as burner cracked from the heat, spilling KNO<SUB>3</SUB> into the dilute H<SUB>2</SUB>SO<SUB>4</SUB>. Before thinking, and quite pissed off, I flushed all the fluid down the toilet to start over using a ceramic bowl instead. I should have saved it for analysis -- all I can say is that it fizzled a lot when coming into contact with whatever salt deposits are always building up in the the toilet bowl. Normally I remove the deposits using HCl -- the HNO<SUB>3</SUB> from the KNO<SUB>3</SUB> in the H<SUB>2</SUB>SO<SUB>4</SUB> seemed to work just as well... I have a new batch going and have done 2 burns in it so far.

I'll report the progress.

----
note 1: Lead being the only cheap material resistant to H<SUB>2</SUB>SO<SUB>4</SUB> available at the time.
note 2: Yes, I know I'm mixing American and British spelling, and no, I won't stick with one of them. I prefer parts of both...

If I got it right, you didn't mix the two components to keep reaction speed down? Why not make solid S/KNO3 cakes in an iron can? Maby hang it below the lid to avoid the heat (making sure the can doesn't melt/react..).

Keep up the testing!

[Edited on 13-11-2004 by frogfot]

H-O-L-Y C-O-W !!!

No pictures. Is it needed? It's a big plastic bucket with a lid, a hole in the lid with a glass pipe shoved through, a food bowl with KNO<SUB>3</SUB>, a bit of water at the bottom... aaah, I suppose I could take a picture later...

About dissolving SO<SUB>2</SUB>: Not sure there. Have only tried it with very small amounts of water. Wouldn't the SO<SUB>2</SUB> so dissolved carry over to the next burn, making the water already saturated provided the burns take place at intervals close enough to make the autodecomposition of SO<SUB>2</SUB>(aq) insignificant? I too would love to know if the catalysis takes place in aqueous soln. as well. Self, I suspect the formation of nitrosylsulfuric acid HNOSO<SUB>4</SUB>.

Another observation

Congratulations Axehandle!

I suppose one could get away with leaving out the nitre, having all the H<SUB>2</SUB>SO<SUB>4</SUB> come from autodecomposition of H<SUB>2</SUB>SO<SUB>3</SUB>, but I think the process would be horribly inefficient -- days instead of hours, and very dilute acid. BTW, the reaction
S + KNO<SUB>3</SUB> --> SO<SUB>2</SUB> + KNO
also takes place, AFAIK. I don't know the extent of the
3S + 2KNO<SUB>3</SUB> --> K<SUB>2</SUB>S + SO<SUB>2</SUB> +2NO
reaction, only that it <b>does</b> take place. The "cloudyness" clearing up inside the chamber over a couple of hours combined with the fact that the fluid does <i>not</i> smell of SO<SUB>2</SUB> upon opening the container is proof.

Oh, and most nitrates would probably work. In the old days, NaNO<SUB>3</SUB> was used. Perhaps even NH<SUB>4</SUB>NO<SUB>3</SUB> could substitute .


[Edited on 2004-11-14 by axehandle]

Was more of a "thinko" than a typo --- didn't mean rotten eggs at all. Edited.

Hey Axehandle

It seems to me that it may be possible to produce oleum by the chamber method
if the chamber material is compatable with the fuming sulfuric acid produced . It also seems possible that the process could be made to run continuously by a forced flow of the the sulfur combustion gases into the chamber . A paddle stirrer could be used to maintain a cyclonic flow of the gases in something like a large glass water carboy , which would centrifuge the condensing fog of acid droplets against the walls and aid the speed of the reaction and separation . The sulfur could be preburned as a sulfur lamp in a separate chamber , where the sulfur is melted in a pot and burned on a glass fabric wick , the combustion air supplied to the sulfur lamp by a small pump like an aquarium pump .
If a small chamber equipped with a spark plug was placed in the air line to the sulfur lamp , and a continuous arc maintained in the airflow , there may be a sufficient catalytic amount of nitrogen oxides produced to maintain the process . This would have to tested and it may require several spark plugs driven from a sign transformer to produce the needed amount of nitric oxides . By regulating the moisture content of the incoming air , the process can be controlled ,
all theoretically of course

By such a scheme , the only precursors required for oleum would be sulfur , air ,
and electricity .

factors to be considered

Yeah, you can _just_ boil the water out. It's just that it takes a lot of energy. The process now used adds SO3 to water/acid mix and can make anhydrous acid without additional heating (and the associated product loss)

To check out the strength of your acid, reffer to this thread.
http://www.sciencemadness.org/talk/viewthread.php?tid=5817#p...

Nitric may be made with sulphuric of less than 96% concentration. The only thing is that the distillation will need to be run at a higher temp, will produce acid with some water in it (hence higher temp needed), in addition to these two points, you will have a lower yield as a result of the greater amount of nitric being decomposed at the higher distillation temp.

That said, I've successfully made nitric from boiled car battery acid + nitrate salts. Though it still wasn't as potent as that produced by the distillation of comercial 70% with comercial 98% sulphuric.

ps - don't wear too much cotton (t-shirts, jeans etc)

and ,from the way which axe have made, what happen to K2S? my worry is which some of it can be oxidised to more SO2 and K2O by the saltpeter and some of this can fall into H2SO4, impurifying it... any ideas?


EDIT: tupence_hapeny , great document.. has anyone tried this?

Bromic: i've seen another great document which you have posted at another thread from catalytic oxidation of SO2(aq) in presence of some MnSO4 ...

what about build a *somewhat* different and more expensive lead chamber?.. replacing the KNO3 by KMnO4 (i'm sure which at least some MnSO4 are produced) and fire it inside a chamber with temperature and pressure control (to insure full absorpition of the SO2 generated)...

unfortunatelly by this line of thought , the sulfuric acid whcih can be produced will be very impure , expensive and diluted... but is an idea

[Edited on 20-6-2007 by Aqua_Fortis_100%]

[Edited on 20-6-2007 by Aqua_Fortis_100%]

as far as i've seen H2SO3 doesn't convert on its own. i think if it did we'd all be making our own H2SO4

and why would i have to add more HNO3? the reaction works just fine with HNO2 also. in fact that may end up doing the majority of the work. thanks for the input.

i have a couple of problems with it though. i am skeptical its going to get much gas exchange with simple bubbling, so i was thinking i would use an aquarium airstone that produces very fine bubbles. but the problem is i'm not sure where i can get one that will hold up in concentrated sulfuric and nitric... or maybe theres another way to get good exchange...

also i'm not sure what to use as containers. something fairly tall would definitely be better but is has to have a sealed lid, so glass is not an option. my first thought was PVC but i'm not sure how well that would hold up in those acids. if it can handle them i might even get clear PVC. if all else fails i could use some SS 316 pipe, i can weld it too... but in very big diameters that shit is expensive!

well i checked ebay... 5 ft of 2 1/2 inch diameter SS 304 going for $60 plus $20 shipping... not too bad i suppose. 304 should work too shouldn't it?

[Edited on 4-11-2007 by 497]

revised version

so i decided a batch process would be much more effective. coments?

Some months ago I was just experimentating with this interesting subject.. The first experiment I did was the described in a link posted above ('pop bottle process') . I've used a PETE 2.5 L pop bottle , some sublimed sulfur , KNO3 , 10mL or so of water, and a encurved teaspoon adapted to the lide of the pop bottle.

This is a extremely mess process, because you often became exposed to nauseous SO2. I simply have putted the KNO3 in the encurved spoon and heated with until melted,and the adding the S8 (I've found that is much better doing this than heating both simultaneously,because less sulfur is just burned in open air and hence less is wasted(since when mixed the sulfur ignites pretty fast)) which in turns gave a red-brown melt and ignited instantaneously (but smoothly ) and quickly puting this in the pop bottle.. I did this 10 times(waiting ~30 mins between each burn,and letting some O2 come into the bottle), but sometimes the sulfur-KNO3 melt have fallen in the solution and causing more mess..

after this , I've filtrated the suspension of sulfur in the acid misture .. then I used the procedure described in a link posted by tupency h. wherein a cooled (-10*C) solution of H2SO3 + O2 can yield H2SO4.. So I've put the filtrate in a container and this in a salt-ice bath for 20mins.. when I back to the place where the solution were standing, I've noted a white precipitate (KNO3 from the mess or any salt formed in situ like KHSO4, KHSO3, etc ¿¿¿)..

This gave me a great grief and foul thinkings

so I dumped the contents on the cement floor , in backyard..and the stuff made some bubbles and the caracteristic 'whoooosh' from acids on the things.. So , at least this gave me some happy thinkings.. (however this can also probebly by due by the H2SO3)...

Quote:

Originally posted by Aqua_Fortis_100% Some months ago I was just experimentating with this interesting subject.. The first experiment I did was the described in a link posted above ('pop bottle process') . I've used a PETE 2.5 L pop bottle , some sublimed sulfur , KNO3 , 10mL or so of water, and a encurved teaspoon adapted to the lide of the pop bottle. ...

Yes that's the link I'm refering in the post. I've used the spoon solely because in the time I did the procedure I didn't have ANY copper/iron wire or endcap laying around, and lazy to go to the local (6 km far from my house ) hardware store... So I've did the necessary improvises..

[Edited on 14-11-2007 by Aqua_Fortis_100%]

Quote:

Originally posted by Aqua_Fortis_100% Yes that's the link I'm refering in the post. I've used the spoon solely because in the time I did the procedure I didn't have ANY copper/iron wire or endcap laying around, and lazy to go to the local (6 km far from my house ) hardware store... So I've did the necessary improvises.. [Edited on 14-11-2007 by Aqua_Fortis_100%]

Upscaling...

This Drawing is my new backyard chamber..(I dont have a cam at the momment, So I did a fast drawing)..This was did quite a some days, and didn't post before together with the earlier posts because of the hurry I'm in..

I've did some simple calculation on gases before the pratice and will present below. Please, if anyone find in my calculations some weird or wrong thing, feel free to tell and correct me..

(I)

Descripition:

PETE bottle is a fairly resistant material against many diluted and weak acids, I often store filtrated battery acid in it without any problem, and also is a fairly inexpensive material to get(usually free if you like drink or 'hunting' in the weird and funny neighbourhood trash).. That's the reason I've did chosen and used this material in my experiments.

My chamber consists of a (more or less irregular ) serie of pop-bottles straight on the floor (the generator are also in the same position..My drawing mess up in this also ; be aware to not think the pop-bottles are upside-down in a weird position )and with some wet cloth on it ,( to help cooling the inlet gases). Each of them being connected to the other by means of 8 cm piece of common aquarium tubing and with the help of hotmelt glue.

At one extreme of the chamber, the aquarium tube is connected in a side of a empty kerosene metal can(with some PTFE, to give good seal), which in turns holds a pierced cork stopper with generous amounts of PTFE around it ( to both protect the cork stopper and to improve seal) with an radio antenna Al tubing which is jointed together with a old refrigerator copper tubing (PTFE is used also here, since the temperature, IMO, isn't that great at the point). The copper tubing is connected in the Rojek lid of my 'reaction vessel' ( a tomato 'tin' can ) and some plaster of paris (I just used this because is the most common and the only that I know somewhat..I've great problems with sealing and soldering tubes to vessels (speciallity the first),because the hardware store here recently don't appear to be an friendly place to visit..high prices and very few interesting things). The edges of the tin can were wrapped with some Al foil, to help keep the lid in the correct place(the rojek lid seem to have tiny amounts of a plastic material in it..bad news) and the lid pressured in the place... The holder of the reaction vessel in the drawing is a iron type paraphernalia, but in my experiment was simply 2 common bricks and the alcohol burner under the tin can...

The reactants were impure (CaCO3 - gardening) sulfur ,tap water (10mL in each pop-bottle) and double saltpeter (NaNO3/KNO3,1:1 - without wax additives, which were removed-, which I just considered as KNO3 to dont increase the trouble..)
..

(II)

Consulting Axehandle rxns an overall one can be made, based on the natural sulfur allotrope...

S8 + 16/3 KNO3 --------> 8/3 K2S + 16/3 SO2 + 16/3 NO


S8 => 32.1*8 = 256,8g
16/3 KNO3 => (16/3)*101.1 = 539.2g
------------------------------------------
8/3 K2S => (8/3)*110.3 = 294.1g
16/3 SO2 => (16/3)*64.1 = 341.9g
16/3 NO => (16/3)*30 = 160g

========================

(III)

So, the sum of gaseous products is NO + SO2 , what means 16/3 + 16/3 mols => 32/3 mols of gas

arbitrarily (because neither of my thermometers are reliable to measure) considering the final temp (after passing the last pop-bottle and venting to outdoor) as 30°C, PV=nRT can be used to determine the final volume of all gases in the system:

1*V = (32/3)*0.082*303
V= ~265.02 L

======================

(IV)

Next step is calculating the total volume of all pop-bottles connected to each other...(desprezing minor volumes like the tubing and can volumes,water, etc)..

pop-bottle type: PB Amount: Volume(L):

1.5 L........................3.....................4.5

2.0 L........................23...................46

2.5 L........................1.....................2.5
Total PB: 27 Total Vol: 53

So, by dividing the total vol of the chamber by the arbitrary value found at (IV) we will find the theoretical necessary amount of reactants needed to fill all the chamber:

53L/265.02L = ~ 0.2

so,

16/3 SO2 * 0.2 = ~ 1.067 SO2
16.3 NO * 0.2 = ~ 1.067 NO

Now looking also (II):

If to produce 16/3 moles of SO2 we need 256.8g of S8, what is the amount of S8 needed, if we need only 1.067 mols of SO2 ? AFAIK: x = ~51.4g S8

Doing a similar calculation with the KNO3 we will find: ~ 107.87g KNO3..

So again arbitrarily, I've just cutted the amounts aproximately by half: 25g S8 and 55g KNO3 by shoot...

the results of my experiments I will post tomorrow, because its getting late here.. (the results were very weird at principle..but just funny)

[Edited on 14-11-2007 by Aqua_Fortis_100%]

@497, yes your method seems to have much less labour than my one..but you are using HNO3 and this isn't very much OTC in most countries, because of its very interesting and 'popular' properties/uses.. .. Additionally most people here and in other places wants H2SO4 actually to make HNO3 , not the opposite(well..the lead chamber process can be used just for fun, like my project, or then for real production of H2SO4, which is very hard to worth, because which sulfuric is still a widely avaliable chemical, even if will not be OTC in concentrated form..also is difficult to have near 100% no losses in HNO3 and hence , at a given time you will need to replace some, more on that latter).

Ironically, the initial results of my 'lead chamber' were... NITRIC ACID ! While I've just carefully watching the heating of the rxn vessel, large brown/red clouds evolved during the start and filled the kerosene can , the first and 2nd pop-bottles..I´m very sure that this stuff is NOx, not only by their colour but because also of it foul and toxic smell.. after, when the rxn vessel started to evolve white fumes of SO2, the improvised sealing on the rxn can failed and started to leak out..what forced me to remove the can immediatelly from the heat source and allowing to cool down..inside the can a black boiling mass..

This is weird for me, because the sulfur tends to react in open air with KNO3 in a manner completelly diferent: burning imediatelly and evolving SO2, and I did tried this many times.. but I just thinked before that the KNO3 itself are able to give some oxygen to S8 and start a oxidant/combustible type reaction and burning without O2..,But inside the can the only thing happened was the boiling of the mass (without fire..even when the lid was removed).. So my next try would be adaptating a hose from the aquarium pump to the reaction vessel and allowing lo force some air along it..this will prevent this mess to happen , fire the mix , reduce the nitrate consumption and also give a more homogeneous distribution of the gasses along the bottles..But also maybe requires more volume to work properly, without leaking out too much gasses before they react (which means more bottles attached) or lower amounts of reactants per shoot..

well why don't you just use that nitric you got in my process??? but really you have a point, nitric isn't the most OTC.... one reason i'm working on a nitric acid producing apparatus, see: https://sciencemadness.org/talk/viewthread.php?tid=1518&...

and as for the surface area issue, i agree the PETE bottles will have more. but i think that could be solved by agitating the water in an HDPE bucket. either way you're having fun, and thats what really matters.

another thing, i don't think you really need to heat the reaction KNO3/S8 reaction. from what i've read earlier in the thread all you need to do is light the mixture with a lighter and it burns just fine after that. 3S + 2KNO3 --> K2S + SO2 +2NO, etc.

anyone know a good way to measure the concentration of nitric acid? i have a pH/conductivity meter, but i don't trust it's accuracy above very dilute acid.

Could you bypass the issues of large volumes by liquefying the SO2? It boils at -10C or 34 PSI at room temp. Hopefully it can actually decompose in liquid phase. It would need to be contained in glass to decompose it with light. Shouldn't be a problem in large borosilicate tubing or the like. That would be pretty awesome if you could just set a tube of liquid SO2 out in the sun (or 150 watt metal halide that I happen to have ) for a few hours/days/weeks and come back a have a tube full of SO3. Maybe even use a little parabolic reflector to speed things up. Somehow I doubt it would be that easy.

Also I've found that 32%H2SO4 + 50%H2O2 reacting with copper metal produces quite a lot of nice clean SO2 (maybe some O2 too) and quite a bit of heat, that tends to start to boil it after a while.

Edit: I found pressure specs for borosilicate tubing, 38 mm dia 4 mm wall can handle 200 psi, so there should be no problems with pressure as long as the end caps can be affixed strongly. Having a means of getting the liquid in and out that is resistant to SO3 might be a challenge though. Or you could just not worry about it and break the tube open when you get the SO3 out.


[Edited on 16-2-2008 by 497]

Hey, anyone got any I2 laying around? I just realized that you could use part of the iodine-sulfur process to make good concentrated H2SO4.

I2 + SO2 + 2 H2O -> 2HI + H2SO4

Then recycle the iodine:

2HI -> H2 + I2

I also found out that liquid sulfur reacts with SO3 to make SO2... not good. Hopefully its not the case for solid sulfur.

[Edited on 17-2-2008 by 497]

Quote:

Originally posted by 497 Hey, anyone got any I2 laying around? I just realized that you could use part of the iodine-sulfur process to make good concentrated H2SO4. I2 + SO2 + 2 H2O -> 2HI + H2SO4 Then recycle the iodine: 2HI -> H2 + I2 I also found out that liquid sulfur reacts with SO3 to make SO2... not good. Hopefully its not the case for solid sulfur. [Edited on 17-2-2008 by 497]

You're referring to the Bunsen reaction for the first part. It's one way of making aqueous hydrogen iodide in the lab.

The reaction is an equilibrium, too high of a concentration of the acids drives it towards I2 + SO2 + H2O. This includes distilling the HI-H2O azeotrope away from the mix.

In the IS cycle to produce H2, the separation is accomplished by using an excess of I2 and some starting HI to form two phases, HI-I2-H2O and H2O-H2SO4. The excess iodine, plus an excess of water, is used to help drive the reaction to HI + H2SO4.

In that case it typically is run at 110 to 130 C, with cooling as it is exothermic.

I'm attaching part of a material balance sheet for the Bunsen section of a ISH plant.

section 115 is the feed into the Bunsen reactor, run under a bit of pressure.
116 is the flow out of the reactor into a phase separator
117A is the off gases
118A is the H2SO4 phase
119A is the HI-I2 phase

Note that both acid streams are fairly dilute, the H2SO4 also contains a little SO2 which is no big deal. However the acid concentrations, plus the large of iodine used, might discourage you; this is especially true in the USA and Oz where the element is contraband.