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Sauron
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Generating, Drying and Liquifying SO2 -> SO2Cl2 etc
What is the best substrate for generating SO2? Vogel and Merck Index are mum on this. Vogel just says "Go get a cyclinder" while Merck 12th says
nothing. I have not yet looked in Brauer, or Ullmann but I do not have high hopes.
Also I am soliciting advice on the drying train.
SO2 condenses easily at -10 C and freezes at -78. I want to liquify it and store it in lecture bottles with and without dip tubes.. I cannot purchase
SO2 where I am.
I want to use SO2 to prepare SO2Cl2 and SOCl2. Dry ice is readily available for cooling.
The no-brainer choice would be sodium sulfite or bisulfite. Generating with dil H2SO4 and scrubbing with conc H2SO4 are what come to mind. I am
looking for anything more efficient, if possible.
[Edited on 29-8-2008 by Sauron]
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not_important
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Silica gel or alumina could be used for drying, although H2SO4 works well. Also, if you freeze the SO2 and then allow it to just barely melt, I
believe water will remain frozen (possibly as a SO2-H2O mix) and so could be filtered off to give quite dry SO2.
I've always burned sulfur for making much SO2, for cost reasons.
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Sauron
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Cost is not really an issue and I'd just as soon not get into a DIY sulfur burner. SO2 from a burner is fine for making SO3 over V2O5 but that is not
what I am after.
Thanks for the input.
Brauer has no prep for SO2 but he does have drying procedure to use in prep of SO2Cl2 from SO2 and Cl2. He recommends conc H2SO4 for both gases,
washed seperately then mixed before passing through the reaction tube, which is a 6-bulg (or longer) Allihn condenser mounted vertically. The bulbs
are about half packed loosely with glass wool and about half of the remaining upper space is then filled with granular activated carbon. This setp
produces c.150 g sulfuryl chloride per hour. The product is quite pure and requires a single distillation only.
His setp using coarse camphor as catalyst is even simpler but the product requires two fractionations to rid it of camphor. IMO the GAC catalyst is
better.
[Edited on 29-8-2008 by Sauron]
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not_important
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Getting a sulfur burning that worked and keeping it working was trouble, but cost was a large enough issue to be worth the trouble.
The charcoal catalysed method did seem better to me as well. I've tried it, but used a simple plain tube fractionation column with a loose
alternating layering of glass wool and charcoal, in this case freshly prepared sugar charcoal.
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Klute
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Very interesting topic.
I have used the bisulfite method when trying to produce dimethyl sulfate via MeOH/SO2/CuCl2, and found it pretty satisfying: very controlable flow, no
excessiev frothing or foaming, and not too excessive volumes, although this wasn't on a very large scale.
Please let us know how it goes!
\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
-Alice Parr
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woelen
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I also used bisulfite + sulphuric acid for making SO2. The yield of gas was good, but I suffered from excessive foaming. The entire erlenmeyer and
even the tubes going from the erlenmeyer were filled with foam.
Klute, can you elaborate on your method of making SO2, which does not suffer from excessive formation of foam?
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Sauron
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Yes, please, Klute, we are all ears. Kindly let us know all the details of your SO2 prep.
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smuv
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I have used sodium metabisulfite and acid in the past to generate small amounts of SO2; no problems with foaming but this was all on a small scale.
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kilowatt
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If you can do high temperature (around 1200°C or a bright yellow heat) a mixture of coke or coal with gypsum or gypsum and silica will do. It can be
cast into pellets and loaded into a steel or refractory retort. With excess carbon (more than 4:1 carbon to CaSO4 molar) calcium sulfide is formed
instead.
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Sauron
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@KW I have no idea what you are on about. We are talking about generating SO2 chemically. Smuv mentioned decomposing sodium metabisulfate thermally. I
looked at that and related thermal decompositions and concluded they are uneconomical and rather low yield.
Please explain. Assume I know nothing which is not overstating the case.
I am just after a nice chemical process to make SO2 gas I can dry then condense with dry ice-acetone to bottle in LBs as vapor over liquid. No
semi-industrial processes please.
If I can make 500 g liquid SO2 in 8 hours I will be happy. This is only about 8 mols. Enough for a standard lecture bottle IIRC. I think those are
440 cc and SO2 has a d of c.1.5. A quick look at old Aldrich catalog will remind me how much is normally in a LB. (Answer is 454 g so about 300 ml, LB
is 2/3 full.)
[Edited on 30-8-2008 by Sauron]
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Magpie
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The idea of having SO2 on tap in a lecture bottle has intriqued me for some time although I have no immediate plans for its use. I know that the wine
industry in my locale buys or rents small cylinders of SO2 on a regular basis. It perturbs me that I could probably not just buy one of these
although I admit not having tried. I'm just suspecting that one would have to be in business to buy one.
This is putting the cart before the horse, but Sauron, where do you purchase lecture bottles?
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ScienceSquirrel
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I have used liquid liquid sulphur dioxide as a reaction medium back in my professional days.
It has a high boiling point so the gas normally comes in a little bottle a bit like a butane gas cylinder but with a small brass fitting to go on top.
Something like this;
http://www.sigmaaldrich.com/catalog/search/ProductDetail/FLU...
[Edited on 29-8-2008 by ScienceSquirrel]
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Sauron
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Aldrich sells mild steel and stainless steel lecture bottles. If I recall the mild steel bottles have a choice of thread sizes. They also sell valves,
regulators if you have to get fancy, holders and carriers, systems for connecting LBs in series and so on.
In this country I have found no local source. The Thai industrial-gases company does not sell lecture bottles (filled or emptry) though they will fill
them for you if you have the bottles. But they cannot do that for SO2 due to MOD restrictions.
Photo from Aldrich attached, mild steel LB 3/8" NPT
In USA you probably have a number of choices as to suppliers. Note that lecture bottles are not same as "sample boms" the latter normally have
threaded necks at both ends although sometimes they can be had flat on bottom. (Lecture bottles have a rounded bottom and so can only stand erect when
in a holder.) In general lecture bottles are less costly than sample bombs.
Aldrich also sells mild steel Kilo Lab cylinders in larger sizes than 440 ml LBs.
My intention is not long terms storage but merely making what SO2 I need "JIT" (Just in Time" If using it as a solvent, no problem, a Dewar will do.
If using it in a reaction it is better to put it in a LB and control the flow, so a constant flow rate is attainable, something just about impossible
to get out of a generator.
Under these conditions mild steel is fine. Bone dry SO2 does not attack mild steel. If I wanted to keep a LB of it on the shelf I would be inclined to
put it in a SS LB even though they are a lot costlier, as I do not fancy a SO2 leak.
But if I can generate 500 g a day why should I need to store any on the shelf? That's just asking for trouble.
As an aside, SO2 dissolves in methanol to extent of 32% w/w (according to Merck).
ScienceSquirrel, I am looking at a 13 ywar old Aldrich catalog and they still listed SO2 in 454 g lecture bottles. At that time this was $150.
Vogel describes SO2 being available commercially in heavy walled glass bottles with a valve on top.
I am quite certain that SO2 is available commercially/industrially in cylinders, as it is widely used in industry and agriculture, for example for
preserving fruit, bleaching textiles, and so on. It is almost certainly available in industrialized countries in lecture bottles. In this country it
is proscribed for no good reason that I can see.
[Edited on 30-8-2008 by Sauron]
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Formatik
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SO2 preparation
Gmelin in S[A] and S[B] covers a variety of reactions for SO2 formation. Some basic information: By dry heating of sodium dithionite Na2S2O4 at
190ºC there is suddenly a large amount of SO2, but the reaction occurs exothermically and explosively (Z. anorg. Ch. 191 [1930] 340/81, 342). SO2
will form by thermal decomposition of sulfites: Z. anorg. Ch. 139 [1924] 261/92, and pyrosulfites as well as by heating of their solutions. For
suitable preparation: by the addition of acids onto sulfites or aqueous sulfites. More about this under the sulfites themselves. There are other
methods covered ie, decomposition of sulfates, H2SO4, sulfide roasting, reaction of S with metal oxides, etc. but the reaction of sulfites seems to me
to be most suitable for the lab preparation.
I've used several grams of a metabisulfite and hyposulfite mixture then letting moderate HCl drip in through a separatory funnel to generate SO2 in
the sulfuric acid thread, but eventually had violent blow offs of the cork, maybe starting out using the sulfites in solution and better stirring
could have avoided these.
[Edited on 29-8-2008 by Schockwave]
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Klute
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I dripped a conc. solution of sodium metabisulfite into 50% H2SO4 with good stirring. Maybe the reverse addition causes foamign because bisulfite is
in excess at all times, and the SO2 is evolved on a larger surface/volume, where as with excessa cid the recation si very quick and somewhat located.
But obviously after a while the whole solution is bubbling, but no excesisve foam (hardly more than 1/2 cm at max.)
Here is the thread wher ei decribed the (failed) attempt at preparing (MeO)2SO2 with SO2/CuCl2/MeOH.
A attempt at Halfapint's DMS synthesis
the resulting waste water still contains appreciable amoutns of SO2 (saturated). Heating it to reflux should expel a certain amount of SO2, and the
solution could then be kept as a reducing agent to quench other oxidative wastes before disgarding the two.
[Edited on 29-8-2008 by Klute]
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panziandi
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I would use sodium metabisulphite, very cheap commercial chemical with high quantity of SO2 in it. I would add reasonably concentrated H2SO4 to it,
that way minimising volume of wastes. Dry by a wash bottle of H2SO4 then into a dry ice-acetone dewar condenser with an adaptor at the bottom to lead
the liquid into the lecture bottle (chilled in dry ice) then just close it off once filled suitably.
I was looking at those lecture bottles myself but not for SO2. I was not sure about the threading, you just literally thread on a valve once filled
with your liquified gas and the valve acts as the regulator? It looks like that from the pictures etc. Although the entire set up is a little off
budget for now until my student funds come through!
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ScienceSquirrel
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As you say there are lecture bottles and larger cylinders of sulphur dioxide on the market.
The 'tins' of sulphur dioxide that I referred to are still available. I was not doing a huge run of experiments using sulphur dioxide so a few tins
were enough.
I am surprised that sulphur dioxide is so restricted in Thailand. I would have expected it to have been fairly freely available.
I would guess that there is a substantial agricultural and food processing sector and round here they tend to throw sulphur dioxide in everything.
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Formatik
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| Quote: | Originally posted by panziandi
I would use sodium metabisulphite, very cheap commercial chemical with high quantity of SO2 in it. I would add reasonably concentrated H2SO4 to it,
that way minimising volume of wastes. Dry by a wash bottle of H2SO4 then into a dry ice-acetone dewar condenser with an adaptor at the bottom to lead
the liquid into the lecture bottle (chilled in dry ice) then just close it off once filled suitably. |
For a freezing mixture, I would use alcohol/CO2 mixes which should stop just short of the freezing point of SO2 (from the freezing mixture thread), also better is that alcohol is more readily available.
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Sauron
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Aldrich's Kilo-Lab sylinders re larger sizes 18 and 90 L mild steel and I believe rated at 1800 psig.
Their smaller steel storage are called Sure/Pac and run from 2.2 L down to 25 ml I think.
They have only a few sizes of stainless steel double ended sample bombs, I think largest is 500 ml to approx same as a LB (440 ml)
The SS lecture bottles they were showing in their online catalog last year are now gone. Sole remaining Aldrich LB offering is mild steel.
I have a lot of material about other sample bomb manufacturers in USA, such as Parker and Swagelok. Some single ended types are made with flat bases
in SS.
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Picric-A
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If you have easy acess to conc sulphuric this reaction works extremly well.
Simply add pices of copper to a flask followed by conc sulphuric acid and simlpy heat to produce a steady stream of SO2, quite dry. This method works
well when you have plenty of drain opener. Of cours it is pointless when using it to make sulphuric acid via contact process... 
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Klute
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Funny, I had a pretty bad view of this reaction: it was very irregular, violently bumping at times, and hard to control (can't add more Cu without
opening the setup and getting gassed).
I suppose on a very small scale it can be practical, but I would hardly recommend that to produce 8 moles of SO2 
\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
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Picric-A
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I find it very smooth and easy... hmmm what size copper do you use? powder or granules?
If you add an exess of Cu to the flask then add the H2SO4 with a dropping funnel it can be easily monitored and topped up.
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Sauron
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Sorry, kid, I don't muck around with drain cleaner or battery acid, just reagent grade H2SO4. I'm a chemist not a plumber or an auto mechanic. And
this thread has nothing to do with making sulfuric acid.
[Edited on 30-8-2008 by Sauron]
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Klute
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Granules, from finely cut Cu wire. I wanted to get some SO2 and coulf have used with some CuSO4, but I finally stuck to metabisulfite and made CuSO4
seperatly.
\"You can battle with a demon, you can embrace a demon; what the hell can you do with a fucking spiritual computer?\"
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panziandi
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Sauron: I think the confusion about the contact process was from further up the board when somebody posted about a sulphur furnace which is not a
suitable method for you. He didn't mention drainer opener from what I can see just said "if you have access to plenty of sulphuric acid" which I
assume you do.
To be clear Sauron wants a chemical method of making clean SO2 gas quickly in the lab not industrial methods just methods which work and a quick and
easy. He then wants to dry and liquify and store this gas in a cylinder.
I'd say acid + sulphite/bisulphite/metabisulphite. I think the last is easier to get in larger quantities cheaply. Copper may work, I read it does, I
haven't tried it but if I was doing this I'd go with teh acid+sulphite method myself for convenience.
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