RogueRose
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Vanadium Pentoxide V2O5 as catalyst for contract process - how to use as substrate?
OK so the contact process of making H2SO4 looks fairly doable with the pressure level of 1-2 atm but I'm really confused at the 450C / 842F temp at
the 1-2 atm level.
From what I have gathered, the V2O5 is in the chamber at 450C and 1-2 atm and then the SO2 and excess O2 is passed through yielding SO3.
Now all of that seems doable as long as some kind of SS is usable for the pressurized vessel. What I'm confused about is how to get the 450C without
going well above the 2 atm pressure mark.
So could the vessel be heated to 450C and have the SO2 and O2 pumped into the vessel, pass over the V2O5 and then out another one way valve (that
opens at 1-2 atm to release pressure). Then the pump pumps in the two gasses till it reaches the release pressure and out flows the SO3 (and O2
probably).
what I'm wondering is the best way to use the catalyst powder as it is pretty fine. I could probably place it on super fine SS mesh to hold thin
depths of the powder and place multiple levels of screens with the powder on top - giving more surface area. It would seem that there should be a
much better way to coat some metal surfaces with this - but if it gets really expensive then that could be prohibitive. It is about $13/kg for very
fine powder but I could see coated plates being much more $$
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Magpie
lab constructor
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Mood: Chemistry: the subtle science.
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http://www.sciencemadness.org/talk/viewthread.php?tid=8923
The single most important condition for a successful synthesis is good mixing - Nicodem
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violet sin
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are you planning on using V2O5 directly on the SS screen? or maybe dilute it on some kind of ceramic substrate????
traditionally it is processed into ammonium metavanadate sol, then evaporated substrate and decomposed for a fine dispersion.
there is a lot I don't see working well with this line of reasoning. but that is just me. like under pressure? just try it in a quartz tube, no
pressure. how are you generating the SO2
try to find info on others who have attempted this. and Mgapie beat me to it
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RogueRose
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Thanks for the link, that looks to be some good reading!
As far as the V2O5 on a SS screen, that was just an idea as it might somewhat impregnate into the small holes and then have a fine layer on top. When
I say screen I'm talking about very fine mesh from 40-120 depending upon how fine the pentoxide is.
As far as the pressure, do you think 15-30 psi is too much to work with or are you just stating that there is an easier method without the need for
pressure. I'm considering this approach as a SS vessel for this could be used for a number of other applications where up to 20 atm (300 psi)
shouldn't be a problem, so the reactor could serve a few purposes.
I was talking to somone else interested in this who does a lot of work with electrolisys, induction heating and ozone generation (he's a tesla coil
and HV enthusiast). Some homebuilt O3 generators can put out a large amount, putting the residential commercial units to shame - and they aren't too
difficult to build with modern electronics - biggest issue may be a HV sparkgap on some units. I've been interested in trying some O3 experiments and
was wondering if passing it over a bed of sulfur would instantly make SO3 and if so would this be explosive, create flame or what?
As far as the SO2 generation, I;m not sure the best method for this ATM but am trying a few different methods. I''ve tried burning straight sulfur
and even after it has melted and formed a black top layer, it doesn't seem to keep burning. I've never really worked with sulfur before so I'm doing
my reading on that now.
As note, I'm using agricultural "flours of sulfuf" which is a super fine dust/powder. I know people say that it isn't always that pure but I
dissolved some in hot toluene, filtered at 1um, evaped and only lost about .1% total weight. If it was CaCO3 as the additive (as many say it is) then
I would have suspected it have filtered out - unless it dissolves in toluene..?
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Melgar
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It sounds like what you need is an oxygen concentrator, which I would recommend you build with the assistance of someone who knows what they're doing.
Building an oxygen concentrator will teach you all about how gases behave differently based on applied pressure, how pressure regulators work and why
they're so important, and basically all the stuff you need to know in order to properly design and build anything more dangerous than that. So, if
you want to be able to build it yourself, I recommend using the "pressure swing adsorption" design, explained in detail here:
http://www.oxygentimes.com/learn/how-oxygen-concentrators-wo...
The oxygen concentrator will allow you to perform the contact process at lower pressures, and will also allow your sulfur burner to stop going out so
quickly. It's really hard to keep a sulfur flame going at the right intensity to generate the proper amount of SO2 with 20% oxygen in the atmosphere,
but should be pretty trivial at a higher concentration. The only thing that's even slightly hard to source can be found here:
http://www.ozonesolutions.com/products/Replacement-Parts/Mol...
Now, you may also want to study adiabatic heating and cooling; aka the reason that the film "The Day After Tomorrow" failed so badly at properly
warning the public of the dangers of climate change. In industry, they will compress and decompress gases specifically to heat and cool them. They
also have all sorts of fancy compressors that they use to raise pressures on their reactors so that they take up less space and react more quickly.
This is probably not your top concern at the moment, since you probably want to perform a successful reaction before optimizing it, so I'd probably
recommend working on boosting the oxygen for both burning sulfur and oxidizing SO2, and also set it up so that it's something you can control and
measure pressure in.
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violet sin
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If you look at the last page of that thread Magpie linked, you will see some of my posts from shortly after I joined. Though I did a ton of reading,
think I still clearly came off,... Hmm,. Lets just say "wishful thinking" ( not always fun to see early ideas immortalized online). Very ambitious
ideas for an amateur, pretty dangerous to-boot. For a number of reasons, never got around to making sulfuric acid or SO3. Mainly
budget/time related. But I'm glad I had more time to think before making the devil's stainless tea kettle.
Angry, Hot, and pressurized H2SO4/SO3 doesn't sound so much like fun these days. Splashing one's self with cool
<20'c drain cleaner was an eye opener. Watching hot drain cleaner blow through filter paper without stopping, just a charred black outline of the
droplet's shape on its way to the beaker, a reminder.
I just think it is dangerous enough, an open ended system should be used, perfect yield be damned. It's not the easiest trick to pull, why try to
optimize it immediately. Simple at first would be better. Bisulfite decom -> SO2, addmix dried air or Oxygen in quartz tube with
catalyst, scrub resultant gas through sulfuric acid for SO3 then through separate NaOH for the SO2. Suckback protection
required! Even that is an overly simplified, potential nightmare in practice.
It was pointed out to me, that this is more of a method of making sulfur trioxide/olium, than just sulfuric acid. That SO3 is scrubbed
into Hot sulfuric acid because its too reactive towards water. The (basically)over-proof sulfuric is slowly diluted down to an acceptable level. The
number of things to go wrong is astounding. Even a minor issue like SO2 leak could be lame. Alpha explosion much more severe.
The issues aren't insurmountable, but they require much planning. This subject revisits my attention every now and again. That darn challenge keeps
calling. the materials and safety just aren't sorted out to my satisfaction yet. Like no place to try it safely, live in town. You may have access
to better materials, equipment, funding, location and knowledge than I had. And your story may have a lower pH ending than mine has so far  play safe though.
------
after-thought edit: I am in the process of learning about arduino micro-controllers currently. parts already on order but yet to arrive( nano &
uno ), so reading it is. it occurred to me that data logging might be incredibly helpful for situations like this; where keeping an eye on several
temp probes and flow meters would be problematic, especially if you don't want to hover over boiling hatred.
for a few bucks it would be nice to at least see a temp probe on the catalytic chamber ( in what ever form). tweeks like different SO2
sources, sulfur burners or S-candles even could be monitored.
I'm sure a cheap cobbled together data logger system would be useful in other settings as well. I mean if the the thing was made for something
serious like the above, you could no doubt break it out of hiding for mundane reactions as well. for an arduino nano, an Uno, 2x nano
extension/sensor shield, breadboard power supply was $10.75, now that is cheap.
[Edited on 13-1-2017 by violet sin]
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