Acuyo
Harmless
Posts: 29
Registered: 29-6-2016
Member Is Offline
Mood: activated
|
|
High pressure Wacker O2 generator/RV
I've been kicking around the idea of a sorta-high Pressure PVC wacker vessel (ala SRV), but with an O2 feed connected instead of using an attached
tank - 40-50psi sustained for a few hours at a time is what I'm thinking of. For the O2, I was thinking of using another PVC cylinder with H2O2 and
Mg2O (I think that's right for Magnesium Dioxide, it's from the older 6v batteries).
The completed reactor vessel would: be assembled properly with fine threads and blue glue; would have a pressure gauge and a relief valve and probably
not run over 40psi -- far below the capability of PVC although I should probably put the holes in the caps and not the sides of the cylinder (I
believe this would be stronger but I'm no physicist), and make sure all fittings are well re-enforced. Also I plan to use high-pressure vinyl tubing
between the two cylinders, fit onto hpde barb fittings and scew-anchored under hose clamps.
My questions are: Is H2O2 and MgO a relatively safe way to generate O2? Is there any hydrogen or any potential for dangerous peroxides or gasses (I
think its 'Browns Gas' that's a specific mix of H and O)? Also, I'm sure %30 peroxide is a better way to do this, would the lower percentages at most
pharmacys be ok here, or should I just hunt down the %30?
I suppose some garage experiments are in order, but mostly I want to know about the potential for dangerous gasses or peroxides and I probably have a
couple weeks before I could do much more than assemble this. Thanks, any suggestions or comments appreciated.
edit: Also, if someone could post the reaction mechanism, I'd be obliged.
[Edited on 8-7-2016 by Acuyo]
|
|
|
Metacelsus
International Hazard
Posts: 2531
Registered: 26-12-2012
Location: Boston, MA
Member Is Offline
Mood: Double, double, toil and trouble
|
|
Batteries have manganese, not magnesium, dioxide. The formula is MnO2. (Also, the formula for magnesium dioxide is MgO.)
Pressurized cylinders of oxygen and fuel (basically anything organic) are a great way to lose an arm if you're not careful. I would advise against
doing this.
|
|
|
Acuyo
Harmless
Posts: 29
Registered: 29-6-2016
Member Is Offline
Mood: activated
|
|
Quote: Originally posted by Metacelsus  | Batteries have manganese, not magnesium, dioxide. The formula is MnO2. (Also, the formula for magnesium dioxide is MgO.)
Pressurized cylinders of oxygen and fuel (basically anything organic) are a great way to lose an arm if you're not careful. I would advise against
doing this. |
Thanks for the correction re: Mg vs. Mn.
Yes, appreciate the warning also. I understand the risks, I think 40-50 psi in PVC and while wearing protective gear when testing and running the
device would be mandatory. My understanding is that PVC is good for somewhere around 200 psi, if not more (I'll look this up)? I've worked with
aquatic systems so I have some experience with PVC (and a few high-power tater guns, heh). I imagine any holes drilled could potentially compromise
the structure enough to dramatically reduce the ability to hold pressure, but still, 40-50 psi doesn't seem to me like I'm asking too much? It's not
really *that* much pressure it seems? I'm truly wide open for opinions or suggestions here.
I'm going to do some more searching on MnO2, if anyone has more feedback on this reaction with H2O2, again I'm
interested in anything you have.
My completely uneducated guess for this reaction is: MnO2 + H2O2 -->> 3O2 + Mn + H2O
Thanks again for anything you have.
edit: Maximum reccomended operating pressure for 4" ID Sch. 40 PVC is 133psi according to: http://www.engineeringtoolbox.com/pvc-cpvc-pipes-pressures-d...
If I'm careful about how many holes I put in the rig, and where I put them, I think the PVC should be fine at low temps and pressures. I plan to drop
in a 1l beaker or maybe even a mason jar inside the rxn (not O2generator) vessel, so as to hopefully remove much chance of corrosion or
contamination. Also, if I see Sch. 80, I'll use that, as it looks like it's good for another 60psi with the 4" piping.
[Edited on 8-7-2016 by Acuyo]
|
|
|
Texium
Administrator
Posts: 4508
Registered: 11-1-2014
Location: Salt Lake City
Member Is Offline
Mood: PhD candidate!
|
|
Yeah, that is very incorrect. What really happens is MnO<sub>2</sub> catalyzes the decomposition
of hydrogen peroxide into oxygen gas and water. No manganese metal is formed in the process.
But this is good news for you, because the manganese dioxide is totally reusable. You just keep adding more peroxide and it will keep generating more
oxygen with water as the only byproduct.
|
|
|
DJF90
International Hazard
Posts: 2266
Registered: 15-12-2007
Location: At the bench
Member Is Offline
Mood: No Mood
|
|
Why does the oxygen need to be pressurised? Wacker oxidations will usually run at atmospheric pressure under oxygen. The manganese dioxide is a
catalyst in the decomposition of hydrogen peroxide, and as such is unchanged during the reaction:
2H2O2 -MnO2-> O2 + 2H2O
|
|
|
Acuyo
Harmless
Posts: 29
Registered: 29-6-2016
Member Is Offline
Mood: activated
|
|
| Quote: Originally posted by DJF90 | Why does the oxygen need to be pressurised? Wacker oxidations will usually run at atmospheric pressure under oxygen. The manganese dioxide is a
catalyst in the decomposition of hydrogen peroxide, and as such is unchanged during the reaction:
2H2O2 -MnO2-> O2 + 2H2O
|
Well, my understanding is that the rxn consumes quite a bit of oxygen, and so that a) pressure, b) very strong stirring, c) a PdCl2
catalyst, and d) a CuCl2 co-catalyst all work together to supply enough oxygen to get the yields hopefully up to ~%80 or better.
Maybe if I just ran it so that the pressure wasn't very high but the oxygen supply was consistent, the results would be similar to the high-pressure
results? Hrm..
@ZTS16 - Awesome, this makes sense, thanks.
[Edited on 8-7-2016 by Acuyo]
|
|
|
CuReUS
National Hazard
Posts: 928
Registered: 9-9-2014
Member Is Offline
Mood: No Mood
|
|
Instead of generating O2 using chemicals, why not get an ozone generator and then decompose the ozone to get O2 ?
2 O3=3 O2
[Edited on 9-7-2016 by CuReUS]
|
|
|
Sulaiman
International Hazard
Posts: 3558
Registered: 8-2-2015
Location: 3rd rock from the sun
Member Is Offline
|
|
easier (but £200) is a medical oxygen concentrator
mine : http://www.ebay.co.uk/itm/OXYGEN-CONCENTRATOR-STEADY-FLOW-FO...
2litres/minute 90% oxygen.
Useful for chemistry, oxy/gas torch etc.
|
|
|
Acuyo
Harmless
Posts: 29
Registered: 29-6-2016
Member Is Offline
Mood: activated
|
|
I'm seeing Manganese Dioxide abbreviated as both MnO and MnO2 on the web - which is it? I want to be able to calculate exactly how much O2 this
reaction will put out so I can estimate what I'll need, and also maybe what the rxn is consuming.
So if it doesn't consume any manganese to generate O2, using a very small amount should help to regulate the O2 liberated? On youtube it looks as
though the reaction is very vigorous, being able to mediate it a bit I think will be important for this purpose.
Good ideas re: ozone or just an OTC electronic generator, I'll keep these in mind.
[Edited on 9-7-2016 by Acuyo]
|
|
|
Sulaiman
International Hazard
Posts: 3558
Registered: 8-2-2015
Location: 3rd rock from the sun
Member Is Offline
|
|
a few thoughts;
35% H2O2 needs to be treated with great respect,
it can bleach thumb skin (instead of a stopper when shaking) in seconds
many things can catalyse an uncontrolable decomposition
I can't imagine safely controling oxygen production rate by adding the MnO2 in a measured ammount ... how do you stop ?
Here in EU concentrated H2O2 is no longer available to the public.
Try 3% to 12% OTC H2O2 added from a pressure-equalising drip funnel
(I learned my lesson - tried chlorine generator with normal drip funnel ... immediately spent £9.99 on a p-e 24/29 funnel)
scaled up for your application.
safer, cheaper, more controllable
The third paet of this video gives an idea. http://www.sciencemadness.org/talk/viewthread.php?tid=67121
[Edited on 9-7-2016 by Sulaiman]
|
|
|
Acuyo
Harmless
Posts: 29
Registered: 29-6-2016
Member Is Offline
Mood: activated
|
|
At this point, I really don't see a need for %30+ H2O2 here.
Warnings duly noted - thanks.
|
|
|
zed
International Hazard
Posts: 2277
Registered: 6-9-2008
Location: Great State of Jefferson, City of Portland
Member Is Offline
Mood: Semi-repentant Sith Lord
|
|
Ummm. The earliest personal verbal report I got on the O2-Wacker, involved an explosion.
Keeping in mind that O2 + any hydrocarbon..... may equal detonation, I would stick with a well known procedure, and I would carefully research
reaction vessels.
|
|
|
Acuyo
Harmless
Posts: 29
Registered: 29-6-2016
Member Is Offline
Mood: activated
|
|
Sulaimman: two ways I can think of to regulate pressure (aside from an actual pressure regulator, which I also plan to implement - I think some
redundancy here is smart) are by adjusting the the tightness of the PVC threads on either the generator, or the reaction vessel itself slightly so
that the vessel starts to bleed off after a point - this is obviously a pretty big hack but it would work to bleed off pressure quickly.. I think a
better idea though would be to built in a simple check valve (very easy) with PVC, basically a spring-valve built into the top that gives once a
certain amount of pressure accumulates.
| Quote: Originally posted by zed | Ummm. The earliest personal verbal report I got on the O2-Wacker, involved an explosion.
Keeping in mind that O2 + any hydrocarbon..... may equal detonation, I would stick with a well known procedure, and I would carefully research
reaction vessels. |
Ok this is exactly why I'm posting and asking questions about this. Do you know if these were the explosions reported while using the alkyl nitrite
variations, or with just plain pressurized 02? I've read some cases of the former (possibly related to nitrosamines produced during the rxn, the
explosions seemed to happen post-rxn, during distillation), but I don't recall any explosions un-related to completely inappropriate pressure vessels.
Thanks if you're able to elaborate on these accounts at all.
[Edited on 17-7-2016 by Acuyo]
|
|
|
hissingnoise
International Hazard
Posts: 3940
Registered: 26-12-2002
Member Is Offline
Mood: Pulverulescent!
|
|
| Quote: | | Instead of generating O2 using chemicals, why not get an ozone generator and then decompose the ozone to get O2? |
Seriously, an ozone generator for oxygen-supply is a laughable idea ...
|
|
|
MrHomeScientist
International Hazard
Posts: 1806
Registered: 24-10-2010
Location: Flerovium
Member Is Offline
Mood: No Mood
|
|
To clear up the compound confusion:
- Magnesium and manganese are not the same thing! You probably know that, but you'd be surprised how often I get comments to that effect.
- There are many oxides of manganese: see https://en.wikipedia.org/wiki/Manganese_oxide
- Manganese dioxide (MnO<sub>2</sub>; the di- tells you there are two oxygens) is part of the black powder inside lantern batteries. There
is also a lot of graphite mixed in, so it's far from pure.
- Manganese dioxide catalytically decomposes hydrogen peroxide to form oxygen, and remains unchanged and reusable.
|
|
|
zed
International Hazard
Posts: 2277
Registered: 6-9-2008
Location: Great State of Jefferson, City of Portland
Member Is Offline
Mood: Semi-repentant Sith Lord
|
|
As I recall, the explosion took place using O2 under pressure.
I have no details. The explosion was a passing topic, in a conversation, with a middleman. I did not speak directly with the chemist.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
