| Pages:
1
2
3
..
7 |
madscientist
National Hazard
Posts: 962
Registered: 19-5-2002
Location: American Midwest
Member Is Offline
Mood: pyrophoric
|
|
Electrochemical ozone generation
I wasn't sure just where this thread would belong, but since the reaction that produces the final product isn't electrochemical, I thought I'd put it
here.
This method of preparing ozone that I just thought of relies on the following reaction:
3H2O + 3F2 ----> 6HF + O3
This method would involve electrolyzing a solution of HF with a copper cathode, and a graphite anode. The cell would be divided into two sections so
that they have seperate atmospheres; the side with the anode would be air-tight, with a teflon tube to lead away fluorine, ozone, and oxygen gas; the
side with the cathode would just be open, to allow hydrogen gas to escape. The gasses produced at the anode would be bubbled through water, and the
resulting gas (hopefully mostly ozone) stored.
Obviously the hydrogen fluoride is regenerated, so this process would cost as much as the electricity.
I weep at the sight of flaming acetic anhydride.
|
|
|
rikkitikkitavi
Hazard to Others
Posts: 192
Registered: 17-6-2002
Member Is Offline
Mood: No Mood
|
|
If you electrolyze a aqeous solution of HF, O2 will of course be formed at the anode instead of F2.
The eletrochemical for the reaction
2H2O=>4 H+ + O2 + 4 e- is 1,23 V
2F- => F2 + 2 e- : 2,83 V.
/rickard
|
|
|
Polverone
Now celebrating 21 years of madness
Posts: 3186
Registered: 19-5-2002
Location: The Sunny Pacific Northwest
Member Is Offline
Mood: Waiting for spring
|
|
Why this method?
Even if it does work, this sounds like a pretty complicated setup. If you're going to build a complex device, why not build a device for silent
high-voltage discharge? That's how most ozone generators work, I believe. You might want to inquire about this at PowerLabs. They do a lot of high
voltage electronics stuff.
|
|
|
madscientist
National Hazard
Posts: 962
Registered: 19-5-2002
Location: American Midwest
Member Is Offline
Mood: pyrophoric
|
|
I hear that ozone generators that work by electric discharge in oxygen give poor yields and concentrations of ozone.
I weep at the sight of flaming acetic anhydride.
|
|
|
rikkitikkitavi
Hazard to Others
Posts: 192
Registered: 17-6-2002
Member Is Offline
Mood: No Mood
|
|
yeild can be up to 15 %, based upon energy consumed,if prechilled,cleaned oxygen is used. yield is normally around 5-10%
The reaction F2+H2O => HF + O3 + O2 doesnt show high yield either. Plus that the reaction between F2 and H2O is extremely violent (like most compounds
reacting with F2)
/rickard
|
|
|
IodineForLunch
Harmless
Posts: 34
Registered: 28-8-2002
Location: NJ
Member Is Offline
Mood: bored
|
|
Madscientist's first reaction given will work without electricity if hot water is used.
However, I don't know of many amateurs that have the want or the way to make fluorine...
David Hansen
|
|
|
Marvin
National Hazard
Posts: 995
Registered: 13-10-2002
Member Is Offline
Mood: No Mood
|
|
I'm a fan of weird reactions, particulaly ones that dont follow obviosly from the chemistry.
You can make ozone by electrolysis of dilute sulphuric acid. The best conditions are, Pt/Ir electrodes, sulphuric acid between 1.075 to 1.100
density, the solution of the anode must be very cold, -14C is suggested and the current density must be as large as possible so long as it doesnt
cause too much heating, so a small thin electrode is better. With a Pt electrode 0.1mm by 11mm embedded in glass (so the surface 0.1mm by 11mm long
is the only surface exposed to the solution) the oxygen that comes off contains up to 28% of ozone.
In hindsight you can see why, oxygen radicals form at the anode to give oxygen and ozone molecules and the higher the concentration, the more ozone.
Ozone is extremely nasty, allthough I know most of you know that, not everyone reading this thread will.
|
|
|
S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline
Mood: Enhanced
|
|
An article on the H2SO4 process that I stumbled upon:
Attachment: iec_44_2207_1952.pdf (651kB)
This file has been downloaded 1635 times
|
|
|
S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline
Mood: Enhanced
|
|
Might as well also upload these JACS articles while I'm here. One talks of the other so here are both 51, 2676 (1929) and 47, 1844 (1925). These are
also articles that I stumbled upon (not looking for lab ozonizers in the literature) earlier, so maybe there is something better out there that has
been published but no one has uploaded here. Your turn.
EDIT: BTW, these JACS articles are off-topic and probably best posted in some other existing thread as these are a standard sort of ozonizer, unlike
the IEC device above. But no one is going to make it anyways so oh well IMHO.
[Edited on 30-1-2006 by S.C. Wack]
Attachment: O3.zip (563kB)
This file has been downloaded 1180 times
|
|
|
stygian
Hazard to Others
Posts: 242
Registered: 19-9-2004
Member Is Offline
Mood: No Mood
|
|
http://freepatentsonline.com/4316782.html
|
|
|
12AX7
Post Harlot
Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline
Mood: informative
|
|
| Quote: | Originally posted by madscientist
I hear that ozone generators that work by electric discharge in oxygen give poor yields and concentrations of ozone. |
So? Bubble it through some liquid nitrogen. Filter out the ozone crystals.
 !
Tim
|
|
|
Marvin
National Hazard
Posts: 995
Registered: 13-10-2002
Member Is Offline
Mood: No Mood
|
|
Hmm, just because its solid doesn't mean it won't dissolve. Sure it won't?
Theres also the little problem of the crystals tending to detonate when they warm up. Solid and liquid ozone is a bit... unpredictable.
|
|
|
12AX7
Post Harlot
Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline
Mood: informative
|
|
Well, eventually either by adding enough O3 or evaporating enough N2, it'll precipitate, you're right it might dissolve to a pretty good amount in the
mean time though.
Explosiveness is just semantics. Hence the 
Tim
|
|
|
Fleaker
International Hazard
Posts: 1252
Registered: 19-6-2005
Member Is Offline
Mood: nucleophilic
|
|
If kept at LN2 temperatures, the black/purple crystals of ozone can be filtered from the LN2. Even cold like that, the fumes are really aggressive and
it sublimates rapidly. IIRC, it is soluble to a degree in liquid oxygen not so much nitrogen? If I remember where I placed the literature and my lab
book I'll post it up.
Ozone is a rather fleeting substance, even in a strongly basic solution (say pH of 14) it doesn't last too long as the dissolved gas. Rather apt to
forming hydrogen peroxide too :-P.
|
|
|
Flip
Hazard to Others
Posts: 116
Registered: 7-12-2005
Member Is Offline
Mood: No Mood
|
|
O3 by electric discharge
| Quote: | | I hear that ozone generators that work by electric discharge in oxygen give poor yields and concentrations of ozone. |
This is far from the truth. I built an ozone generator three or four years ago that was capable of turning methanol blue at -40 deg C by complexing
with the solution. I used a 75 kV neon sign transformer, copper wire, and a borosilicate glass tube as my dielectric. Also, I managed to give myself
ozone poisoning with is *not* fun. Let's see, what else could it do? Oh yeah, the thing dissolved rubber and all manner of surgical tubing making my
bubbler a huge challenge to construct. Of course, I have an O2 tank and regulator. If you try electric discharge through ordinary air, the O3 yeild
will not be high, but will still be enough to smell from several feet away (ppm range).
If you're interested in building one I have a design that works exceptionally well and puts out a great yeild of ozone. My only concern was that the
output would be TOO big.
|
|
|
garage chemist
chemical wizard
Posts: 1803
Registered: 16-8-2004
Location: Germany
Member Is Offline
Mood: No Mood
|
|
I'd be interested.
I have tried to build an ozone generator myself, by taking glass tube (7mm outer diameter) and inserting a wire, and coating the outside with
Aluminium foil.
It worked extremely well with a flyback, and not so well with a neon transformer.
With the flyback, hissing blue discharges were formed and the tube became hot quickly, this rapidly diminished ozone yield since high temperature is
very detrimental to ozone.
I overcame this by bending the glass tube in a W shape and immersing it in salt solution which served as the outer electrode.
This worked best. However, the glass tube broke because the setup was too fragile.
The output of the thing, directed at a piece of paper soaked with KI solution turned it DEEP BLACK instantly. No starch was added to the KI.
I'd like to hear about your setup!
[Edited on 6-3-2006 by garage chemist]
|
|
|
Flip
Hazard to Others
Posts: 116
Registered: 7-12-2005
Member Is Offline
Mood: No Mood
|
|
I'll see if I can describe it without illustrating any pictures...
The basic idea is a borosilicate tube with thin gauge copper wire threaded tightly around the outside, and a heavy gauge wire suspended through the
center.
The output can be modified by adjusting how "threaded" the outside of the tube is, or how much spacing is between each coil. My coil had spacing of
about 1 cm/coil. The coil is taped down at both ends with electric tape, but you'll have to make certain that the ends of the tube are far enough
away from the wire to prevent arching from the inside of the tube to the outside on the ends.
The most important part of this setup are the end-pieces, and my setup used a PVC pipe fitting with a threaded cap at each end. You'll have to bore
a small hole in the outside of the fitting on one side, in order to thread some of the outside wire through the hole so you can attach the alligator
clip from the generator. Now, the reason the threaded caps are important, you'll need to make sealed end pieces... I accomplished this by cutting
round pieces of plexiglass to fit on the inside of the end caps. You'll take your heavy gauge copper wire and heat it up so you can stick it through
the plexiglass. This way, the wire will be suspended in the center of the tube from end to end, and the system will be sealed.
So in order to fit with the PVC fitting, you'll need a much wider diameter tube. I used one of those long lightbulbs for my prototype, but they are
too easy to break to be worthwhile, the borosilicate tube should, however, be of similar diameter. It's better to err by getting a tube too small,
because you can always wrap the tube with electric tape until it seals perfectly with the PVC fitting. You can order the borosilicate tube from any
glass-blower's supply catalog, they use the tubes to blow into other shapes.
When it's finished and turned on, it looks rather like a purple lightsaber with two handles. 
So you then need to bore two more holes into the plexiglass end pieces, and get double sided hose fittings (plastic) to stick through them so you can
attach hoses for input and output.
You can get an O2 tank and regulator for about 150$ total from Holox or a similar company. You can get the transformer from a neon sign company.
When you wire the transformer, make sure you use a cord with a ground, or you could get yourself in big trouble. Then all you need is some alligator
clips to run from your transformer to the exposed parts of each wire (taking care that there isn't any arching around the sides) and you're good to
go.
The output of this design is incredible, and my main concern was that it would be so strong that it would tear benzene rings as well as double bonds,
but it didn't seem to effect the aromatics. You can calibrate the output with a known molar amount of an alkene in a DCM/methanol solution in
acetone/dry ice. When the alkene is completely cleaved (1-1 molar ratio here) the O3-methanol complex will begin to form and the solution will turn a
light shade of royal blue... it's kind of self-indicating. Once you know the moles O3/min, you can utilize it as a precise instrument of organic
synthesis.
Just don't try to use neoprene hosing like I did, because O3 will corrode right through it, effectively melting it, and O3 will be released in huge
volumes into your workspace, giving you ozone poisoning, making your breating unbearably painful, and confining you to your bed for days. (I didn't
realize at first that the hose was neoprene).
All the same though, you should be able to complete the construction of it for about 250 USD. If you need any more specifics you can PM me, i'd also
be happy to draw a picture or two if I'm not really clearly expressing my design.
|
|
|
Flip
Hazard to Others
Posts: 116
Registered: 7-12-2005
Member Is Offline
Mood: No Mood
|
|
Forgive the crappy illustration, but here's a picture that should give you a rough idea of what i'm talking about. If anyone here is serious about
building one, though, it is fairly simple and I can walk you through the construction.
(picture attached)
|
|
|
S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline
Mood: Enhanced
|
|
[low yielding]
Microscale Production of Ozone
http://jchemed.chem.wisc.edu/Journal/Issues/2005/OctACS/ACSS...
http://jchemed.chem.wisc.edu/Journal/Issues/2005/OctACS/ACSS...
|
|
|
Natures Natrium
Hazard to Others
Posts: 163
Registered: 22-12-2004
Member Is Offline
Mood: No Mood
|
|
Hmm, I have a quick (and relatively uninformed) question. I was wondering how feasable it would be to use a length of copper tubing instead of a rod
for the center, so as to pass cold water through it continously and increase ozone yields. If one could skip the tank/regulator and just use CaCl2
dried air that would reduce the overall cost quite a bit (although Flip's design is still about US$500-5000 cheaper than the commercial designs I have
seen). Hmm, I wonder how it would affect my aquarium pump, which is a sealed design? I thought about running water through a condenser, with rod
inside and coil outside, but my gut instinct (without any real knowledge to back it up) says the water would interfer heavily with the corona
discharge. Maybe use cold salt water through the condenser and forgo the coil altogether? I guess I am just brainstorming here on alternate design
routes.
Oh yea, Flip, is that 75kV mentioned a typo for 7.5kV, or did you really use 75000V for your design? Oh, and did you attempt to use braided PVC
tubing, and if so how well did it stand up to the O3?
Does anyone else have anything to report on this interesting project?
-NN
\"The man who does not read good books has no advantage over the man who cannot read them.\" - Mark Twain (1835-1910)
|
|
|
roamingnome
Hazard to Others
Posts: 363
Registered: 9-9-2006
Member Is Offline
Mood: No Mood
|
|
Flip Said: I built an ozone generator three or four years ago that was capable of turning methanol blue at -40 deg C by complexing with the solution.
Im a bit behind as im putting the finishing touches on my first ozone generator now ..only 5 kV but with pure oxy im sure ill get something... so what
else was in the methanol ... huh.... i hope to be turning methanol blue soon
as well...
maninly cuase i want to open a bakey that sells almond muffin cakes... ya know the regular reasons
|
|
|
roamingnome
Hazard to Others
Posts: 363
Registered: 9-9-2006
Member Is Offline
Mood: No Mood
|
|
As far as reporting in general,, im basically copying a design from a web page
a parralell plate setup 2mil thick glass, The gap is spaced by microscope slides 1 mil thick.
im hoping that some clear silcone to seal the apparatus between random thicker glass will hold up for a while
the thing that i dont know is how the discharge region or path length affects production. who cares right
|
|
|
12AX7
Post Harlot
Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline
Mood: informative
|
|
A mil thick? I didn't know you could get glass in that size; that's like film!
Of course you know how the discharge will effect production. It needs to be a glow discharge, but not spark. Corona between two closely spaced
plates, supplied AC of any frequency or DC, is the ideal method.
Tim
[Edited on 11-19-2006 by 12AX7]
|
|
|
Natures Natrium
Hazard to Others
Posts: 163
Registered: 22-12-2004
Member Is Offline
Mood: No Mood
|
|
I just finished scouring the boards of anything with "Ozone" in the thread, and as an aside I found quite a few reactions that I was not aware were
capable with O3. Even more reason to make this work. :-)
Anyways, the thread I think I learned the most from is this one: https://sciencemadness.org/talk/viewthread.php?tid=1774&...
If I am understanding this correctly, the best method for Ozone production while still using a NST would be to NOT have a glass layer between the
electrodes? So the goal would be to get them as close together as possible without inducing an arc.
This flyback circuit looks interesting, and if I understand Martin correctly, a higher frequency output is very beneficial to producing ozone with a
glass insulator. I just have to wonder, how beneficial?
I would like to be producing at least 5g O3/hr with my setup. I may have to opt for the pure, dry oxygen source after all.
Also, MODS, maybe this thread should be moved to technical? I didnt mean to dredge up an old thread, but even O3 derived from the electrolysis of
sulfuric acid solutions seems more like a tech thread than a chem thread to me. *shrugs*
-NN
\"The man who does not read good books has no advantage over the man who cannot read them.\" - Mark Twain (1835-1910)
|
|
|
Natures Natrium
Hazard to Others
Posts: 163
Registered: 22-12-2004
Member Is Offline
Mood: No Mood
|
|
Though I know it to be folly to expect replies when posting upon on internet forum, still I pine for encouragement.
I was looking through my collection of resources (read:piles of crap), when I realized I have two objects in my possession that might be used for this
project.
1. .002" (.05mm) thick 99%+ copper foil
2. a 30cm long, 2.5cmID pure alumina catalyst tube
The first was bought for making a home made capcitor, I think. The second was purchased for attempting to produce PCl3 from a phosphate/carbon mix in
the presence of pure diatomic chlorine at 650C. However, I was never able to figure out a design which I felt would comfortably contain the stream of
650C Cl2, PCl3, and PCl5 exiting the tube. It was to be heated with NiCr wire and a 600w cieling fan dimmer, but I digress.
I am thinking that the alumina tube would make an excellent dielectric for this project, using tight fitting PVC caps (covered in PTFE) sealed with
rubber tape.
My questions are: would it (probably) be more effective to use a thin wrap of wire around the outside or the copper foil covering the entire outside,
and two, is the 2mm thick walls of the alumina tube plus the 1.25cm gap to the center rod going to be enough to prevent actual arcing (10.5kV, 30mA)?
Of course, the one MAJOR disadvantage to this design is that I wont get to see the cool purple corona. 
Any help, either fact or speculation, would be appreciated, as this is actually my first high voltage project. As always, I am most interested in the
information which will let me draw my own deductions, i.e. how to calculate how far apart two metal objects must be to prevent arcing at a specific
voltage.
Many thanks,
-NN
\"The man who does not read good books has no advantage over the man who cannot read them.\" - Mark Twain (1835-1910)
|
|
|
| Pages:
1
2
3
..
7 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
