axehandle
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Pt on inert substrate catalyst.
I'm going to make some. It's an interesting and expensive experiment that will look good on camera, just my cup of tea.... heh.
But I'm a bit at a loss regarding what substrate to use --- any foolproof ideas?
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vulture
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Carbon is generally used, Al2O3 might be possible too depending on the application.
Carbon has the advantage that you can form a very homogenous Pt/C catalyst by pyrolysing a Pt salt with a organic substance.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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bobo451
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SiC also makes a good Pt substrate if you can use a CVD method for coating. SiC is non-porous though, so if you need the surface area it will not
work as well.
SiC holds heat well, so has the advantage of countering flucuations in your feed temperature if the bed temperature is critical to the reaction.
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axehandle
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Think "Oswald Process"  Or another catalyzed gas oxidation process,
like SO2 + 1/2 O2 --> SO3
The goal is to make a "generic" Pt catalyst that will work in many different processes.
[Edited on 2004-7-24 by axehandle]
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unionised
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Platinised asbestos used to be the common choice; it seems to be out of favour these days. You could try Pt on glass- or quartz- wool.
[Edited on 25-7-2004 by unionised]
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axehandle
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AC electrolysis with Pt electrodes in HCl(aq)
I'm doing it right now, to see if it really will dissolve.
The electrodes (two Pt wires) are submerged 15mm into the 30% HCl, placed 15mm apart.
The power supply is a 9V AC adapter I found in one of my junk boxes.
It's bubbling. Very much. Shudder. This is a ridiculously expensive experiment.
Edit: It's smelly. Am I making ClO<SUB>2</SUB> here, incidentally?
Edit2: Shit. I seem to have fried the power supply. In retrospect, I probably should have used a resistor in series. Let's see if I can repair
it...
Edit3: No. The magic smoke had escaped. Really not my day today. Have to convert a DC adapter to AC... let's see... don't have any.
Contemplating using wall AC... Sigh -- this entire day has been one big fucking waste of time. I hate Sundays.
[Edited on 2004-8-23 by axehandle]
[Edited on 2004-8-23 by axehandle]
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BromicAcid
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How about running some wires straight from the socket to the solution?  I did it
once, before I knew better, to try and plate copper on something, the solution was boiling within a minute. I doubt you are producing ClO2 though.
[Edited on 8/23/2004 by BromicAcid]
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axehandle
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Well.... with the slight modification of putting a 40W bulb in series with the wall AC, it could work just fine. I'll see if I can do a little
hack on a table lamp I've got somewhere...
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axehandle
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The Fantastic Christmas Light Resistor
I knew I would one day find a use for this ugly xmas lighting thing!
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axehandle
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The resistance was too large -- no bubbling. I've replaced it with a 40W bulb; now it's bubbling again. The Pt wires look like they're
dissolving: the submerged parts look definitely polished. We'll see how long this takes, if it seems to be incredibly slow I'll crimp the
electrodes flat in the submerged end. But I shouldn't be hasty here, it would be a waste of platinum.
Edit: Does anyone have a scientific reference to this method of AC:ing Pt electrodes in HCl? I'm especially curious as to the speed of the
reaction, it seems slooooow...
[Edited on 2004-8-24 by axehandle]
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axehandle
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There, the electrodes seem consumed. Scary story actually: The 40W bulb I used as resistor seemed to have died, so I streched out my hand to move the
reaction vessel.... Little did I think of the strange stain on the top of the vessel making it look like it had "boiled over". WHAM! 230
nice volts right through my hand. One of these days my luck will run out... 
Nevertheless, I'm pretty sure I know have about 1g of H<SUB>2</SUB>PtCl<SUB>6</SUB> in HCl. That's a start.
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garage chemist
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Old thread I know, but I have recently made some platinum on asbestos which turned out to be an extremely active catalyst.
If held into a stream of hydrogen, it instantly begins to glow and then ignites the hydrogen. Platinum wire only does this when it is preheated, while
the Pt- asbestos does this even when at room temperature.
The great thing about this is that only an extremely small amount of platinum is needed! The standard concentration of platinum on asbestos is 1%.
I dissolved 0,005g (5mg, a 3,3mm piece of 0,3mm diameter wire) of platinum in 2ml aqua regia (this takes over 6 hours, and it must be held at 80-
90°C the whole time by means of a water bath. Hammer the wire flat to increase the surface, otherwise it's going to take very long).
Aqua regia can be improvised by adding KNO3 to HCl when HNO3 isn't available.
This solution was diluted to 20ml with water, 0,5g fluffy asbestos were suspended in it and then 0,5g ascorbic acid in 10ml water were added, stirred
well and left over night.
At the next morning, a small amount of hydrazine sulfate was added , stirred and slowly heated to 50°C to complete the precipitation. The asbestos
should look grey now.
It is filtered, washed with water and dried.
Before use, it must be heated directly over the bunsen burner (it should glow red hot) for a few seconds to activate it.
It is going to be used in a proof-of-concept catalyst tube for the oxidation of SO2 to SO3 (for Oleum production- I have all the conc. H2SO4 I need,
but Oleum is not available). If it works, more platinized asbestos will be made for a bigger catalyst tube.
Asbestos is difficult to get, I have only a small amount.
An alternative inert carrier is quartz wool, but that's enormously expensive (more than 50€ per 50g). Glass wool can't be used (it melts too
easily).
I heard that ceramic (alumina) fiber does also work, but I am unable to locate a source.
What other materials (preferably in fiber form, or similarly porous) can be used as a carrier for finely divided platinum?
Can anyone give a method to make platinum-charcoal, with activated charcoal as carrier?
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S.C. Wack
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http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/1962/84/i14/...
Perhaps a rockwool for hydroponics or fireplaces could work for SO3. Probably not.
Here in the US, Pt wool is OTC as catalytic heater heads but rather expensive, at least $30.
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garage chemist
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OK, tried the platinized asbestos for conversion of SO2 to SO3, and what happened? Nothing. Not the smallest trace of SO3. No idea why it isn't
working. I heated it real hot (until the burner flame got yellow due to sodium in the glass), and tried lower temps, too.
With a spiural of Pt wire instead, I got some SO3, but the amount is incredibly small. It just smokes a little bit out of the exhaust, thats all. SO2
stench is still overpowering at the outlet.
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unionised
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You might want to try Pt on silica gel. Less nasty than asbestos and commercially available so I guess it works.
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Magpie
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Today I picked up a used Zebco catalytic heater for $1 at a yard sale. It had an unused 1lb cylinder of propane so I figured I really couldn't lose.
I didn't know how these heaters were constructed or operated. The following website seems to cover the subject:
http://www.catalyticheaters.us/catalyst.htm
Now I'm wondering if I can put this heater to use for syntheses requiring a Pt fixed bed catalytic gas phase reaction.
Any thoughts or suggestions?
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AJKOER
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Ceria and Thoria are known inexpensive (but not quite as an efficient) substitute catalyst for Pt. Doing a comparison experiment would be interesting
to me.
Also, for those without any spare Platinum laying around, note that Ceria (CeO2) is available from pottery supply shops.
Why still pricey as a rare earth metal ($45 a pound), it is still far cheaper than Pt.
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S.C. Wack
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Quote: Originally posted by Magpie  | | Now I'm wondering if I can put this heater to use for syntheses requiring a Pt fixed bed catalytic gas phase reaction. |
I ripped out the wool from a Coleman Sportcat when they came out, and tried using it that way, with ethanol and methanol, too sloppily. The tiny
amount there is reactive like you'd expect...until it's poisoned...I've been meaning to explore combinations with hydrogen...if I had a tank of
hydrogen on hand and could have connected it to the head, that would have been nifty. So much to do...a non-lazy person should get on that.
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The WiZard is In
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Prepare a small quantity of platinized asbestos as follows:
Exp. 105.—Prepare a small quantity of platinized asbestos as follows:
http://tinyurl.com/3r95kex
platinized asbestos, obtained by
http://tinyurl.com/3rgqetr
[Edited on 31-5-2011 by The WiZard is In]
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Morgan
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You can buy replacement hand-warmer wicks that are made of some sort of platinized mineral fiber. Once I put some methanol in my handwarmer and then
attached the platinized wick unit which just snaps on over the cotton filled tank. Funny it got so hot I couldn't hold the hand-warmer and it didn't
need any preheating unlike when using the recommended fuel.
Here is someone's example of one.
http://www.youtube.com/watch?v=m3noYOVTBzk
This is me squirting some methanol on a platinized wick removed from it's element. There is a spring that sleeves inside the tube-shaped woven wick
that holds the shape and I took that out too. So it's just a wick at room temperature that quickly heats up when misted with methanol. I found if you
tease/fray the ends of the wick it helps the ignition. The fibers are most likely hazardous to your health, so avoid breathing them if you toy with
these wicks, whatever they are made of.
http://www.youtube.com/watch?v=UtkEfzpZ4Sg&NR=1
http://preparedness.com/jonhanwarrep.html
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Bert
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Rather than start a new thread, here is a patent of interest to those contemplating (or electroplating!) Ostwald process catalysts...
Catalyst for production of nitric acid by oxidation of ammonia
US 5336656 A
http://www.google.com/patents/US5336656
Example #4 caught my eye... No noble metals. A catalyst and substrate that a sophisticated amateur might make at reasonable cost. LOW PRESSURE
OPERATION WITH HIGH EFFICIENCY.
Now about finding a cheap source of ammonia gas?
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EXAMPLE 4 A foam structure 8 inches in diameter and 0.8 inches thick and containing 30 pores per inch was produced by immersing a polyurethane
expanded foam into a ceramic slurry of cordierite (magnesia alumina silicate) powder, After firing to temperatures in excess of 1300° C. the ceramic
foam was dipped into an aqueous colloidal dispersion of alumina containing about 20% by weight of Al2 O3. The sample was dried and calcined to 500°
C. for one hour, The foam was found to have picked up 8% by weight alumina. The alumina coated foam was dipped onto a solution of 12% zinc as zinc neo
decanoate in toluene. The weight pick up measured after calcination to 500° C. was 5%. This zinc oxide and alumina coated foam was then dipped into a
12% cobalt as cobalt neo decanoate in toluene and dried and calcined at 500° C. The weight pick up was 15% as cobalt oxide. This catalyst was placed
in the ammonia oxidation reactor and ignited with the electric spark ignitor. The reactor was run for two weeks before evaluation, Analysis of the
ammonia input to the reactor showed 10% ammonia in air, The output was measured at between 9.1 and 9.4% NO giving a corrected conversion of 92 to 95%.
Pilot Plant Trial Experience (comparison with Pt gauze) The reactor chamber of the pilot unit utilizes 16, 8 inch diameter gauzes. The flow rate is
600 scfm which gives a linear velocity of 1.355 meters per second and an approximate pressure drop of 1.9 inches of water. The feed is approximately
6.7% ammonia in air. The reactor operates at 4 psig and atmospheric pressure is about 13 psig. A platinum catalyst on foam was prepared with 10.5% Pt
on an 8 inch diameter 0.80 inches thick, 30 pores per linear inch alumina foam. This catalyst loading had a platinum loading of 1.38 troy ounces in
the reactor. (The metal contained in the gauzes pack was 9.94 troy ounces.) At this metal loading the metallized ceramic catalyst is electrically
conductive with a resistance of about 0.4 ohms per inch. This metallized foam was placed on a non metallized alumina support segment and mounted in
the reactor. The gauze reactor was operated at 760°-800° C. The performance of the catalyst was checked by taking samples of the reacted gases and
titrating for nitric acid and ammonia. Twelve samples were taken over a six hour run. The results showed that the gauze converted 95% of the ammonia
to nitric acid and furthermore in the absorption system used approximately 45-46% acid was produced. The metallized foam converted up to 96% of the
ammonia to nitric acid and for unexplained reasons gave a stronger acid strength of about 50%. After these tests were completed only the acid strength
was used to monitor the performance and nitric acid was produced for an additional 60 days. At the end of the 60 days, the catalyst was performing
acceptably, with no evidence of reduced activity and the run was stopped only to recover the catalyst for analysis. Assay showed that there was no
metal loss (assay in 10.50% assay out 10.54%) and there was no loss of performance was detected. TABLE
2______________________________________Comparisons of Foams to Gauze Thickness of Foamto Match Gauze(Surface Area of 80 mesh gauze is 1.53 Square
meters of wire persquare meter gauze) Pressure Drop at 1.355 m/sec, (inPores Per Linear Inch Thickness of Foam H2
O)______________________________________10 0.229 cm 0.7220 0.114 cm 1.3830 0.076 cm 1.9050 0.046 cm 6.11______________________________________ From
about 12 to 15% Pt by weight the metallized structure has a continuous and electrically conductive film. The ceramic surface is substantially coated.
Table 3 below shows the platinum reduction achievable by using the coated form. This made possible because the ceramic makes up the core and the
platinum is on the surface where it is effective as a catalyst. TABLE 3______________________________________Comparisons of Pt loadings on Gauze and
MetallizedCeramic Foams(Coated at 12% by weight)(80 mesh wire gauze has 1.78 troy ounce per square footof gauze)Pores per linear inch TO/Sq
Ft______________________________________10 0.114520 0.057230 0.038250 0.0229______________________________________ It is estimated that the catalysts
and process according to the present invention, if substituted for the conventional platinum gauze can reduce the metal content of the catalyst charge
over 90%.
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Dan Vizine
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Pt catalyst is usually most active on a carbon substrate and, most commonly, it is sold and used in this form.
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Texium
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Thread Moved
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