Sciencemadness Discussion Board

Pt on inert substrate catalyst.

axehandle - 24-7-2004 at 12:17

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?

vulture - 24-7-2004 at 12:53

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.

bobo451 - 24-7-2004 at 14:04

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.

axehandle - 24-7-2004 at 14:16

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]

unionised - 25-7-2004 at 14:27

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]

AC electrolysis with Pt electrodes in HCl(aq)

axehandle - 22-8-2004 at 17:03

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]

BromicAcid - 22-8-2004 at 17:28

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]

axehandle - 22-8-2004 at 17:32

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...

The Fantastic Christmas Light Resistor

axehandle - 22-8-2004 at 17:48

I knew I would one day find a use for this ugly xmas lighting thing!


axehandle - 23-8-2004 at 07:35

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]

axehandle - 31-8-2004 at 08:02

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.

garage chemist - 11-6-2006 at 14:28

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?

S.C. Wack - 11-6-2006 at 20:16

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.

garage chemist - 12-6-2006 at 07:00

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.

unionised - 14-6-2006 at 11:44

You might want to try Pt on silica gel. Less nasty than asbestos and commercially available so I guess it works.

Magpie - 6-5-2011 at 18:20

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?

AJKOER - 29-5-2011 at 13:41

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.

S.C. Wack - 29-5-2011 at 16:42

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.

Prepare a small quantity of platinized asbestos as follows:

The WiZard is In - 30-5-2011 at 16:58

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]

Morgan - 1-6-2011 at 14:05

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

Bert - 20-8-2014 at 08:12

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?

Quote:

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%.

Dan Vizine - 9-10-2014 at 18:03

Pt catalyst is usually most active on a carbon substrate and, most commonly, it is sold and used in this form.