fusion of cats substrates with sodium peroxide

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Arthur,

I have a book with some info at the house. I'll post it later when I get home.

Steve
 
Arthur,

The proper ratio is 10 parts sodium peroxide to 1 part cat.

Here's what I've got:

  1. Cat honeycomb is crushed to -200 mesh
  2. Material dried for 2 hours at 500C
  3. Throughly mix dried, crushed cat material with sodium peroxide, 10 parts to 1 part honeycomb material (eg 0.25 cat to 2.5 g sodium peroxide).
  4. Place in a zirconium crucible and fuse @ 550C-650C for 1-2 hours.
  5. Allow to cool.
  6. Place crucible in a beaker twice it's size.
  7. Carefully add distilled water (100mL in example above) to the crucible/beaker to dissolve the fusion material. This will sputter as the water is added.
  8. When all reaction ceases carefully add conc. HCl = 1/2 the volume of water used. (50mL in example). Reaction may sputter.
  9. When all reaction ceases add conc. HNO3 = the amount of HCl used.
  10. When reaction finishes bubbling transfer to a large beaker.
  11. Throughly rinse the zirconium crucible and it's beaker repeatedly with distilled water. Combined these rinses with the reaction solution in the large beaker.

The above reaction is taken from Mark Payette's Thesis on Catalytic Converters. I also referenced several other websites for the temperature data on peroxide fusions as Mark left this data out of his thesis. If anyone has access to the document "Talanta 30,1,21-39; 1983" I'm sure more information can be uncovered.

I have also contacted an analytical lab in hopes that they will provide me with more information on the process.

I have more literature on the reaction if you are interested.

Steve
 
This process is limited by the use of a zirconium crucible.

I know where to get them, and they are not cheap. I'm willing to help you out on getting one Steve, if you do not have one.


I will look for that reference when I get a chance.
 
I have a small one (about 100mL internal volume), it's more of a melting dish than a crucible. It has one high side and one low side.

I got it second hand and its was contaminated with an unknown crust when I inherited it.

I'm interested in a new one Lou, also if you know how to clean this one up that would be really great. I've considered a dremel and a grinding bit, but I didn't want to bugger up the insides if I don't have to.

Steve
 
Zirconium is not easily etched by acids, only HF, H2SO4, and HClO4 really faze it. I would suggest you try dilute HCl (HCl can attack Zr too, but very slowly unless hot or with H2O2).

I very rarely use Zr crucibles, mostly Pt, Ni, or Coors ceramics or those alumina ones like I sent you once before. If something sticks, a good solution for the metal ones is to heat it to a good red heat and toss it in water. The adherent layer should come off.

I'm really shooting in the dark; it would be nice to see a picture of your crucible. You could also try getting some slivers off the material off and see what (if anything0 it dissolves in so you know how to attack it.


Lou
 
Platdigger said:
I have nearly 2000 zirconium crucibles, but, ha, they are no bigger than a good sized thimble.........
Randy
Click to expand...

I'd like to see a picture of one of them if that's possible, Randy. Perhaps taken with a coin in the same picture for a perspective on size.

Harold
 
thanks steve for the information----it is not viable to me because na2o2 is 580dollars a kilo here --as a cat has + or minus 1kilo the ratio 1 to 10 is unthinkable as a start----
 
Arthur,

I agree, sodium peroxide fusion should be left as an analysis technique, not a recovery technique.

I'm working on setting up a heated system which circulates HCl and periodically injects small amounts of clorox into the bottom of the container.

My preliminary testing with mildly hot hcl and clorox shows good extracting ability. I have also found quite a bit of literature backing up the technique.

A second even more enticing method to me is the dual tube furnace method I mentioned in previous post. It has nearly quantitative yields, its fast, and does not require the substrate to be dissolved. Although more expensive to setup the equipment would rapidly pay for itself if you turn out enough cats.

Steve
 
What is the dual tube furnace Steve? I searched through some of your recent posts but didn't find any mention of it.
 
Skippy,

It's an arrangement of two tube furnaces in series that extract the Pt/Pd in the first furnace at 550C, and the Rh is extracted in the second furnace at 1000C.

The crushed feedstock material is feed into the first furnace opposite the direction of gas (50/50 mix of Cl2/SO2) flow. The product of the reactions is condensed upon existing the furnaces. The first furnace produces volatilized Pt/Pd chlorides which condense between 200-300C. The second stage produces RhCl3 which condenses at 750-850C.

These exit products are collected with condensation tubes inserted into the kilns.

This method is documented by E-Tek.

Steve
 
I am working on a similar process, but not using SO2. It too is nigh on quantitative. At the moment, I'm perfecting the process; flow rates, continuous feed, values recovery, temperature gradient. I am using alumina that I have ''spiked' with Pt, Pd, and Rh (so I know the loading).

Steve, I should mention that there are very nice clamshell tube furnaces available that have 3 or 5 heating zones. That is what I am using :) If/when you buy a tube furnace and the reaction gear(it's insanely expensive!) I'll be glad to point you in the right direction.

There are many, many gas mixtures that can be used, even chlorinated hydrocarbons, or COCl2 (not nice!) even.

If I do a write up on it, it will be in the next two months, but only after I determine that the process is nothing which should be kept secret.

Lou

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Lou,

The article is loaded with data and third party analysis of the feedstock and tailings from the reactions.

The reason for the mixed gases was to reduce the Aluminum that is volatilized from the substrate. The two tube arrangement is to provide separation of the products (Pd/Pt chlorides) from the RhCl3. They found that Cl2 alone tends to attack the Alumina forming aluminum chloride which contaminates the Pt/Pd chlorides.

I also have other design variations in mind, but it's all on paper for now as you pointed out the equipment for this stuff isn't cheap. I too was considering a multi-zoned furnace as well as several other modifications to the method.

The results from the E-Tek experiments showed >98% extraction of all PGMs.

Steve
 
Exactly right Steve, you'll have the alumina form AlCl3 which will also distill over, which when you add to water makes a nasty mess and a lot of HCl. It isn't a majority product in the least Steve, in fact, the equilibrium lies to the left and the ''alumina'' staying intact.


I'd like a copy of the paper/patent Steve. Nice to read what others are doing with the gas phase transport.



Lou
 
Thanks Lazersteve, it's an interesting technique, read it a couple times before. Implementing this sort of mixed gas continuous process is probably way beyond my resources, though.

Hope to hear more about your chlorox technique. For all the pessimism surrounding the aqueous chlorine processes, I figured someone would iron out the details and get it working.
 
Amazing Lou! I wonder how you get time to visit here, go to work and develop your apparatus! When you say you are not using SO2 gas, are you using a reducing gas at all? Not trying to pry away your secrets, but I'm curious.
 
Yes, I'm also using a reducing gas, there's not too many of them that won't also reduce the PGMs :) I'll give you a hint, its a mono oxide of a non metal :)
 
Lou said:
Yes, I'm also using a reducing gas, there's not too many of them that won't also reduce the PGMs :) I'll give you a hint, its a mono oxide of a non metal :)
Click to expand...

Oooooo... cryptic! :wink:
 

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