blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Recovery of Pd from Pd/C catalyst
I'm in the strange position of having the option of buying 12 kg (yes, twelve kilogram!) of palladium on carbon (Pd/C) catalyst with a stated loading
of 0.5 w% Pd.
There are some problems with the material:
* it's old: sales receipt goes back to 1967
* it's quite coarse and lumpy with lumps up to 5 mm size
And 0.5 % loading is of course very low.
I believe catalytic activity after all that time will be very low and that the only value of this material lies in the Pd it contains.
But at such low levels extracting the Pd from its carbon carrier may pose challenges too.
If anyone here has experience with or sound ideas about this kind of recovery, I'd be grateful for their comments.
[Edited on 3-10-2014 by blogfast25]
|
|
|
forgottenpassword
Hazard to Others
Posts: 374
Registered: 12-12-2013
Member Is Offline
Mood: No Mood
|
|
http://www.technology.matthey.com/article/57/4/289-296/
|
|
|
Pok
potassium Prometheus
Posts: 176
Registered: 5-12-2010
Member Is Offline
|
|
Make a BBQ and separate the Pd from the carbonates and oxides of less noble metals in the ash. Maybe with NaBH4 as stated above. This would save a lot
of chemicals for leaching.
[Edited on 3-10-2014 by Pok]
|
|
|
plante1999
International Hazard
Posts: 1936
Registered: 27-12-2010
Member Is Offline
Mood: Mad as a hatter
|
|
Well, depending on the price of the material, it could be highly lucrative to extract it considering the efforts needed.
First you have two choice for the carbon, either you use oxygen to burn it off, or an oxidizer like potassium nitrate.
Then you take your product, dissolve in water, and filter to get the insoluble. This will increase the content of palladium enormously.
Lastly, you proceed like any regular palladium reclaims, there is tutorial on the net (and youtube).
[Edited on 3-10-2014 by plante1999]
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Thanks all, so far.
@FGP: interesting looking paper.
@pok: incineration did occur to me to but I'm afraid some of the Pd will literally go up in smoke, which also not environmentally great.
@diddy: Pd spot price is about $760/oz, not exactly nothing.
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by plante1999  | First you have two choice for the carbon, either you use oxygen to burn it off, or an oxidizer like potassium nitrate.
[Edited on 3-10-2014 by plante1999] |
That's a lot of nitrate! With potential loss of Pd as entrainment too...
|
|
|
plante1999
International Hazard
Posts: 1936
Registered: 27-12-2010
Member Is Offline
Mood: Mad as a hatter
|
|
Well, even if it cost 20$ or 40$ in nitrate, it would be worth it considering the value of the product. One could take an enamelled cooking pot and
melt the nitrate in it with the cover. Then one could slowly add the catalyst on a certain length of time to diminish entrainment lost.
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
For the immediate future (i.e. this weekend) I need to assay the Pd content first. After that it will be easier to decide whether to buy the lot or
part of it or not. One possibility would be to sell it to a processor with the capacity to handle that quantity better than I could. Potentially less
profitable, of course...
|
|
|
forgottenpassword
Hazard to Others
Posts: 374
Registered: 12-12-2013
Member Is Offline
Mood: No Mood
|
|
There's a graph on the Johnson Matthey paper that shows concentration leached per hour. It has gone up to over 20% leached at room temperature by the
third hour. There's no reason why you couldn't handle 12 kg with a HDPE jerry can or two, and a little patience.
[Edited on 3-10-2014 by forgottenpassword]
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
I was just looking at the documentation that came with the three 100 g samples and they're a real bit of 'petite histoire' from 1967! More importantly
they all state "0.5 % Pd on granular carbon (4/8 mesh) (American method)". This would imply the Pd is really just on the surface of the carbon
'chips', eliminating the need to crush it all up.
| Quote: Originally posted by forgottenpassword | | There's a graph on the Johnson Matthey paper that shows concentration leached per hour. It has gone up to over 20% leached at room temperature by the
third hour. There's no reason why you couldn't handle 12 kg with a HDPE jerry can or two, and a little patience. |
I really like that paper but borohydride as a reduction agent sounds like serious overkill.
[Edited on 3-10-2014 by blogfast25]
|
|
|
forgottenpassword
Hazard to Others
Posts: 374
Registered: 12-12-2013
Member Is Offline
Mood: No Mood
|
|
There's no need to use borohydride. This paper uses a similar leaching solution followed by formic acid to recover the palladium
http://www.sciencedirect.com/science/article/pii/S0926860X05...
I don't know much palladium chemistry, but maybe it is possible to get PdCl2 out of solution without much trouble. As far as I am concerned it is a
more useful and saleable product than Pd metal or Pd/C. Making Pd/C from PdCl2 is straight forward too.
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Pd (II) is very easy to reduce to Pd (0) (it's a 'noble' metal after all!). Hence my remark about 'overkill'.
I was thinking formaldehyde or sodium metabisulphite in near neutral conditions. Both cheap as chips...
[Edited on 3-10-2014 by blogfast25]
|
|
|
S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline
Mood: Enhanced
|
|
It's supposed to precipitate a more active form.
Testing the material and the market before messing with it would hardly be unwise.
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Not sure what you mean here. If I go ahead the recovered metal will be sold as Pd metal powder, mainly because I don't have a smelter.
[Edited on 3-10-2014 by blogfast25]
|
|
|
S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline
Mood: Enhanced
|
|
Why not assume that as-is active (if you can prove it to yourself) perhaps name brand Pd/C (regardless of loading) should be worth rather more than J.
Blow's alleged Pd, even without consideration of the expense of fussing out the Pd.
Cinnamaldehyde comes to mind but surely there are better tests.
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by S.C. Wack | Why not assume that as-is active (if you can prove it to yourself) perhaps name brand Pd/C (regardless of loading) should be worth rather more than J.
Blow's alleged Pd, even without consideration of the expense of fussing out the Pd.
Cinnamaldehyde comes to mind but surely there are better tests. |
I'm not well equipped to test activity, although I could probably stretch to trying hydrogenation of hex-1-ene with ammonium formiate and check for
unsaturation with bromine water. Not sure how representative that would be though. I don't like the physical form (mesh 4/8) and the low loading much.
A cinnamaldehyde based test? Got any references?
[Edited on 4-10-2014 by blogfast25]
|
|
|
S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline
Mood: Enhanced
|
|
Cinnamaldehyde came up as a particularly available alkene, and a substrate well-known to give different products with Pd/C under different conditions.
It seems safe to say that if one's Pd/C can go to not just hydrocinnamaldehyde but somewhat beyond, it's fine, but analysis of a possible 3 component
mixture obviously has problems.
The phenol on eugenol is a bonus though, with convenient acid/base isolation.
I haven't looked up how much a Johnson Matthey et al. Pd/C costs new or on ebay, so the assumption is that 12 kg is worth a bit of analysis.
PS: another test worth doing would be exacting Pd recovery (or not) from the ash in the BBQ.
[Edited on 4-10-2014 by S.C. Wack]
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
I think it’s worth assessing activity but I’ve no cinnamaldehyde. I can get cinnamic acid easily.
Two extraction tests were run more or less in parallel, both on 100 g of the material.
In one I used 150 ml of 10 % HCl, 5 % H2O2, 3 hours at about 100 C, with high speed magnetic stirring (as per that paper FPW linked to).
In the other one I used 50 ml of HCl 37 %, 11 ml of HNO3 70 % and 62 ml of water. This is roughly 15 % HCl with a good dollop of nitric acid added.
This was high speed magnetic stirred at about 100 C but only for about 1 hour. NO/NO2 generation was very bearable.
After 3 h the first one was hot Buchnered and the filtrate neutralised with a calculated amount of NaOH 20 %. Still hot, 50 ml of 35 w% formaldehyde
(methanal) was added but no precipitation of Pd metal was observed. But another 25 ml of HCl 70 % and 5 g of zinc powder caused the precious little
palladium to drop out. End of assay tomorrow.
The second run was stopped after 1 h of simmering, the 100 ml of water was added and the beaker cooled to RT, then cold Buchnered. To the filtrate was
added 55 ml of 33 w% NH3. This caused some presumed Pd(OH)2.nH2O to precipitate. Faint wisps of palladium (II) hydroxide:
Tomorrow I’ll turn the Pd(OH)2 into PdCl2.2H2O, a useful general precursor to Pd and compounds.
[Edited on 4-10-2014 by blogfast25]
|
|
|
Dan Vizine
National Hazard
Posts: 628
Registered: 4-4-2014
Location: Tonawanda, New York
Member Is Offline
Mood: High Resistance
|
|
Old catalysts that are thought to have become inactivated are easily "reactivated" by simply treating the catalyst with hydrogen. Just do a
hydrogenation with no substrate present. It will be as active as it ever was. It's probably unnecessary if the container was well closed, though.
I've recovered precious metals from spent catalysts on many occasions by simply leaching with aqua regia, evaporating the clarified acid to dryness,
re-dissolving in water and treating with hydrazine sulfate. All-in-all, a pretty much sledgehammer-inspired route that you don't really need. Because
of the potential redox reaction between the oxidant and the reductant, C, I never did more than maybe 20 - 30 grams of 5 - 10 wt % Pd/C at once.
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Dan:
How do you reactivate 12 kg (twelve kilogram) of 50 year old Pd/C in a laboratory-cum-cottage-industry business though?
The physical form (4/9 mesh) strikes me as something for industrial use, not really my market.
Ta.
|
|
|
Dan Vizine
National Hazard
Posts: 628
Registered: 4-4-2014
Location: Tonawanda, New York
Member Is Offline
Mood: High Resistance
|
|
Hi blogfast,
Good point, although, if the best purpose planned for it is to simply use it as a catalyst, I'd just reactivate it as needed. And I wouldn't even do
that until I saw that I needed to.
The mesh size is unusual. But due to the way that the Pd is deposited (everywhere), crushing it would be easy enough and give acceptable material.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
