Preparation of Palladium on Charcoal

[TheBlindGenius]

I was reading on rhodium's site, the writeup that follows

Palladium on Carbon (30% Pd/C)
Prepare a solution of 8.25 g of palladium chloride (or an equimolar amount of palladium chloride dihydrate, PdCl2*2H2O) in 5 ml of concentrated hydrochloric acid and dilute with 50 ml distilled water. Cool the solution in an ice-salt bath and add 50 ml of 40% formaldehyde solution and 11 g of acid-washed activated charcoal*. Stir the mixture mechanically and add a solution of 50 g of potassium hydroxide in 50 ml water, keeping the temperature below 5°C. When the addition is complete, raise the the temperature to 60°C for 15 minutes. Wash the catalyst thoroughly by decantation with water as above and finally with dilute acetic acid, collect on a buchner filter and wash with water free from chlorine or alkali. Dry at 100°C and store in a desiccator.

https://www.thevespiary.org/rhodium/Rhodium/chemistry/pd-catalyst.faq.html

My main question is, why is it that for the other two Pd/C preparations described on the page, which are for 5% Pd/C, the use of a hydrogenator is needed, but not for it seems not for this one?  I do not have a hydrogenator, they are quite expensive.  SWIM does have a shaker and a pressure vessel though, and could get a hydrogen tank.  Could this be used somehow?  Swim has both stainless steel and glass pressure vessels.  Would the stainless steel one work for the other two syntheses, or would the palladium fuck with the metal, as in the Wacker?  Or would the other chemicals "neutralize" that effect? Pd/C is quite hard to get around these parts.  Hydrogenation.....damn, they always talk about hydrogenation reaction in classes but never describe the apparatus or how it works or anything.  And I'm already in 3-level Chemistry classes!

[terbium]

My main question is, why is it that for the other two Pd/C preparations described on the page, which are for 5% Pd/C, the use of a hydrogenator is needed, but not for it seems not for this one?  ...
And I'm already in 3-level Chemistry classes!
I don't know what 3-level chemistry classes are but I presume that this means college level classes. So you are taking college level classes and have to ask this question? This really should be asked in the Newbee Forum. Hint, what is the purpose of the formaldehyde in this preparation.

[TheBlindGenius]

In college it goes 1 and 2 level usually for freshmen, sophomores, 3 and 4 level for seniors.  And I said I'm in them, not that I do well in them      I know formaldehyde is HCHO, but I still do not understand what occurs.  You've got an acidic aqueous solution of PdCl2, then you add HCHO and charcoal acid-washed activated charcoal, then KOH.  Could you please explain?  If it has to be moved to newbee, so be it.

[terbium]

The formaldehyde gets oxidized and the palladium ion gets reduced.

[Sunlight]

CTH reduction doenst' work well with any of my homemeade Pd/C, may be the problem is the charcoal...

[TheBlindGenius]

When you say doesn't work well do you mean it doesn't work or you need to use much more?  If it does work, how much should one use of this 30% homemade with formaldehyde stuff as compared to store bought 10%?

[TheBlindGenius]

link for catalyst preparation.

http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv3p0685

Notice method B also uses alkaline formaldehyde as the reducing agent.
The article states
"The catalysts A, B, and D are prepared and stored until required with the palladium in the reduced form ready for use."

But then says
"Catalysts reduced with formaldehyde carry no adsorbed hydrogen and are less pyrophoric."

I assume it is good that they are less pyrophoric (less danger of fire) but I would think you want adsorbed hydrogen?  I don't know.

Also, the article specifies what type of charcoal to use.
First it says "nitric acid-washed Darco G-60"
then states in the footnotes "Norit, Darco, or other carbons may be used. The carbon is heated on a steam bath with 10% nitric acid for 2–3 hours, washed free of acid with water, and dried at 100–110° before use"

They and other articles I've read on Pd/C prep seem to stress "acid-washed" charcoal.

[RoundBottom]

also, the literature does not mention what mesh of charcoal is best.  i have seen in in fine powder form, (messy as all get out, and unlikely to filter well) to small bits (like fine bread crumb powder), up to small and large chunks like you'd find in your fireplace.

what is the best size for these procedures and what size does it come in from a commercial producer?

[foxy2]

what is the best size for these procedures and what size does it come in from a commercial producer?

Your looking at the wrong parameter.  Size of the granule doesn't matter.  The key parameter is the microscopic pore properties which are highly variable based on what the carbon originates from and under what conditions its prepared. 

If you want a measurement thats most important I would say that Surface Area would bee the one.

[TheBlindGenius]

Is Formalin OK? Formalin is 37% formaldehyde, but I think it has like 10% MeOH to prevent the formaldehyde turning into para-formaldehyde.

[Sunlight]

Check the Rhodium's threat about CTH reduction of cinammic acid. I've had the same problems with that Pd metal catalyst than with Pd/C catalyst, I suspect the origin may be in impurities in the photographic PdCl2 I've always used.

[Rhodium]

Threat?  

[Sunlight]

Someday I should study english seriously. Sorry.

[ClearLight]

< Having search Rhod's site and utsfe I'm left w/ the question >

In Wizard's write up he mentions using pd on Barium Sulfate, commonly used to avoid catalytic poisoning.  In the Zip on the Adam's catalyst it mentions that attempting to reduce the halide salt (Cl) will result in failure w/ Pd/C due to catalytic poisoning. 

  While wizard did mention using Pd/C as a sidenote to Pd/BaS04, the question i have is,

 " When attempting a reduction using Pd/C is it necessary to have your precursor in the Sulfate form for this to go?"

  "Will chloride form cause the catalyst to poison and the reduction fail?"
 
 "If the reduction goes w/ X.Cl does the Cl reduce the life of the Pd/C catalyst"?

  Thx!

[SPISSHAK]

you would buffer with sodium acetate to prevent this poisoning?

[ClearLight]

Some of these reactions are done in GAA so sodium acetate is not added in these recipe's.. I'm trying to understand whether hcl deactivates the catalyst, or the GAA buffers the process...

[badbody]

In Chem lab, I've seen very small explosions, (flash of light and whisps of smoke), after addition of 10% Pd/C, that were blamed entirely on the overly fine mesh of the Carbon.  If memory serves correct, the reaction still proceded as expected.

[ClearLight]

with an extreme death wish add the catalyst to the reaction vessel as a powder, and not pre-mixed with the solvent and poured in...

Of course, not flushing the reaction vessel completely w/ H2 prior to adding powder, and dropping it in from 12-20 cm's falling through the air will immensely faciltate angel wings...

[Lilienthal]

With an extreme death wish also use methanol as a solvent for catalytic hydrogenations...

[Barium]

The only solvent which should be avoided is 1,4-dioxane, and that is only if raney-type of catalysts are used. At high temperatures dioxane and raney-catalystes can react in a very researcher un-friendly way. There is only in a very few instances when water must be excluded from the reactor. Therefore catalsyts wetted with their own weight of water should always be used.

This is how catalysts should be added to a reactor:

Add the catalyst first. When any dust has settled add 50% of the solvent to be used. Add the substrate/reagents followed by the remaining portion of solvent.

If the solvent catches fire when added to the catalyst just place something flat over the mouth of the reactor. This effectively kills the fire. If there is a fire in the reactor there will just be some flames and no explosion. But this is a very good reason not to keep anything flamable near the reactor.