TheBlindGenius (Hive Bee)
02-14-03 19:29
No 407815
      Preparation of Palladium on Charcoal  Bookmark   

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 5C. When the addition is complete, raise the the temperature to 60C 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 100C and store in a desiccator.


../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!

The working man is a sucker
 
 
 
 
    terbium
(Old P2P Cook)
02-15-03 04:14
No 407997
      Palladium on carbon  Bookmark   

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.


All those moments will be lost in time, like tears in rain.
 
 
 
 
    TheBlindGenius
(Hive Bee)
02-15-03 06:37
No 408035
      Yes, terb...  Bookmark   

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 blush wink 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.

The working man is a sucker
 
 
 
 
    terbium
(Old P2P Cook)
02-15-03 08:03
No 408068
      Redox.  Bookmark   

The formaldehyde gets oxidized and the palladium ion gets reduced.

All those moments will be lost in time, like tears in rain.
 
 
 
 
    Sunlight
(Pioneer Researcher)
02-15-03 15:04
No 408119
      CTH and homemade Pd/C  Bookmark   

CTH reduction doenst' work well with any of my homemeade Pd/C, may be the problem is the charcoal...
 
 
 
 
    TheBlindGenius
(Hive Bee)
02-15-03 21:30
No 408229
      Sunlight....  Bookmark   

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%?

The working man is a sucker
 
 
 
 
    TheBlindGenius
(Hive Bee)
02-20-03 02:07
No 409940
      Here is a.....  Bookmark   

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 23 hours, washed free of acid with water, and dried at 100110 before use"

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

The working man is a sucker
 
 
 
 
    RoundBottom
(Hive Addict)
02-20-03 09:16
No 410041
      grainularity of charcoal  Bookmark   

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?

Now with 12% more Bottom!
Nymphomania is not a disease, its a goal! (Methadist)
 
 
 
 
    foxy2
(Distinctive Doe)
02-20-03 09:56
No 410054
      what is the best size for these procedures and  Bookmark   

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
(Hive Bee)
02-24-03 08:23
No 411387
      What kind of formaldehyde?  Bookmark   

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

The working man is a sucker
 
 
 
 
    Sunlight
(Pioneer Researcher)
02-27-03 01:17
No 412086
      Same fiasco with Pd metal  Bookmark   

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
(Chief Bee)
02-27-03 02:00
No 412101
      I'm harmless  Bookmark   

Threat? wink
 
 
 
 
    Sunlight
(Pioneer Researcher)
02-28-03 00:58
No 412402
      Thread  Bookmark   

Someday I should study english seriously. Sorry.
 
 
 
 
    ClearLight
(Hive Addict)
04-17-03 02:31
No 427427
      Question on Chloride poisoning of pd/c - Urgent!  Bookmark   

< 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!

Infinite Radiant Light - THKRA
 
 
 
 
    SPISSHAK
(Hive Addict)
04-17-03 05:58
No 427480
      Is'nt that why  Bookmark   

you would buffer with sodium acetate to prevent this poisoning?
 
 
 
 
    ClearLight
(Hive Addict)
04-18-03 04:39
No 427714
      Not in wizX's writeup  Bookmark   

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...

Infinite Radiant Light - THKRA
 
 
 
 
    badbody
(Hive Bee)
04-23-03 05:46
No 428836
      regarding mesh of charcoal  Bookmark   

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
(Hive Addict)
04-24-03 04:53
No 429074
      Only fools  Bookmark   

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...

Infinite Radiant Light - THKRA
 
 
 
 
    Lilienthal
(Moderator)
04-24-03 16:48
No 429140
      With an extreme death wish also use methanol...  Bookmark   

With an extreme death wish also use methanol as a solvent for catalytic hydrogenations...
 
 
 
 
    Barium
(Hive Addict)
04-25-03 11:51
No 429300
      Nah  Bookmark   

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.

Freaky
 
 
 
 
    Organikum
(Hive Addict)
04-27-03 18:47
No 429772
      Cl and Pd/C  Bookmark   


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



This I dont understand completely - Also it would be helpful if you would specify (link!) WizardXs writetup and the Adams catalyst .zip file. Damn you have searched - must we all do it again? [/quote]


"Will chloride form cause the catalyst to poison and the reduction fail?"



I have seen many references where a halide is reduced by catalytic hydrogenation, and for example the ROSENMUND is a name reaction doing exactly this. So I say: NO. No fail because of the Cl.

[/quote]"If the reduction goes w/ X.Cl does the Cl reduce the life of the Pd/C catalyst"?[quote] Usually not. The Cl should react with the provided H (or another available compound except the catalyst) to HCl (or else). In the case of HCl this wont be bad as acidic conditions support the hydrogenation. I would say that the availability of hydrogen is a main factor here (Barium tells this also again and again...). If you run short on available hydrogen the Cl might poison the catalyst - if H is available this wont happen. (this refers to the magic stirring/shaking/mixing in cat. hydrogenations - or more theoretical: masstransfer problematics).
Hydrogenation with noble metal catalysts is a reaction where it is near impossible to take out isolated factors as it is a complex interdependent system.
But baselines exist:
- Clean reagents. This says here your reagents may be dirty like shit as long as they contain no poisoning and no deactivating compounds. Catalyst poisons - the most hated - are: H2S and CO, deactivators No.1: organic sulphur compounds. Poison is end of prey, deactivators can be beaten sometimes by ultrasound and other tricks.
- Catalyst: The preparation guides on Rhodiums page give you a Pd/C catalyst of low to very low activity. (If somebody does not agree on this he may clear this with Mr. Rylander himself, who is the originator of this. He saw it as necessary to explizitely mention this in his book on hydrogenation methods.  On catalyst preparation he strongly advised not to prepare but to buy them. Period. )
Successful relieable reproducable homepreparation for high activity noble metal catalysts is not to find here nor elsewhere. (but soon will - I hope - and I wish you success Clearlight! The old chemists could make it, you will master it too!).
- Pressure: Maybee with industrial quality catalysts STP reactions are easy but not with homemade catalysts - for sure. 3 to 5 atm are to handle and are titulated as "low" or "elevated pressure" in chemistry. (high pressure is beyond 250atm....)The closed vessel makes also the control of the parameters much easier also the uptake of hydrogen can be simply monitored. Last but for sure not least: There is more hydrogen in the reaction mix and the masstransfer is not so problematic then. (you still have to shake the hell out of it or to apply a "stirrer" which has only the name common with what you usually imagine by hearing the word: "stirrer")
- Time: Oh yes the main part of the reaction is often done in 5 to 15 minutes. For superior results - to push yields in reductive alkylations from 80% to near 95%, 5% to 10% gain are usual, it makes sense to let the vessel charged with hydrogen sit for at least 12 hours with slightly reduced temperature and pressure (20%-30% less both) and medium shaking (in difference to the hard shaking at reaction start).

And finally a use for this URUSHIBARA Ni-catalyst! It can be used to clean solvents/reactands from catalyst poison. Boiling URUSHIBARA catalyst with the compounds before hydrogenation degasses (very important! CO!) and absorbes the bad ones (limited - its not possible to clean heavy contamination this way). Regarding the ease of preparation of Uru-Cat it might be worth the effort as degassing is necessary anyways (helpful at least).

Somebody with a good library access looking up how Rosenmund prepared his Pd/BaSO4 and Pd/C and the activated charcoal for Pd/C....  This would be a charm. (I cant do it - seriously, no lazyness)
Freifelder and Rylander already relied on industrial produced catalyst. The literature before WWII hints that there have been big differings in quality - selfmade or not. After what I know by now, it is rather probabel that for reproducable self-preparation of a relieable active catalyst it will be necessary to selfprepare the carrier (activated charcoal or else) too. Animal charcoal, special plant charcoal...   And NO! I am convinced that just using NORIT for example is NOT a wise decision. (In the longer run it should be possible to find one of the uncountable brands of act. charcoal useful for ones purposes - this wont be one of the very big ones I guess, as they make their products after other specifications than being perfect as catalyst carrier).

Hope that Barium, the big Hydrogenoser, agrees with most I told - I realy would prefer a common line now to popularize catalytic hydrogenations a little bit. Hdrogenations over noble metal wont ever get a mass movement but to stand so far out this technique has not deserved at all. (I promise to behave too. Yes. I will! laugh)

Solidarity of those who love it! Common fight against common nonsense! (like: hydrogen -> HINDENBURG; 3atm -> blockbusting explosions; Pd/C -> causing firestorms instantly and always when in contact with air; and more).



some points worth to mention quick I thought.
venceremos!
ORG smile


noble, noble, noble and some diamonds why not?
 
 
 
 
    ClearLight
(Hive Addict)
04-28-03 21:39
No 430035
      Answering my questions  Bookmark   

Thx Org for the references I've been reviewing them...

  I'm 3/4's of the way through my 2.5" of patents I printed out, however some PM's cleared up the questions:

   1.)precursor  HCL salts do not affect the Pd/C - Pd/BASO4 reactions

   2.) Catalytic activity is dependent upon the surface area of the Pd on the support.  Reduction of your catalyst in H2 is not recommended due to large (>25A) pd crystals being formed. Formaldhyde reduction is preferred.

   3.) Functional groups (aldehydes etc) on the carbon can wack the pd and cause large (reduced surface area) Pd crystals.

   4.) Pd/C in Wizard's write up is 1 shot. Not recommended

   5.) Pd/Barium Sulfate looks very good...experimental to follow.

   The catalytic support carbon is on order and will arrive shortly... Preparation of ones own Activated Carbon has so many variables and requires such extreme temp/pressure gradients that controlling these variables is more complex than most synthesis's here.  And you need a scanning electron microscope for pore size quality control. However I am going to try it anyway. There are several manuf. of Activated Carbon that have rather nice automated selection engines for your catalytic choices.


   Various patent preparations use condensation of the Pd from Sodium salts and use of H2O2 to control crystal formation size.  I will post a complete list of Useful patent refs after i've saved everyone the time by reviewing them.

   I have completed the theoretical analysis for a MW reduction via BASO4 + AcOH + Am.Form.  I'll run a microscale and report TLC results this week.

   To assist in Orgk's request, here are some cites that our eurobee's might be kind enough to look up ( and translate) to assist. I believe they have the original method(s)

Barium Sulfate Catalyst cites:

Houben, Die Methoden der organischen Chemie, 3rd ed., Vol. II, p. 500, Verlag Georg Thieme, Leipzig, 1930; Schmidt, Ber., 52, 409 (1919).

Mozingo, Harris, Wolf, Easton, Hoffhine, and Folkers, J. Am. Chem. Soc., 67, 2092 (1945).

Schmidt, Ber., 52, 409 (1919).

Rosenmund and Langer, Ber., 56, 2262 (1923).

Infinite Radiant Light - THKRA
 
 
 
 
    Vitus_Verdegast
(Hive Bee)
09-11-03 06:09
No 458295
      Preparation of Pd/C using ultrasound
(Rated as: good read)
 Bookmark   

Maybe using ultrasound for precipitating palladium could make the homemade Pd/C catalyst much more potent?
The much smaller particles created by sonification should provide a much larger surface area for hydrogen absorption, n'est-ce pas? wink

Of course only the highest quality of activated carbon should be used.





Preparation of Pd/C catalysts via ultrasound: a study of the metal distribution.


Bianchi, C. L.; Gotti, E.; Toscano, L.; Ragaini, V.   
Department of Physical Chemistry and Electrochemistry,  University of Milan,  Milan,  Italy.  

Ultrasonics Sonochemistry  (1997),  4(4),  317-320.

CAN 128:66888, AN 1998:41122


Abstract

Palladium supported on active carbon catalysts was prepd. using ultrasound during one of the prepn. steps.  An investigation of the metal distribution into the pores of the support was performed both by a deep characterization of the prepd. samples and by a catalytic reaction involving some org. reactants to be reduced. 








Hydrogen spillover within carbon-supported palladium catalyst prepared under ultrasound.


Cheng, Z. X.; Yuan, S. B.; Fan, J. W.; Zhu, Q. M.; Zhen, M. S.   
Department of Chemistry,  Tsinghua University,  Beijing,  Peop. Rep. China.   

Studies in Surface Science and Catalysis  (1997),  112(Spillover and Migration of Surface Species on Catalysts),  261-266.

CAN 128:106832, AN 1998:89933   


Abstract

The Pd/active-carbon catalyst was prepd. in soln. through a redn. of Pd(II) with formaldehyde, and the obtained metallic particles were around 10-30 .ANG. with a mean size about 16 .ANG. either applying ultrasound in catalyst prepn. or varying palladium loading (0.8-5 wt.%). 
H2 spillover from Pd onto the carbon surface could occur in Pd/C at 200C, and H/Pd decreased with the increase of Pd loading; the ultrasound in Pd/C prepn. led to a greatly increased amt. of spillover H2, and H/Pd could reach a high value of 6.8 for 0.8 wt.% sonicated Pd/C catalysts.  The Pd/C activity (mole H2/min.g.Pd) in nitrobenzene hydrogenation at 30C increased with the palladium loading. 




A Dream Within A Dream (http://www.poedecoder.com/Qrisse/works/dreamw.html)
 
 
 
 
    Vitus_Verdegast
(Hive Bee)
09-11-03 06:24
No 458297
      Other supported metal catalysts and ultrasound
(Rated as: good read)
 Bookmark   



A new method to prepare highly dispersed supported metal catalysts.


Bianchi, C.L.; Carli, R.; Lanzani, S.; Lorenzetti, D.; Vergani, G.; Ragaini, V.    Dep. Phys. Chem. Electrochem.,  Univ. Milan,  Milan,  Italy.   

Catalysis Letters  (1993),  22(4),  319-25.

CAN 120:308377, AN 1994:308377


Abstract

On a solid surface the effects of the implosion of the bubbles, created during a sonication run, are commonly used to clean or to erode the surface itself.  Ultrasound was used in order to obtain a ruthenium on alumina catalyst distinguished by a very high value of the dispersion of the metal.  The samples were characterized with different techniques in order to study the influence of the sonication on both the metal crystallites and the support. 







An optimized route for the preparation of well dispersed supported ruthenium catalysts.


Bedrane, Sumeya; Descorme, Claude; Duprez, Daniel.    Laboratoire de Catalyse en Chimie Organique (LACCO),  UMR 6503 CNRS, University of Poitiers,  Poitiers,  Fr.   

Journal of Materials Chemistry  (2002),  12(5),  1563-1567.

CAN 137:133874, AN 2002:299822


Abstract

The prepn. of ceria and ceria-zirconia supported 1 wt.% ruthenium catalysts was optimized to obtain well-dispersed Ru particles.  The influence of the prepn. method and treatment conditions on the final morphol. of the catalyst was investigated.  Ceria-supported catalysts, prepd. by incipient wetness impregnation under ultrasound and further treated under hydrogen, had an optimum metal dispersion.  In fact, H2 chemisorption results and TEM observations demonstrated a large increase in the metal accessibility when impregnation was carried out with ultrasound assistance.  Ceria-supported ruthenium catalysts with dispersion 60% were prepd. 







Manufacture of supported metal catalysts.


Shibabuchi, Noriko; Suzuki, Toshio; Hirota, Kazuo.  (Unitika Ltd., Japan).
Jpn. Kokai Tokkyo Koho  (1999), 5 pp.

JP  11033412
CAN 130:187675, AN 1999:97246


Abstract

Solns. contg. catalytic metals are controlled to pH 5-9, surfactants are added, and then porous materials are dipped in the solns. and then ultrasonically treated for manuf. of supported metal catalysts.  Large amt. of metal catalysts can be uniformly supported







Manufacture of metal-loading catalysts.


Suzuki, Toshio; Kanbashi, Noriko; Hirota, Kazuo.  (Unitika Ltd., Japan).   
Jpn. Kokai Tokkyo Koho  (1998), 6 pp.

JP  10085614
CAN 128:249108, AN 1998:208703   


Abstract

The title catalysts are manufd. by ultrasound treating porous materials with immersing in active metal-contg. solns.  Large amt. of catalytic metals are loaded with good uniformity. 




A Dream Within A Dream (http://www.poedecoder.com/Qrisse/works/dreamw.html)