dormouse (Member)
04-25-00 01:23
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      EZ Preperation of 5% Pd/C -KrZ  Bookmark   


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Author  Topic:   EZ Preperation of 5% Pd/C 
KrZ
Hive Bee   posted 02-15-2000 09:51 PM           
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Place the following in a 1L beaker;
500ml 31.45% HCl
120g Powdered Activated Charcoal
10g PdCl2
Stir the mix vigorously with a stir rod for a few minutes. Now begin boiling down the mix, as the volume decreases and the mix begins to thicken slow the heating until (when you near the end) there is a slow but steady evaporation. Stop while the mix is still a sludge, place everything in a vacuum dessicator (or just a tupperware box with some DrieRite in it, takes longer) and leave until it is dry. The dry powder you have is ready to go, although a pre-reduction (activation period) is needed/recommended. Yield = 120g of 5% Pd/C.

Prereduction
Place the catalyst in the solvent to be used, remove atmosphere and pressurize with hydrogen. Allow to stir as long as you care to, longer the better! Remove the hydrogen and add your reactants and go from there. Even catalysts which say they need no prereduction can benefit from it = greater yields in shorter times!

Source: Organic Syntheses, Colected Vol. 3 p.685


Osmium
PimpBee   posted 02-16-2000 07:42 AM           
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Have you tried the formaldehyde reduction of a stirred PdCl2/carbon suspension? It's in Org. Synth. too. Which one is better suited for ghetto style cooking?
 
KrZ
Hive Bee   posted 02-16-2000 09:27 AM           
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The CHO method looked a little more annoying, although this method produces a catalyst that requires a longer prereduction period than the CHO calayst (which will work fine w/o activation, while the other catalyst definitely needs a good hour or so to warm up) I think the best ghetto method is Steal a Pd coin from the local jewlery store, using a plastic knife and ski-mask, powder it, convert to PdCl2 and then use this method
 
dwarfer
Hive Bee   posted 02-16-2000 03:44 PM           
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Good info KrZ: I'm about out of my 10 gram bottle. (And that Gemini bottle is "hard" on the catalyst.)
[But I gotta fix for it coming up]

I'll try Ni first because it's easy, but its good to have a back up to my back up.

Hey, if you can add some value to my question in the General section on palladium prices, I'd be appreciative.

regards
dwrfr


essncee
NewBee   posted 02-16-2000 06:26 PM           
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I tried powdering a Pd coin with a plastic knife while wearing a ski mask... no luck.
Used the search engine. Nothing on Plastic knives or ski masks
any suggestions? (oh oh  )
 
Foxfire
NewBee   posted 02-18-2000 11:44 AM           
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This may be of interest to some. http://www.ch.ic.ac.uk/local/organic/12.html 

Adam's Catalyst
In a fume cupboard, dissolve chloroplatinic acid (H2PtCl6.6H2O, 0.10 g) in water (ca. 0.5 ml) in a porcelain crucible (3-4 cm diameter). Add sodium nitrate (1 g) and evaporate the mixture to dryness, over a low flame, with continuous stirring. Turn the Bunsen burner full on and stir the contents of the crucible vigorously until the mass has melted completely and the initial decomposition has subsided. Keep the bottom of the crucible at a dull red heat for a further 30 min. (too strong a heat decomposes the oxide to the metal). Allow the crucible to cool and wash the contents into a 250 ml. beaker with hot water from a wash bottle. Filter off the brown platinum oxide with a small ('Hirsch') funnel (Whatman paper No. 541) and wash the oxide with hot water (about 200 ml) until the washings are free from nitrate ion. Dry the catalyst over calcium chloride in a vacuum desiccator.

Palladium Black
Heat a mixture of palladium chloride (0.50 g) and water (100 ml) to 80deg.C and carefully neutralise the suspension, to wide-range indicator paper, with 20% sodium hydroxide solution (if the end point is overshot, palladium hydroxide precipitates). Add 2.6% formic acid (2.5 ml) and, after about 2 min. make the solution strongly alkaline with 20% sodium hydroxide solution (5 ml). Add more of the formic acid (5 ml) and make sure that the solution is still alkaline. Heat the mixture on a steam bath for 2 hours. Filter off the precipitate with a small ('Hirsch') funnel (Whatman filter paper No. 541), wash it free from alkali and dry it over calcium chloride in a vacuum desiccator.


5% Palladised Charcoal
Heat decolourising charcoal (7.5 g) on a steam bath for 2-3 hours with conc. hydrochloric acid (5 ml) and water (150 ml). Wash the charcoal by decantation with hot water until free of acid, filter it off, and dry it in an oven at <100deg.C.
Warm palladium chloride (0.5 g) in conc. hydrochloric acid (0.75 ml) and water (5 ml) on the steam bath for ~ 20 min. Add the solution to AnalaR sodium acetate (17.5 g) in water (50 ml) contained in a hydrogenation flask. Introduce the purified charcoal (5.8 g) and hydrogenate the mixture until no more hydrogen is absorbed (~ 2 h). The hydrogenation procedure is described below. Collect the catalyst on a 7 cm Buchner filter (3 thicknesses of Whatman No. 1 filter paper), wash it with water (5 x 100 ml) and drain it on the filter with suction. Dry the catalyst over fresh silica gel in a vacuum desiccator and store it in a tight stoppered bottle.


Lindlar's Catalyst (5% Pd on CaCO3, poisoned with Pb)
Stir calcium carbonate (precipitated, light; 1.1 g) in water (10 ml) in a flask which is fitted with a thermometer and mounted on a magnetic stirrer/hotplate. Whilst continuing the stirring, add palladium chloride (90 mg) to the suspension and after 5 min., raise the temperature to 80deg.C for a further 10 min. Cool the mixture and transfer it to a hydrogenation flask, using ~ 10 ml of water for rinsing. Hydrogenate the mixture until hydrogen absorption (10-20 ml) is complete (ca. 15 min); the hydrogenation procedure is described below. Collect the reduced catalyst on a small 'Hirsch' funnel (Whatman filter paper No. 1) and wash the catalyst with distilled water (20 ml). Add the damp catalyst to distilled water (10 ml) in a flask on the magnetic stirrer/hotplate. Switch on the stirrer, add a 5% (w/v) solution of AnalaR lead acetate in water (2 ml) and, after 10 min., raise the temperature to 90deg.C for 40 min. During this time, add distilled water, as necessary, to compensate for evaporation losses. Cool the mixture, collect the catalyst on Whatman No. 1 paper in a small 'Hirsch' funnel and wash the catalyst with distilled water (total, ~ 50 ml). Transfer the catalyst to a clean, tared, specimen tube and dry the catalyst in a pistol at 40deg.C to constant weight (~ 1-3 h). Crush the dry catalyst to a powder with a clean spatula or glass rod and stopper and label the tube (catalyst yield: 0.9-1 g).


 
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