Elking_around
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Catalyst preparation dumb question
Hello my fellow humans,
Upon researching catalyst preparation, I thought I had figured out that the metal load is on the entire weight of the catalyst.
For example, if one wants 100g of 10% Pt/C, one would use 10g of Pt with 90g of the acid washed carbon; 100g/10g = 10%.
The thing is, most preparations that I came across (references below), often claim to be say 5%, but when calculated with the method above, always
indicate to be more. The same thing applies to 10% and 30% preparations.
So far I'm assuming that it's some sort of margin or "to be safe" extra, but I also believe I may not know all that much after all.
If anyone has opinions or references, I would be more then happy to read them. Unfortunately, I could only find preparations from the Erowid archive
and less dignified sources. The pdf below has all the preparations found in the former. (Thank you Rhodium, perhaps someday I’ll be able to make
some good margarine...)
Palladium on Carbon (5% Pd/C) [1] {1.7g PdCl2 / 21.7 = 7.8%}
Prepare a solution of 1.7 g of Palladium Chloride (or an equimolar amount of palladium chloride dihydrate, PdCl2*2H2O) in 1.7 ml of concentrated
hydrochloric acid and 20 ml of water by heating on a water bath for 2 hours or until solution is complete, and add this to a solution of 30 g of
sodium acetate trihydrate (Note 1) in 200 ml of water contained in a 500ml hydrogenation flask. Add 20 g of acid washed activated charcoal (Note 2)
and hydrogenate in an atmospheric hydrogenation apparatus until absorption ceases. Collect the catalyst on a buchner funnel and wash it with five 100
ml portions of water and suck dry as possible. Dry the catalyst at room temperature over potassium hydroxide pellets or anhydrous calcium chloride in
a vacuum dessicator. Powder the catalyst (approx 20 g yield) and store in a tightly stoppered glass bottle.
[1] R. Mozingo, Organic Synthesis Collective Volume 3, 685 (1955)
Alternate procedure [2] {0.5g PdCl2 / 8 = 6.25%}
Heat 7.5g activated charcoal (Note 2) on a steam bath for 2-3 hours with conc. hydrochloric acid (5 ml) and water (150ml). Wash the charcoal by
decantation with hot water until free of acid, filter it off, and dry it in an oven below 100°C.Heat 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). 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 tightly stoppered bottle.
[2] Vogel's Textbook of Practical Organic Chemistry, 5th ed, p 452-460 (1989)
Attachment: Palladium~Platinum Catalyst Preparation FAQ.pdf (120kB)
This file has been downloaded 87 times
[Edited on 30-1-2023 by Elking_around]
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Sulaiman
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molecular weights
Anhydrous
Pd/PdCl2 = 106.42/177.326 = 0.6
Dihydrate
106.42/213.357 = 0.5
CAUTION : Hobby Chemist, not Professional or even Amateur
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Mateo_swe
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Do you have a Parr hydrogenator?
Hydrogenations are a quite complex procedure, you should have a bit of experience before trying this out.
Chemically its quite straightforward but the handling of pressurized hydrogen connected to a flask that is fitted with heating and also needs shaking
during the procedure.
But maybe you have experience with these things or have someone that help you that have done this before.
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Elking_around
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Sulaiman: Interesting, thank you for the clarification. While doing a bit of math, I would then assume that molecular weights are not used outside of
calculating the original mass of the unmodified metal. You've cleared up any doubts I had.
Mateo_swe: My wallet happens to be quite empty, sadly.. Although I have been working hard trying to not blow myself up. I'm aware of the basic need to
purge multiple times with N2, Ar, etc.. prior to adding the catalyst while under a blanket of that inert gas. Then gradually doing the same with H2,
pressurizing say 1/3, vacuum out, then 2/3 and out followed by the required pressure/constant flow. Using safety valves for pressure release and
against flashbacks while owning 2 ABC powder fire extinguisher. (I really loooves margarine..)
[Edited on 30-1-2023 by Elking_around]
[Edited on 30-1-2023 by Elking_around]
[Edited on 30-1-2023 by Elking_around]
[Edited on 30-1-2023 by Elking_around]
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Texium
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Please knock off this annoying third person nonsense.
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Elking_around
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jeez okay, sorry, I didn't think it would be this bad. I've updated the posts..
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Texium
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It’s alright, thank you for editing them. You’ll find you make a better impression here when you are forthright in your posts rather than trying
to be “quirky.” With that out of the way, welcome to the forum.
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