Platinum on carbon catalyst via reduction by formate
Hello everybody,
Usuall procedure concerning the preparation of platinum or palladium catalysts involves the reduction of Pt or Pd compounds (ex: palladium chloride or
hexachloroplatinic acid) in presence of activated carbon with formaldehyde in basic conditions
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Palladium on carbon catalyst (5% Pd). A suspension of 93 g. of nitric acid-washed Darco G-60 (Note 10) in 1.2 l. of water contained in a 4-l. beaker
(Note 3) and (Note 4) is heated to 80°. To this is added a solution of 8.2 g. (0.046 mole) of palladium chloride in 20 ml. (0.24 mole) of
concentrated hydrochloric acid and 50 ml. of water (Note 2). Eight milliliters (0.1 mole) of 37% formaldehyde solution is added. The suspension is
made slightly alkaline to litmus with 30% sodium hydroxide solution, constant stirring being maintained. The suspension is stirred 5 minutes longer.
The catalyst is collected on a filter and washed ten times with 250-ml. portions of water. After removal of as much water as possible by filtration,
the filter cake is dried (Note 11), first in air at room temperature, and then over potassium hydroxide in a desiccator. The dry catalyst (93–98 g.)
is stored in a tightly closed bottle.
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From http://www.orgsyn.org/demo.aspx?prep=cv3p0685
The formaldehyde can also in some case be replaced by the formate ion as a reducer :
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The process of reducing [PtCl6]2- ion by sodium formate includes a number of consecutive stages: Pt (IV) -> Pt(II)-> Pt:
the higher the (Cl-) concentration, the slower the process rate; the activation energy for the interval of 95-60°C is of 105kJ/mol.
The fractional conversion of the metal to powder achieves 99.9% in processing of chloro-amine compounds of platinum and palladium in sodium hydroxide
solution by reducing agents (sodium formate, aluminum, hydrazine salts).
Platinum niello is produced by reaction of ammonium hexachloroplatinate with 2.5M solution of formic acid or sodium formate at 102 +/- 5°C; pH of
6.0-6.5 is supported with the help of NaOH (or NH3).
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https://books.google.fr/books?id=6aP3te2hGuQC&pg=PA430&a...
Page 430, Chemical reduction
Having some hexachloroplatinic acid, activated carbon (surface area specified at 1000m²/g) and formic acid, and in order to prepare some Pt/C, I
would like to adapt the later procedure to reduce ammonium hexachloroplatinate (so basically just add the amount of activated carbon in the solution).
Would the ending catalyst will be comparable with a Pt/C prepared by the reduction with formaldehyde ? (surface area, homogeneous deposition on the
substrate...)
I will post pictures of the procedure to see if the reaction goes well
Thanks for your advices
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