Baphomet - 14-2-2007 at 20:11
Literature on the subject advises to add dilute acid to the reaction medium before attempting to separate the product. It is claimed the acid would
help the catalyst to 'crash out' and make extraction easier.
However, on reflection, would it not make more sense to add an alkali? My theory is based on a reaction vessel containing a mix of:
* Organics
* Water
* Ethanol
* Acid
* Pd / PdCl2
* Cu / CuCl2
Ketones & some other organics react with strong bases but what would be wrong with adding 10% NaOH? It would allow easy recovery of an expensive
catalyst that would otherwise be (partially) in solution, viz.:
* Organics (hopefully unchanged)
* Water
* Ethanol
* Pd
* Cu
* NaCl
Baphomet - 17-2-2007 at 21:52
OK I found out why, first-hand. Dilute NaOH (5% w/v) created a thick goopy emulsion which trapped product and made filtering & extraction a bitch.
So, I shall question the references no more! 
stoichiometric_steve - 12-4-2008 at 10:08
is it even remotely possible to recover the catalyst (i.e. PdCl2) from wacker oxidations employing Benzoquinone, or molecular oxygen?
i've never performed this kind of reaction so i don't know whats going on, except for the shitty workup quoted in every source using Benzoquinone.
leu - 13-4-2008 at 17:34
This patent describes a method for recycling palladium:
US 3,210,152
Regeneration of Metal-Containing Reaction Components and Process for the Production of Palladium Chloride
This invention relates to the regeneration of metal containing components comprised in reaction mixtures employed in the
execution of organic reactions. The invention relates more particularly to the regeneration of reaction mixture components comprising a metal of the
palladium or platinum groups, which metal has been converted from a higher to a lower valent state during the course of execution of an organic
reaction.
Compounds of metals of the palladium and platinum groups find application in the execution of organic reactions of varying types. During the course of
use, at least a part of the metal component is converted from a higher to a lower valent state. Since these metals are relatively costly, the
practicability of such processes is often dependent upon ability to regenerate the reaction mixture component comprising the metal in its initial
higher valent state. The regeneration procedure must be carried out efficiently with a minimum of operative steps. It must furthermore lend itself to
continuous operation and preferably in a manner capable of efficient integration with the execution of a desired organic reaction.
[Edited on 14-4-2008 by leu]
Attachment: US3210152A1.pdf (528kB)
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leu - 13-4-2008 at 17:38
Impurities in the gas charge contribute most to catalyst degradation, another process for regeneration of wacker oxidation catalysts is in Patent
DE1143499. This method is applicable to the reduced palladium recovered by filtration, or the reduced catalyst that tends to adhere to labware 
Attachment: DE1143499B1.pdf (227kB)
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