Catalyst recovery is an important step in downstream processing. Using an appropriate scavenger resin and a rotating bed reactor to deploy it, the recovery is straightforward and effective.
“Transition metals, and in particular palladium, have been of importance for the development of reactions for the formation of carbon-carbon bonds.” - The Royal Swedish Academy Of Sciences, Palladium-Catalyzed Cross Couplings in Organic Synthesis
Many reactions involving the formation of carbon-carbon bonds, for instance the Wacker process, or the Heck, Sonogashira or Suzuki cross-coupling reactions, utilize transition metals as catalysts. With a heterogeneous catalyst, the separation is straightforward (especially when using a rotating bed reactor), but in the case of homogeneous catalysis, the metal remains in the product after the reaction. The catalyst contaminates the product, and also remains a value worth recovering. Both are valid reasons why recovery of the metal is desirable.
Palladium catalysts can be removed from a liquid using scavenger resins, which are conveniently deployed in a rotating bed reactor. In this application note, we remove from an organic solvent Pd(OAc)₂, or palladium acetate, which is a commonly used catalyst. Initially the liquid has a dark red colour, indicating the presence of the catalyst, and after the scavenging it becomes colourless, signifying that the metal has been scavenged onto the resin.
We used 2 mL of the scavenger PhosphonicS SPM32 (200-500 µm) in a rotating bed reactor. 105 mg of Pd(OAc)₂ was dissolved in acetonitrile (50 mL), and the rotating bed reactor was rotated at 1000 RPM. The concentration was determined by spectrophotometry at 400 nm.
98.7% was removed in the first 2 hours, and more than 99.5% was removed in 20 hours.
With a rotating bed reactor, it is also possible to simultaneously deploy a heterogeneous catalyst and a scavenger resin, which can simplify the application of hydrogenation, transfer hydrogenation or similar heterogeneous catalytic reactions.
Industries Pharmaceuticals and Cosmetics
Topics Process Development, Downstream Processing, Chemical Catalysis
Products Complete Starter Kit S2
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