Metals Removal
The inclusion of an article in this document does not give any indication of safety or operability. Anyone wishing to use any reaction or reagent must consult and follow their internal chemical safety and hazard procedures and local laws regarding handling chemicals
Metal catalysis is widely employed in the manufacture of APIs. Typical precious metals used are Pd/Ru/Ir/Pt and base metals Ni/Cu/Fe/Sn ( Sn falling out of use recently) – see reviews below:
Chem. Rev., 2011, 111, 2177–2250 Large-Scale Applications of Transition Metal-Catalyzed Couplings for the Synthesis of Pharmaceuticals
Chem. Soc. Rev., 2013, 42, 9283 C–N bond forming cross-coupling reactions: an overview
OPRD, 2010, 14, 30–47 Practical Aspects of Carbon-Carbon Cross-Coupling Reactions Using Heteroarenes
The use of metal catalysts, especially homogeneous metal catalysts requires attention to efficient removal of the metal post reaction. Removal of the metal from the product (and process streams) is important for several reasons:
- Most precious metals and heavy metals are toxic and subject to strict limits in APIs
- Most precious metals and heavy metals are ecotoxic and should not be discharged into the environment.
- Waste contaminated with metals is expensive to treat
- Redox active metals can catalyse unwanted chemistry downstream from desired metal-catalysed step
- Metals can contaminate reactors and other processing equipment
- Metals, especially precious metals have high LCI supply routes and should be recovered and reused.
- The economics of processes using precious metals may dictate metal recovery and reuse.
- Many stocks of precious metals are at medium to high risk of depletion and stocks in use need good stewardship
Elements at Risk of Depletion
British Geological Survey Risk List 2011. www.mineralsuk.com