Use of Catalytic Static Mixers for Continuous Flow Gas–Liquid and Transfer Hydrogenations in Organic Synthesis

Catalytic static mixers were used for the continuous flow hydrogenation of alkenes, alkynes, carbonyls, nitro- and diazo-compounds, nitriles, imines, and halides. This technique relies on tubular reactors fitted with 3D printed static mixers which are coated with a catalytic metal layer, either Pd or Ni. Additive manufacturing of the metal mixer scaffold results in maximum design flexibility and is compatible with deposition methods such as metal cold spraying which allow for mass production and linear process scale up. High to full conversion was achieved for the majority of substrates, demonstrating the flexibility and versatility of the catalytic static mixer technology. In the example of an alkyne reduction, the selectivity of the flow reactor could be directed to either yield an alkene or alkane product by simply changing the reactor pressure.