Just finished reading an excellent example from a group in Japan moving a batch hydrogenation to flow. Dr Sajiki’s group developed and evaluated a number of Pd-catalysts and their effectiveness in an H-Cube (Thales Nano) reactor. This evaluation went into detail on both reaction optimization and chemoselectivities, depending on the catalyst type — while scoping a variety of temp, flow and solvents for each of the reactions — it was truly impressive how much work was performed and the amount of information we obtain for the work done. The work was published in Tetrahedron 2014 and featured and a highlight brief in Synfacts 2014.
From the cartoon below, you can see that the substrate was passed through a series of immobilized Pd catalysts to provide different targets depending on their functionality. A variety of pressures, flow rates, and substrate concentrations were studied as part of the optimization process.
Rather than going into all of the reaction conditions, I have included a table illustrating the hydrogenation of benzophenone on one-pass with different solvents and temps with 1 bar H2. Clearly the instrument is designed to handle high temp and high pressure, but this is a quick look into how easy it is on the experiment side. Further reading will provide a complete picture of their work. Happy reading!