A Technology on the Upswing
André de Vries, commercial director, Innosyn
There are a number of drivers to implement flow chemistry processes over batch operations.
Firstly, a very much improved heat and mass transfer. Millimeter-sized tubular reactors have a much higher surface-to-volume ratio than batch vessels, intensifying heat and mass transfer dramatically. Highly exothermic reactions can be executed (almost) isothermally.
Secondly, a safe operation of hazardous and unstable reagents. Thanks to a continuous operation the volumes of flow reactors are typically several magnitudes smaller, and there is no, or hardly any, hold-up of these unstable compounds.
Thirdly, the operating window can be beyond “normal”, especially temperature and pressures, allowing the safe use of for example toxic gases, previously avoided on large scale. Also superheating of common low-boiling solvents to speed up the reaction kinetics can be executed safely.
And finally, process monitoring and control is improved with continuous processing, leading to a lower level of impurities.
Implementation of flow chemistry processes, however, is hampered by the already widely available batch vessels of all kind of sizes and a well-established culture to run chemical processes in such assets. In addition, many chemical products are being used in a heavily regulated domain, with tight specs, and any change in production process will lead to new validations and alike. To overcome some of the hurdles Innosyn is using 3D metal printing (selective laser melting), as method of choice for manufacturing the most fit for purpose reactors for flow chemistry processing. This technique gives maximum flexibility to introduce specific features like static mixer elements and temperature probe inlets; one can iterate designs rapidly to tailor to the specific chemistry at hand; and is cost-efficient since only the metal ending up in the reactor is consumed.
We see the use of flow chemistry processes being applied successfully, especially in those fields where it can make a severe difference compared to batch processing. In practice this entails any sort of organometallic chemistry, and the safe use of hazardous reagents and reaction mixtures, enabling shortcut routes to special chemicals, alternatively produced by lengthy routes preventing the use of those hazardous compounds.