Molecular oxygen is a green, inexpensive and very abundant oxidant on earth. Until recently, classical oxidations were executed using toxic (in)organic oxidants such as CrO3, KMnO4, MnO2, activated DMSO (Dimethyl sulfoxide) and bleach. Recent social concerns regarding the environmental impact and sustainability of chemical processes have shifted the attention to green alternatives. O2 fits this role perfectly, as it is readily available, non-toxic, and displays high atom economy in oxidation reactions.
New advances in reactor technologies have made it possible to perform continuous aerobic oxidations in flow reactors. Performing chemistry in continuous flow reactors offers significant improvements over batch reactors regarding mixing, heat transfer, ease of pressurization, scalability, and more (Gavriilidis et al., 2016). The exothermic nature of aerobic oxidations can be controlled using the superior heat transfer of flow reactors , and the oxygen pressure in the reaction medium can be easily increased to increase the oxygen concentration, thus boosting reaction productivity.
In order to operate safely the continuous aerobic oxidation of acetonitrile and oxygen inside the micro 3D-printed reactors at elevated pressures and temperature, a safety study was performed. 3D-printed reactors can safely withstand up to 100 bar system pressure. The safety tests were performed in an autoclave filled with 5 gr of pure acetonitrile and pressurized with a respective oxygen pressure of 20, 48 and 102 bar. The autogenous ignition temperature (AIT) was determined according to ISO 11114-3 at different conditions as a safety limit for the continuous flow set-up.