(419e) Ultrasound As a Process Intensification Tool in Small-Scale Reactors

Small-scale flow reactors support the shift in chemical manufacture towards green and sustainable processes, especially since the small reactor length scales enable the transition to chemical activation via renewable energy sources, e.g. photo- and electrochemistry [1,2].

Nevertheless, there is still intensification potential for both processes. Photochemistry is often performed in two-phase flow, and the presence of a non-absorbing phase significantly reduces the photochemical efficiency. In a preliminary study, we developed a multizone photochemical reactor model which predicts that the largest reactivity is observed in the vicinity of the dispersed phase, and not in the bulk liquid slug in Taylor flow [3]. Thus, to further enhance the reactor efficiency and to increase its throughput the two-phase contacting pattern needs to be better controlled. Similar optimization potential is also present for electrochemical microreactors: As the flow is laminar diffusion is the only mechanism by which electroactive material reaches the electrodes. In a preliminary study we created an operation regime map of parallel plate electrochemical microreactors based on literature published since 2000, which clearly revealed that the throughput in electrochemical reactors is imposed by diffusion mass transfer limitations [4]. Consequently, to further intensify electrochemical flow reactors and to go beyond the diffusion limits, active mixing is necessary.

In this talk I will present our recent approaches to use ultrasound actuation to overcome the aforementioned transport limitations. We focus on a holistic approach to exploit acoustic resonance and characterize the synergistic effects of ultrasound in electro- and photochemical reactions.

References

[1] Hoffmann, N. (2012) Photochemical & Photobiological Sciences 11, 1613-1641.

[2] Lund, H. (2002) Journal of The Electrochemical Society 149, S21- S33.

[3] Roibu, A., Van Gerven, T. & Kuhn, S. (2020) ChemPhotoChem 4, 5181-5192.

[4] Fransen, S., Ballet, S., Fransaer, J. & Kuhn, S. (2020) J. Flow Chem. 10, 307–325.