(262b) Plasma-Liquid Interfacial Interactions in Multiphase Microreactors

The utilization of dielectric barrier discharge (DBD) multiphase microreactors exhibits potential to probe the reactivity between plasma and liquids [1]. This idea is bolstered by the prospect of establishing a constant fluid-fluid interfacial profile between the plasma and liquid. However, the fluid-fluid reactions parallel the challenges in mass-transfer limitations in multiphase microreactors. Plasma generation, under ambient temperature and atmospheric pressure, is feasible with AC voltage application to indium tin oxide (ITO) electrodes separated by dielectric materials. Micro-plasmas can be generated in this way in the presence of strong electric fields. This results in the generation of highly reactive gaseous radicals within the microchannels that are in between the dielectric sheets, which then can be used in chemical reactions.

Four different DBD multiphase microreactors were designed and fabricated out of silicon and borosilicate glass to measure the fluid-fluid reaction kinetics as a bulk mixture and as a discrete fluid-fluid interface. In these microreactors, conditions such as the voltage applied for electrical field formation, volumetric flowrates of the fluids, time of reaction, concentrations of reagents, and fluidic pressure can be readily controlled with respective apparatuses. Mass transport limitations at the plasma-liquid interface, as well as the fluid-fluid reactivity, will be presented and discussed in the context of, (i) Plasma formation in a gas-liquid bulk mixture, (ii) Relatively small liquid volumes enveloped by gaseous radicals, (iii) Gaseous radical diffusion driven transport at a discrete plasma-liquid interface, and (iv) Gaseous radical advective driven transport at a discrete plasma-liquid interface. Monitoring by in-situ optical emission spectroscopy of the plasma-fluid phase behavior in these multiphase microreactors will be presented. Plasma micro-reaction engineering creates the opportunity for flash chemistry that parallels many of the same advantages as traditional microreactors.

References:

1. Wengler, Julien, et al. doi:10.1039/c8re00122g.
2. Pipa, Andrei, and Ronny Brandenburg. doi:10.3390/atoms7010014.