(8a) Comprehending Methane Activation for Plasma–Liquid Systems in a Dielectric Barrier Discharge (DBD) Microreactor Chip

Methane conversion using both dielectric barrier discharge (DBD) plasma and microfluidics offers a promising solution for pertinent decarbonization efforts by valorizing greenhouse gases. DBD plasma-based reaction technology has its edge in facilitating radical formation in atmospheric conditions, versatile compatibility with a wide spectrum of materials, and viable scalability. On the other hand, using microreactors enables efficient heat and mass transfer, safety, and control of operating parameters. Thus, the use of microfluidic plasma plays a key role in the current paradigm shift from batch to continuous synthesis technologies, especially in the fine and specialty chemical sectors. Despite the prevalence of gas-only reaction systems in DBD-plasma-based methane conversion studies, including organic liquids presents numerous research opportunities across diverse fields, potentially leading to sustainable production of desired products. However, understanding the effect of parameters like electrical energy, thermochemical properties, and multiphase flow patterns remains a challenge. The interaction between organic liquids and methane plasma is an unexplored area. In this study, experiments have been conducted using methane and various common organic solvents in an in-house developed DBD microreactor chip. The chip, with a square cross-section of 500 μm×500 μm, was fabricated on a silicon wafer, with channels sealed using Borofloat 33 glass. A nanosecond pulse generator provided the necessary electrical power for plasma formation. The study focuses on analyzing the effect of operating parameters such as potential difference, pulse width, and liquid properties on methane activation in a plasma-liquid microfluidic system. Optical emission spectroscopy, electrical calculations, and thermal imaging were combined to estimate methane activation thresholds and understand plasma-liquid behavior. Reaction performances were assessed, and product profiling was conducted via mass spectroscopy. Results indicate that high liquid hold-up, low boiling point, and low dielectric constant of organic liquid adversely affect plasma formation and methane activation.