Plasma-Assisted Non-Oxidative Coupling of Methane in a Dielectric Barrier Discharge Reactor: Effect of Non-Catalytic Glass Materials

A coaxial dielectric barrier discharge (DBD) as a non-thermal plasma reactor was utilized for the non-oxidative coupling of methane into higher hydrocarbons under ambient conditions. The DBD reactor was subsequently performed as a packed-bed dielectric barrier discharge using non-catalytic materials, including glass beads, glass wool, and glass capillary, which were introduced to investigate the non-catalytic reaction mechanism. Typical observation demonstrated that the dielectric glass materials packed with DBD might successfully activate the stable C–H bond to produce hydrogen and C₂–C₄ higher hydrocarbons without the application of any oxidants and additional thermal energy. Among the packing materials investigated, the DBD reactor packed with a glass capillary obtained a maximum CH₄ conversion of 6.1%, with the energy efficiency reaching a maximum of 0.66 mmol kJ⁻¹ at a discharge power of 1.38 W with an SEI of 4.14 J mL⁻¹. The enhanced CH₄ conversion was attributed to an alternation in the plasma discharge behavior with non-catalytic glass materials. Moreover, under these conditions, the low temperature of the discharge zone resulted in minimal solid carbon accumulation on the inner electrode surface of the plasma reactor.