Effect of packing material on methane activation in a dielectric barrier discharge reactor

The conversion of methane is measured in a planar-type dielectric barrier discharge reactor using gamma-Al2O3 (sphere), alpha-Al2O3 (sphere), and gamma-Al2O3 (16-20 mesh). Investigations on the surface properties and shape of the three packing materials clearly indicate that methane activation is considerably affected by the material used. Capacitances inside the discharge gap are estimated from charge-voltage plots, and a comparison of the generated and transferred charges for different packing conditions show that the difference in surface properties between gamma- and alpha-phase Al2O3 affects the discharge characteristics. Moreover, all packing conditions show different charge characteristics that are related to the electron density. Finally, the packing material's shape affects the local electron temperature, which is strongly related to methane conversion. The combined results indicate that both microscale and macroscale variations in a packing material affect the discharge characteristics, and a packing material should be considered carefully for effective methane activation. (C) 2013 AIP Publishing LLC.