NTP-assisted partial oxidation of methane to methanol: effect of plasma parameters on glass-packed DBD

The partial oxidation of methane to methanol was performed in a non-thermal dielectric barrier discharge (DBD) plasma reactor. The influence of various parameters on the conversion of methane, product selectivity and energy efficiency has been studied. Typical results indicate that the discharge gap has a marked influence on methane conversion and product distribution. The best selectivity to CH3OH and HCHO was similar to 25% and similar to 17% at a discharge gap of 4.5 and 5 mm, respectively, and the highest corresponding energy efficiency was similar to 0.9 mmol kJ(-1). At a later state, the DBD reactor was operated under a packed-bed configuration by integrating the discharge gap with zero surface glass materials having different geometry: glass beads (spherical), glass capillary (hollow cylindrical) and glass wool (spongy honeycomb) to understand the influence of material geometry on the plasma discharge and finally on the formation of products such as CH3OH, HCHO, CO, CO2, H-2, C2H6. Typical results indicated that the morphology of the packing materials affects the discharge characteristics, and hence the product distribution. It is concluded that the better performance of the packed-bed plasma reactor is due to the improved electrical field strength. Among the geometries studied, glass wool showed the highest CH4 conversion due to the improved field strength/surface corona, whereas glass-bead packing improved the CH3OH selectivity to similar to 32%.