Dilution effect with inert gas in direct methanol synthesis from methane using nonthermal plasma

Direct methanol synthesis from CH₄ and O₂ has been experimentally studied using pulsed discharge plasma in a concentric-cylinder-type reactor. The methanol production was enhanced by dilution of source gas with inert gas, such as Ar, He. The methanol production became about 2.5 times larger at the dilution ratio of 2.5, and gradually decreased with increase of the dilution ratio, resulting in decrease of O₂ partial pressure. C₂H₆ was formed as one of the by-products, and its concentration increased with increase of the dilution ratio. This tendency was the same for Ar and He. Where the partial pressure of O₂ was kept constant, on the other hand, the methanol production increased and saturated the increasing the dilution, but concentration of C₂H₆ stayed at about the same level. Reaction selectivity of the methanol synthesis depended on the dilution ratio of the inert gas