Partial oxidation of methane to methanol in a newly developed selective discharge plasma reactor

Abstract

Summary form only given. A selective discharge plasma reactor was developed and used to produce methanol from methane and nitrous oxide. The product distribution in the reaction depended on the activated reactant molecules. The selectivity to partial oxidation products such as methanol and formaldehyde increased when methane was excited and nitrous oxide was unexcited. Furthermore, the position where a reactant could contact the other one was a very important factor in effective methanol and formaldehyde production. Methanol is an important material from the point of view as a gasoline additive and as an automobile fuel. The partial oxidation of methane to methanol is desirable if high selectivity to methanol and reasonable conversion rate can be obtained. We were reported partial oxidation of methane with nitrous oxide in dielectric barrier discharge plasma, previously. In this report we show a newly developed dielectric barrier discharge (DBD) plasma reactor that can excite the reactant, selectively. The selective excitation DBD plasma reactor was basically similar to that of Chen et al. An Al tube was used as internal electrode (6mm od) that was supported in the center of quartz tube (10mm id, 200mm length) with the other Al tubes. Outer surface of the quartz tube was tightly covered by Cu foil as external electrode. Some reactants could flow along the inside of inner electrode and go out through small holes located on the electrode, and react with other gases on the surface of the electrode. Other reactants could flow between both electrodes, then be excited by electrons. High voltage electricity was applied to both electrodes by a high voltage power supply. The conversions of methane and nitrous oxide in the selective plasma reactor decreased in comparison with those of normal DBD plasma reactor. However, selectivity to methanol and formaldehyde reached ca. 30% while nitrous oxide was selectively excited by plasma. In this case, main product was carbon monoxide. On the other hand, no methanol formed while methane was selectively activated by plasma. Predominant reaction in this case was dimerization of methane molecules. From these results, it was clear that the selective excitation DBD plasma reactor could work well in this reaction.