Direct conversion from methane to methanol for high efficiency energy system with exergy regeneration

Direct synthesis of methanol from methane and water vapor mixtures has a high possibility to realize a highly sophisticated energy recycling system with exergy regeneration. Because, combined with a reforming process from methanol to hydrogen, exergy rate of low temperature thermal energy sources at about 100 °C can be enhanced to high quality chemical energy in hydrogen. For realizing this newly proposed energy system, direct synthesis of methanol from methane and water-vapor mixture has been successfully realized by non-equilibrium plasma chemical reactions under atmospheric pressure using a newly developed ultra-short pulsed barrier discharge in an extremely thin glass tube reactor. Various effects of reaction time, water-vapor concentration and discharge parameters on the conversion efficiency and reaction selectivity have been clarified. Methanol yield has reached the order of 1% at the water-vapor concentration of about 50%, and it has been proposed that the value can be largely enhanced by adding rare gas such as Kr or Ar to the source gas. Possible mechanisms for this effect have been also discussed.