(314a) Simultaneous Activation of CH4 and N2 in a Microwave Enhanced Plasma-Catalytic Hybrid Reactor

Plasma afterglows are widely studied in applications such as nitriding, nitrocarburizing, detoxification of gases, simulating planetary atmospheres and chemical processing. The direct ignition of CH₄ gas within the waveguide region, to plasma state requires high pressure or vacuum conditions leading to a very high carbon soot formation, which can only be controlled by co-feeding H₂. Additionally, the power requirement can be as high as 800 W at atmospheric pressure. In this work, a stable and continuous MW enhanced Argon (Ar) plasma was generated at atmospheric pressure and power at 550 W. The plasma afterglow region was utilized to active CH₄ and N₂. The activation of the reactive gases in the afterglow region offered several advantages:

• The region is usually cold at atmospheric pressure leading to methane activation without excessive coking.
• The feed gas (Ar) used to generate plasma can be continuously exposed to the waveguide leading to a stable plasma generation.
• The reactive species do not alter the power requirements, which is usually the case when the reaction occur in the waveguide region.
• The coolant flow rate can be fixed for the same reason.

The conversion of CH₄ in the plasma afterglow region was reported to be 20% with C₂H₂ (0.5% by volume) and H₂ (1.8% by volume) as major products and negligible carbon soot deposit. Cs promoted RuO₂ supported on Ceria was then placed within the plasma afterglow region and heated thermally to 180 ⁰C. A steady production of 20 ppm of NH₃ was observed while C₂H₂ was selectively hydrogenated to C₂H₄ (0.01% by volume).

In conclusion, this plasma-catalytic system successfully demonstrated the direct conversion of Methane and Nitrogen to Ammonia and Ethylene. This new hybrid method increase the scope of direct and non-oxidative methane conversion, paving out new ways for stranded natural gas utilization.