(292e) Direct HCN Synthesis Via Plasma-Assisted Conversion of Methane and Nitrogen

Wasteful loss of methane (CH₄) is reported in remote locations, either in the form of CH₄ emissions or flare gas. Plasma-assisted hydrogen cyanide (HCN) synthesis from dilute CH₄ streams is a promising route to methane feedstock underutilization. The potential of dielectric barrier discharge (DBD) nitrogen (N₂)/CH₄ plasma for decentralized catalyst-free selective HCN production at ambient temperature conditions paired with renewable energy sources, renders it compelling compared to existing processes. In this work, we evaluate the suitability of N₂/CH₄ DBD plasma for selective HCN production, investigating the correlation between operating parameters, HCN and ethane (C₂H₆) yield and energy consumption (E_HCN). We demonstrate that HCN selectivity is favored by low initial CH₄ concentration. For further insight into parametric effects on radical induced chemistry, we develop a microkinetic model, establishing that a simplified reaction network with a significantly reduced number of active plasma species can reliably replicate yield trends. We then discuss the reactions and crucial intermediates governing HCN and C₂H₆ synthesis across experimental conditions. Finally, we compare this process to current industrial ones, regarding E_HCN and CO₂ equivalent emissions, showing that N₂/CH₄ DBD plasma can achieve minimal CO₂ emissions.