Direct HCN synthesis via plasma-assisted conversion of methane and nitrogen.

Hydrogen cyanide (HCN) is synthesized from ammonia (NH3 ) and methane (CH4 ) at ~ 1200°C over a Pt catalyst. Ammonia synthesis entails several complex, highly emitting processes. Plasma-assisted HCN synthesis directly from CH4 and nitrogen (N2 ) could be pivotal for on-demand HCN production. Here, we evaluate the potential of dielectric barrier discharge (DBD) N2 /CH4 plasma for decentralized catalyst-free selective HCN production. We demonstrate a single-step conversion of methane and nitrogen to HCN with a 72% yield at <300°C. HCN is favored at low CH4 concentrations with ethane (C2 H6 ) as the secondary product. We propose a first-principles microkinetic model with few electron impact reactions. The model accurately predicts primary product yields and elucidates that methyl radical (·CH3 ) is a common intermediate in HCN and C2 H6 synthesis. Compared to current industrial processes, N2 /CH4 DBD plasma can achieve minimal CO2 emissions.