A kinetic model for Pd-based hydrogenation of acetylene-rich streams typical of post-plasma applications

The advancement of electrified chemical processes prompts interest in novel technologies such as plasma-based methane (CH₄) conversion into high-demand chemicals. Specifically, nanosecond-pulsed discharges (NPDs) coupled with downstream Pd-based catalysts have demonstrated the best performance in a two-step, integrated process for converting CH₄ into ethylene (C₂H₄). Given the untested composition range involved in this application, the focus of this work is the isolated performance of Pd-based catalysts in typical post-plasma conditions. Extensive campaigns of experiments are run in both traditional and novel stream compositions. The differences with traditional tail-end olefin-rich hydrogenation are highlighted, and a hybrid steady-state kinetic model is proposed, combining the traditional Langmuir-Hinshelwood-Hougen-Watson (LHHW) approach with an improved reversible adsorption methodology. The ability to accurately predict C₂H₂ hydrogenation kinetics with C₂H₂-rich and C₂H₄-poor streams is achieved by the new model, contrary to existing conventional models. Preliminary insights into catalyst optimization for scalable plasma-to-olefin routes are presented.