A kinetic study of nonthermal plasma pyrolysis of methane: Insights into hydrogen and carbon material production

• Methane pyrolysis using a gliding arc yields H 2 and valuable carbon materials. • A 0D chemical kinetics model was developed to elucidate the reaction mechanism. • The reaction pathways for carbon formation during this process were investigated. • The reaction between CH 4 and H significantly contributes to hydrogen production. • Electron-impact dissociation of C 2 H 2 greatly contributes to solid carbon formation. Nonthermal plasma-assisted methane pyrolysis has emerged as a promising approach for hydrogen production under mild conditions while simultaneously yielding valuable carbon materials. Herein, we develop a plasma chemical kinetic model to elucidate the underlying reaction mechanisms involved in methane pyrolysis to hydrogen and solid carbon within a gliding arc (GA) reactor. A zero-dimensional (0D) chemical kinetics model was developed to simulate the plasma chemistry during the GA-based methane pyrolysis process, incorporating reactions involving electrons, excited species, ions, and heavy species. The model accurately predicted methane conversion and product selectivity in agreement with the experimental data. A strong correlation between hydrogen production and methane conversion was observed, primarily driven by the reaction CH 4 + H → CH 3 + H 2, contributing 44.2% to hydrogen formation and 37.7% to methane depletion. Electron impact collisions with hydrocarbons play a secondary role, accounting for 31.1% of H 2 formation. This work provides a detailed investigation into the mechanism of solid carbon formation in GA-assisted methane pyrolysis. Most of the solid carbon originates from the electron impact dissociation of C 2 H 2 through reactions e + C 2 H 2 → e + C 2 + H 2 /2H and subsequent C 2 condensation. C 2 radicals are highlighted as the major contributors to solid carbon formation, accounting for 95.0% of the total carbon yield, which might be due to the relatively low C–H dissociation energy in C 2 H 2 . This kinetic study offers a comprehensive understanding of the mechanisms behind H 2 and solid carbon formation during GA-assisted methane pyrolysis.