Plasma-Assisted Catalytic Oxidation of Methane: Modelling and Kinetic Insights

Global warming caused by greenhouse gases is becoming increasingly severe each year. Catalysts have been employed to reduce emissions from internal combustion engines, but thermal catalytic decomposition is limited by the need for high-temperature operation and the catalyst deactivation. To overcome these limitations, plasma and plasma–catalyst hybrid systems have emerged as alternatives. Although many studies have examined the effects of gas composition, catalyst type, and temperature on greenhouse gas conversion through experimental, theoretical, and numerical approaches, few have investigated the physical mechanisms underlying plasma–catalyst synergy.

In this study, CH₄ and CO₂ conversion (30–300 °C) was investigated using a surface dielectric barrier discharge (sDBD) reactor with a Pd/Al₂O₃ catalyst. CH₄ conversion was highest with plasma alone, while CO₂ conversion increased only under plasma–catalyst hybrid conditions. A 0D global model incorporating electron impact reactions, gas-phase chemistry, and surface reactions based on Mars–van Krevelen kinetics was utilized. CH₄ conversion was driven mainly by plasma-generated radicals, rather than direct electron impact dissociation. Catalytic oxidation via lattice oxygen enhanced conversion, but incorporation of O radicals into Pd oxygen vacancies reduced gas-phase reactivity. Temperature-dependent trends in radical formation and catalytic behavior provide insights into optimizing plasma–catalyst hybrid systems.