DBD plasma combined with Ni–Mn/SiO2 catalysts modified by myristic acid for methane oxidation in presence of water vapor

Abstract

Plasma catalysis is recognized as a promising technology for the elimination of methane. However, co-existence of moisture in flue gas reduces significantly the adsorption capacity of catalysts toward CH₄. Herein, Ni–Mn/SiO₂ catalysts were tuned by controlling the Ni/Mn molar ratio and subjected to hydrophobic treatment using myristic acid to promote methane oxidation under humid conditions. The plasma–catalytic system demonstrated a substantial improvement in CH₄ conversion and CO₂ selectivity compared to the plasma-only system owing to the synergistic effects of plasma and catalysis on methane degradation. The increase in the Mn/Ni molar ratio promotes the formation of Mn⁴⁺ on the catalyst surface and increases the specific surface area, facilitating the migration and adsorption of reactive oxygen species, which further improves the catalytic activity of methane oxidation reaction. In the presence of 5% water vapor, Ni–Mn(1 : 1)/SiO₂–MA exhibited the highest CH₄ conversion of 93.5% at 40 W. Due to the introduction of myristic acid with non-polar alkyl groups, a highly hydrophobic surface was obtained on modified catalysts, preventing the coverage of the active sites and promoting CH₄ adsorption. This study provides a new and viable solution to improve the performance of catalysts in methane oxidation under high-humidity conditions.