Plasma Catalytic Non-Oxidative Conversion of Methane into Hydrogen and Light Hydrocarbons

Abstract

Recently, direct non-oxidative conversion of methane (NOCM) into hydrogen and light hydrocarbons has garnered considerable attention. In our work, we employed a dielectric barrier discharge (DBD) plasma over a GaN/SBA15 catalyst for NOCM. Adding catalyst to plasma remarkably promotes the conversion of CH₄, resulting in a significant improvement, for instance, from 27.8 to 39.2%. A systematic investigation of plasma performance at different discharge powers with and without catalyst was conducted. In the case of plasma + 15wt% GaN/SBA15, CH₄ conversion reaches an impressive 79.4%. However, it exhibits the lowest selectivity of 14.4% for C₂+, while achieving the highest selectivity for hydrogen at 48.9%. Several characterization methods, including XRD, SEM, BET, XPS, and TPO-MS, were used to study the mechanism of the reaction. Plasma electrons and ions can effectively interact with activated CH3 radicals, promoting their adsorption onto Ga sites on the catalyst surface. Simultaneously, hydrogen atoms adsorb onto neighboring N atoms, rapidly delocalizing to produce H₂, and the delocalization of hydrogen atoms in C species leads to the formation of species like CxHy. This study highlights the potential of plasma catalysis in significantly improving CH₄ conversion at lower temperatures and atmospheric pressure.