Catalytic combustion of low-concentration methane over transition metal oxides supported on open cell foams

Methane is a potent greenhouse gas, and mitigating its substantial emissions, primarily from coal mines with low concentrations, is among the most effective strategies to slow global warming. Catalytic combustion using transition metal oxides is increasingly pivotal in addressing this issue; however, the low-temperature activity of these catalysts limits their widespread application. In this study, we aimed to develop highly active and costeffective catalysts for large-scale combustion of low-concentration methane. To this end, a series of transition metal oxides (Cr2O3, Mn2O3, Fe2O3, Co3O4, NiO, and CuO) supported on open cell foams were synthesized, and their catalytic performance for methane combustion at 1 vol% CH4 was assessed in a fixed-bed reactor. Comprehensive characterization was conducted using XRD, SEM-EDS, XPS, H2-TPR, and O2-TPD techniques to elucidate the underlying mechanisms of CH4 catalytic combustion. Results demonstrated that the structured catalysts exhibited exceptional activity and thermal stability. Among them, NiO showed the highest activity, followed by Fe2O3 and Co3O4 with similar activity, and then Mn2O3, CuO, and Cr2O3 showing progressively lower reactivities. Complete CH4 conversion was achieved over NiO at approximately 500 degrees C, comparable to certain noble metal catalysts. The superior catalytic activity was attributed to the abundant reactive oxygen species, originating from chemically adsorbed oxygen and surface lattice oxygen transformations. Additionally, the rich oxygen vacancies facilitated CH4 dissociation and enhanced activity. This study provides an effective framework for advancing catalyst design to improve methane oxidation efficiency, thereby enhancing the practical management and utilization of low-concentration methane emissions from coal mining activities.