Transition metal modified Ce-based catalysts for low concentration methane combustion in porous media burners

Abstract

Coal mine methane is typically emitted at low concentration, making self-sustaining combustion for methane abatement challenging. Herein, Ce-based catalysts doped with Mn, Fe, and Co were supported on open-cell foams to couple dopant-regulated surface chemistry with porous-media heat recirculation for lean methane combustion. Combined characterization and DFT calculations revealed that transition-metal dopants regulated the CeO₂ surface chemistry by increasing Ce³⁺ concentration, promoting oxygen vacancy formation, and enhancing reactive oxygen mobility. Among the catalysts, the Co-doped sample exhibited the strongest redox promotion effect, extending the flammability limit to 0.38 and sustaining stable combustion at inlet velocities up to 0.127 m s⁻¹. More importantly, Ce–Co converted localized heat release into a broader and smoother axial temperature field with a moderated peak temperature of around 700 °C, thereby suppressing hotspots while maintaining high CH₄ conversion, CO below 900 ppm, and single-digit NO_x emissions. DFT calculations further revealed that dopant effects arise mainly from stabilizing dehydrogenated intermediates rather than strengthening molecular CH₄ adsorption. Co doping gave the highest work function and strongest stabilization, with an adsorption energy of −275.32 kJ mol⁻¹. These findings identify the synergy among oxygen mobility, intermediate stabilization, and porous-media heat feedback as the key to stable and low-emission lean methane combustion.