Mn-based bimetallic catalysts for porous media combustion of lean coal mine methane: Catalytic performance and heat transfer mechanism

• Mn-based bimetallic catalysts were loaded on Al 2 O 3 porous ceramics for CMM combustion. • Mn-Ni catalyst showed excellent redox ability and a stable surface oxygen structure. • Mn-Ni achieved 814 °C, 99.6 % conversion, and 2.8 ppm NOx at φ = 0.37 under lean fuel. • A Mars–van Krevelen mechanism was proposed based on Mn/Ni redox synergy. • A heat–reaction coupling mechanism with staged combustion zones was constructed. Coal mine methane (CMM), a major source of methane emissions, offers significant potential for energy recovery and emission reduction. In this study, a porous media catalytic combustion system was developed using Mn-based bimetallic catalysts (Mn-Ni, Mn-Co, Mn-Fe, Mn-Cu) supported on Al 2 O 3 foam ceramics. The catalysts were characterized by XRD, SEM, BET, XPS, H 2 -TPR and O 2 -TPD, and their combustion performance was evaluated during both the preheating stage and under lean-fuel conditions. Mn-Ni exhibited the best comprehensive performance, maintaining a stable surface oxygen structure and exhibiting strong oxygen cycling ability. It achieved the highest preheating temperature and efficiency, and under φ = 0.37, it reached a reaction zone temperature of 814 °C, with 99.6 % methane conversion and NOx emissions as low as 2.8 ppm. A Mars–van Krevelen (MvK) reaction pathway was proposed for Mn-Ni, where Mn 4+ /Mn 3+ and Ni 3+ /Ni 2+ redox pairs facilitated active oxygen cycling and electron transfer. A heat–reaction coupling mechanism featuring upstream preheating, central main reaction, and downstream supplementary combustion was also established, enhancing methane conversion and system stability. This work provides insights into catalytic combustion mechanisms and supports the efficient utilization of low-concentration CMM in porous media systems.