Enhancing efficient combustion of low-concentration methane by introducing preheating into a porous media catalytic system

Methane is a potent greenhouse gas that poses a significant environmental challenge due to the large-scale release of low-concentration methane (LCM) during coal mining operations. However, the difficulty in achieving stable combustion of LCM hampers its efficient utilization. In this study, a MnO x /Al 2 O 3 porous media catalyst was synthesized using alumina foam ceramics as the support. The catalyst was characterized using FESEM-EDS, BET, XRD, and XPS. The effects of equivalence ratio, inlet velocity, and preheating temperature on combustion performance were systematically evaluated. The results demonstrated that increasing the preheating temperature significantly enhanced the catalytic performance of the MnO x /Al 2 O 3 catalyst during the combustion process. At a preheating temperature of 150 °C, combustion stability was significantly improved, the lean flammability limit of methane was reduced to 0.35, and the maximum methane conversion rate exceeded 95.0 %. However, increasing the preheating temperature intensified the non-uniformity of the temperature distribution within the burner, leading to increased emissions of CO and NOx. A dual-stage preheating mechanism based on the porous media structure was proposed to explain the enhanced combustion performance. A catalytic combustion mechanism of methane over MnO x /Al 2 O 3 was proposed, the Mn 4+ /Mn 3+ redox cycle was identified as a key factor in maintaining catalyst activity. These findings provide valuable insights into the development of efficient catalysts and the integration of preheating strategies for LCM combustion, contributing to the effective control and utilization of coal mine methane emissions. • A combined preheating–catalysis strategy was developed for LCM combustion. • Preheating at 150 °C reduced the lean flammability limit to 0.35. • Two-stage preheating and heat recirculation mechanism ensured efficient combustion. • MnO x /Al 2 O 3 catalyst demonstrated high activity and stability with low emissions. • Mn 4+ /Mn 3+ redox cycle sustained active oxygen replenishment and catalytic activity.