• Doping of Ca produces the lattice defects, and increases the high-valent Mn species. • 3DOM perovskite has an ideal multi-stage pore channel and a high specific surface area of 66.9 m 2 /g. • Unique structure increases oxygen vacancies and weaken the Mn-O bond strength. • Optimized structure enhances the adsorption, activation and mass transfer of O 2 and CH 4 . • Reaction rate of EG-3DOM La 0.8 Ca 0.2 MnO 3 is primarily affected by oxygen partial pressure. To effectively utilize the low-concentration methane during coal mining, a Ca-doped three-dimensional ordered macro-porous (3DOM) perovskite is synthesized via a sol–gel method using silica microsphere templates. The catalyst exhibits a high specific surface area with multi-stage pore channels. The modified EG-3DOM La 0.8 Ca 0.2 MnO 3 is shown to exhibit excellent activity (T 10 at 374.4 °C) in methane catalytic combustion. Ca doping significantly distorts the perovskite lattice, while Mn active sites and oxygen species concentration primarily determine catalytic activity. A-site metal doping enhances the synergistic effect between La and Mn, reducing particle size while increasing surface high-valent Mn species. The unique multi-stage pore structure exposes more active sites, facilitating CH 4 /O 2 adsorption and their mass transfer. Additionally, abundant surface oxygen vacancies are also important intermediates, which not only weaken Mn-O bonds but also stimulate the conversion of O ads into O lat . Finally, based on kinetic experiments, a one-step catalytic mechanism for ultra-lean methane combustion is proposed, clarifying the relationship between reactants and catalyst surface. This work provides a feasible way to enhance low-concentration methane combustion by applying perovskites.
Ni et al. (Fri,) studied this question.