Catalytic performance of the Mn-Ce catalysts in lean methane combustion prepared by a redox co-precipitation method

A series of Mn-Ce catalysts with different Mn/Ce ratios were prepared by a redox co-precipitation method and characterized by N₂ sorption, XRD, XRF and XPS; their catalytic performance in lean methane combustion was investigated. The results indicate that the Mn/Ce ratio has a great influence on the activity of Mn-Ce catalyst in lean methane combustion. With an increase of the Mn/Ce ratio from 3:7 to 9:1, the activity of the Mn-Ce catalyst increases gradually and the reaction temperature needed for a methane conversion of 50% (t₅₀) decreases from 501 ℃ to 446 ℃; however, a further increase in the Mn/Ce ratio may lead to a decrease in the catalytic activity. The performance of Mn-Ce catalyst is related to many factors such as the surface area and the concentration of higher valence manganese (Mn⁴⁺) species, lower valence cerium (Ce³⁺) species and lattice oxygen; in particular, KMn₈O₁₆ is of benefit to enhancing the activity of Mn-Ce catalyst.