Effects of Preparation Methods on the Catalytic Performance of LaMn0.8Mg0.2O3 Perovskite for Methane Combustion

A perovskite-type composite oxide, LaMn0.8Mg0.2O3, was prepared by five methods, i.e., glycine-nitrate, sol-gel, co-precipitation, combustion synthesis, and hydrothermal treatment. The composites were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, H2-temperature-programmed reduction, and N2 adsorption-desorption isotherms. The catalytic activity of LaMn0.8Mg0.2O3 toward methane combustion was evaluated. The results show that the different preparation methods and calcination temperatures greatly influence the textural structure, crystallite size, and different oxygen species within the LaMn0.8Mg0.2O3 perovskite material. The perovskite catalyst synthesized by the glycine-nitrate method and calcined at 700 °C shows the best activity for methane combustion among the tested materials. Its T50 (the reaction temperature at which 50% CH4 is converted) is only ∼440 °C. This good catalyst performance can be attributed to the small crystallite size (12.4 nm), larger surface area (18.6 m2/g), and high concentration of surface Mn4+ cations, which creates more flexible and reactive surface oxygen species.