Effect of highly dispersed Co₃O₄ on the catalytic performance of LaCoO₃ perovskite in the combustion of lean methane

In this work, a series of nano LaCoO₃ perovskite catalysts were effectively synthesized by a sol-gel method through modulating the La/Co molar ratio. These catalysts were characterized by ICP, XRD, N₂ sorption, H₂-TPR, O₂-TPD, and XPS, and their catalytic performance in the lean methane combustion were then investigated. The results indicate that highly dispersed Co₃O₄ nanoparticles on the LaCoO₃ perovskite catalysts are beneficial to the activation of CH₄ at a low temperature, while the La-Co-perovskite bulk phase can provide a large amount of lattice oxygen, which can enhance the reaction rate of methane combustion and the catalytic stability at a high temperature. Through altering the La/Co molar ratio, the dispersion of Co₃O₄ nanoparticles in the La-Co-perovskite catalyst can be effectively modulated, to achieve the concurrence of low-temperature activity and high-temperature stability in the lean methane combustion. In particular, the La_0.9CoO₃ perovskite catalyst with a La/Co molar ratio of 0.9 exhibits excellent performance in lean methane combustion, with a light-off temperature of 382 ℃ at a space velocity of 30000 mL/(g_cat·h), the light-off temperature of methane is 382 ℃, and the methane conversion rate is still maintained above 95% after 72 h of stable operation, indicating that the highly dispersed Co₃O₄ nanoparticles were beneficial to the low-temperature activation of CH₄, and the lanthanum-cobalt-perovskite bulk phase in the catalyst could provide a large amount of lattice oxygen, which promotes the catalytic combustion rate of CH₄ and the high-temperature stability of the catalyst under high-temperature conditions. By modulating the lanthanum-cobalt ratio, the dispersion state of Co₃O₄ nanoparticles in the catalyst can be effectively modulated, and then the effective unification of low-temperature activity and high-temperature stability of the catalyst can be achieved, which guides the future development of low-cost, high-activity and high-stability catalysts for methane catalytic combustion.