Preparation Of Lanthanum Cobalt Perovskite Catalysts And Their Catalytic Performance For Methane Combustion

Methane catalytic combustion is a kind of energy utilization and exhaust gas treatment technology with high efficiency and low pollution. And the light-off temperature and peak temperature of CH4 combustion can be reduced significantly with catalyst. In this paper, the La0.6Sr0.4Co0.2Fe0.8O3-& perovskite catalysts were prepared, and low temperature N2 physical adsorption, X-ray diffraction (XRD),hydrogen temperature programmed reduction (H2-TPR), oxygen temperature programmed desorption (O2-TPD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the physical and chemical properties of the catalysts, and the catalytic combustion activity of low concentration of methane was investigated.La0.6Sr0.4Co0.2Fe0.8O3-& perovskite catalysts were prepared by co-precipitation method, micro-emulsion method, and citric acid complexing method. And the chemical and physical properties of these catalysts were studied. And the results show that the properties of the catalyst by citric acid complex method is the best.Influences of citric acid/metal ions molar ratio (CMMR) upon the physic-chemical properties and catalytic performances for methane combustion were investigated. The results indicated that CMMR affected the perovskite phase formation. Perovskite with a CMMR of 1.25 gave the best catalytic performance.When CMMR was 1.25, the formation of perovskite structure with less impurity,lower reduction temperatures for Fe4+ and Co3+, the ratio between adsorbed oxygen species and lattice oxygen was the highest , adsorbed oxygen more easily, and forming active species.The calcination atmosphere can affect the catalyst performance significantly. The catalytic activity sequence of these catalysts is Air>N2+air>N2. The catalyst calcined in air exhibits the best activity because of its best crystal and best dispersion.When calcination temperature is below 700 ℃,perovskite cannot be formed completely, and when the temperature is higher than 700 ℃, the catalyst is sintering and aggregated,the particle size is grown up. Single crystal La0.6Sr0.4Co0.2Fe0.8O3-δperovskite catalyst can be formed when the calcination temperature is 700 ℃, and exhibits the best catalyst activity.Barium doped La0.6Sr0.4Co0.2Fe0.8O3-δ perovskite catalyst is prepared with citric acid complexing method. Ba doping amount has little effect on catalyst surface, but it will affect the B4+ content and surface adsorption oxygen concentration, which have important influence on catalytic activity. When the doping amount of Ba is 0.1, the catalytic activity is the best.