Structural and Catalytic Properties of Co-doped Perovskite Oxide on Coal Combustion

Abstract

In this paper, the structural and catalytic properties of co-doped perovskite oxide La_0.8Ce_0.2Mn_1−xCo_xO₃ are investigated. First, coal combustion catalysts of mesoporous perovskite-type La_0.8Ce_0.2Mn_1−xCo_xO₃ were prepared by using sol–gel method. The resulting powder was characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller’s test (BET), and thermogravimetric analysis (TGA). Then, the results showed that after partially substituting La with Ce and substituting Mn with Co in LaMnO₃, Ce occupied parts of the La site and Co occupied parts of the Mn site. As the substitution rate of Co increased, the pore diameter significantly decreased, and the specific surface area increased first and then decreased. Thirdly, thermogravimetric measurements and coal combustion constructed single-reaction model in the presence of the La_0.8Ce_0.2Mn_1−xCo_xO₃ catalysis indicated that the presence of catalysts reduced the reaction initiation temperature (T_eo), the maximum mass loss velocity temperature (T_max), and the completion temperature of the main pyrolysis (T_f). The addition of 5 % La_0.8Ce_0.2Mn_0.9Co_0.1O₃ to coal caused the reaction initiation temperature (T_eo) to decrease by 34 °C compared with coal alone. Lastly, a distributed activation energy model of 5 % La_0.8Ce_0.2Mn_0.9Co_0.1O₃ obtained an activation energy distribution curve. Results indicated that the activation energy of samples at the primary pyrolysis stage did not present a single peak value but mainly accumulated at 140–160 kJ, which could replace the mean activation energy of pyrolysis reaction. At the same time, frequency factor was not constant but presented a certain degree of linear correlation with activation energy, thereby indicating the presence of more than a single-reaction pyrolysis mechanism.