Characterization and Performance of Ca-Substituted La1-xCaxCoO3-δ Perovskite for Efficient Catalytic Oxidation of Toluene

Perovskite oxides with ABO(3) structure are promising heterogeneous catalysts. This work intends to modify the physicochemical properties and catalytic behaviors of perovskite-type oxides by A-site substitution. La1-xCaxCoO3-delta perovskite catalysts with various x = 0, 0.1, 0.3, 0.5 and 0.7 were prepared and the toluene oxidation performance was investigated. The results show that the calcium substitution increased the surface area, pore volume of the perovskite oxides and the crystal structure was transformed from rhombohedral to cubic symmetry after calcium substitution. Besides, it also changed the surface element composition, low-temperature reducibility and surface oxygen species amounts. 50% of calcium substitution in A-site (La0.5Ca0.5CoO3-delta) was thought to be the optimal content due to the best comprehensive physicochemical properties. The toluene oxidation test verified that the La0.5Ca0.5CoO3-delta presented the best catalytic performance with T-50% = 183 degrees C and T-90% = 218 degrees C. The catalytic process was related closely with the rapid transformation of Co2+/Co3+ and the consumption and regeneration of surface adsorbed oxygen. A mechanism of toluene oxidation over La1-xCaxCoO3-delta perovskite was proposed.