Efficient Direct Decomposition of NO over La_0.8A_0.2NiO₃ (A=K, Ba, Y) Catalysts under Microwave Irradiation

La_0.8A_0.2NiO₃ (A=K, Ba, Y) catalysts supported on the microwave-absorbing ceramic heating carrier were prepared by the sol-gel method. The crystalline phase and the catalytic activity of the La_0.8A_0.2NiO₃ catalysts were characterized by XRD and H₂ temperature-programmed reduction (TPR). The effects of reaction temperature, oxygen concentration, and gas flow rate on the direct decomposition of nitric oxide over the synthesized catalysts were studied under microwave irradiation (2.45 GHz). The XRD results indicated that the La_0.8A_0.2NiO₃ catalysts formed an ABO₃ perovskite structure, and the H₂-TPR results revealed that the relative reducibility of the catalysts increased in the order of La_0.8K_0.2NiO₃ > La_0.8Ba_0.2NiO₃ > La_0.8Y_0.2NiO₃. Under microwave irradiation, the highest NO conversion amounted to 98.9%, which was obtained with the La_0.8K_0.2NiO₃ catalyst at 400 °C. The oxygen concentration did not inhibit the NO decomposition on the La_0.8A_0.2NiO₃ catalysts, thus the N₂ selectivity exceeded 99.8% under excess oxygen at 550 °C. The NO conversion of the La_0.8A_0.2NiO₃ catalysts decreased linearly with the increase in the gas flow rate.