Experimental study on reduction of NO by CH₄ over La_0.8Sr_0.2MnO₃/α-Al₂O₃ in excess of O₂

Selective catalytic reduction of NO is necessary for the environment but the present adopted NH₃-SCR has its weaknesses. This paper proposes CH₄-SCR of NO with perovskite catalyst (La_0.8Sr_0.2MnO₃/α-Al₂O₃) and experiments were done to study the effect of key factors (resident time, temperature and the initial O₂ concentration). XRD patterns and SEM image show that La_0.8Sr_0.2MnO₃ is a catalyst with perovskite structure and this kind of structure has been proved to be efficient in SCR. Experiments show that CH₄ can convert NO efficiently in association with catalyst La_0.8Sr_0.2MnO₃/α-Al₂O₃ and the max NO conversion ratio is over 90%. The longer the resident time is, the higher the conversion of NO is. The conversion of NO increased with the increase of temperature when the initial concentration of O₂ ranged from 0% to 3% and moderate O₂ at high temperatures can promote the reduction of NO by filling oxygen vacancies in lattice and taking part in the reactions. The new catalyst La_0.8Sr_0.2MnO₃/α-Al₂O₃ could work efficiently in the widest range of oxygen concentration at 800 °C and it reached 90% with the oxygen concentration ranging from 4% to 6%. This research will provide further data to improve the process of SCR in the power plant.