Partial Substitution Of La₂CuO₄ At A?B Sites For Simultaneous Removal Of NO_x And Soot

With the wide application of diesel engines,the pollution caused by exhaust emissions has become a global problem,which makes the exhaust treatment problem become very urgent.Therefore,the research of diesel engine exhaust purification technology is of great significance.Nitrogen oxides?NO_x?and particulate matter?PM?,the main pollutants in diesel exhaust,are the main culprits of acid rain,photochemical smog and haze.Due to the trade-off effect of the them,the in-machine purification technology cannot meet the emission requirements and requires post-processing technology.The catalytic treatment technology which can simultaneously remove NO_x and soot is undoubtedly the most attractive.Perovskite catalysts have attracted much attention because of their unique structure.In this paper,a series of perovskite catalysts were synthesized by citric acid sol-gel method.The characterization of X-ray diffraction?XRD?,Fourier transform infrared spectroscopy?FT-IR?,and activity evaluation were used to study the performance of the catalyst for simultaneous removal of NO_x and soot.LaMnO₃,La₂NiO₄ and La₂CuO₄ catalysts were synthesized.The structures of perovskite and perovskite-like catalysts and the effects of different B-site elements on the catalytic performance were studied.La₂CuO₄ catalyst has higher NO_x conversion and stronger oxidation capacity than LaMnO₃ and La₂NiO₄ catalysts.Therefore,La₂CuO₄ catalyst was selected for further study.A series of La_2-xBa_xCuO₄ catalysts were prepared by partial substitution of Ba²⁺for La³⁺,and the effects of Ba²⁺substitution on the catalytic performance were investigated.It was found that the successful doping of Ba²⁺into perovskite-like lattice resulted in the transformation of crystal structure from orthorhombic?Bmab?to tetragonal?F4/mmm?,and a large number of oxygen vacancies and Cu³⁺were generated in the system.The activity of the catalyst was significantly improved,the La_1.8Ba_0.2CuO₄ catalyst exhibited the best simultaneous removal efficiency.The initial combustion temperature T_i was 361?,the maximum combustion temperature T_m was 511? of soot,and NO conversion reached 81.4%.A series of La₂Cu_1-yCo_yO₄ catalysts were synthesized by using Co as B-site substituting element,and the effects of different Co substituting amount on the catalytic performance were studied.It was found that with the introduction of Co²⁺,a large amount of interstitial oxygen was produced in the catalyst system,the mobility of oxygen was enhanced,and the activity of catalyst was increased.La₂Cu_0.8Co_0.2O₄ catalyst had the best simultaneous removal efficiency.The initial combustion temperature T_i was 385?,the maximum combustion temperature T_m was 621? of soot,respectively,and NO conversion reached 97.9%.