The La <sub> 0.8 </ Sub> K <sub> 0.2 </ Sub> Of Mno <sub> 3 </ Sub> Preparation Conditions And The Impact Of Their Performance Evaluation

According to the domestic and foreign catalyst research of simultaneously removing the carbon particulates and the nitrogen oxide compound,discharged by diesel cars.This paper uses the combustion synthesis to prepare a series of La_1-xK_xMnO(X=0,0.1,0.2,0.3, 0.4)compound perovskite catalyst.The structure and characteristic of the La_1-xK_xMnO₃ compound perovskite catalyst was investigated by BET,TG-DTA,XRD,TPO.From the BET analysis,when La_0.8K_0.2MnO₃ catalyst in the time citric acid:nitrate=1:1,accumulates the maximal specific surface,gas and solid heterogeneity response has the highest speed and is the best activity for the carbon black catalytic combustion.From the XRD spectrogram that,the LaMnO₃ catalyst characteristic diffraction peak conforms to the perovskite structure.The series of La_1-xK_xMnO₃ catalyst basically appeared the same characteristic diffraction peak that of the crystal perovskite.When the quantity of K-substituted X＜0.2,it does not change the crystal structure of LaMnO₃ perovskite.However,when X＞0.3,the crystal structure begins to change.The catalytic activity test result indicated that,the carbon particulates combustions without any catalyst,not only produces massive CO₂,but the burning temperature generally all above 550℃and the maximum weightlessness temperature achieve 600℃.However, with the series of La_1-xK_xMnO₃(X=0,0.1,0.2,0.3,0.4)catalyst,the carbon particulates burning temperature and the peak value temperature have both migrated to the low temperature area.Thereinto,the La_0.6K_0.4MnO₃ is the most active catalyst for the carbon particulates combustion,the burning temperature and the peak value temperature are separately reduced 144℃and 151℃.The reason is that,during the process K partially substitute for the La,Mn ions transform from Mn³⁺to Mn⁴⁺.Along with the increasing K-substituted quantity,the Mn⁴⁺ions also increase and possibly has produced the oxygen vacancy.Owe to the Mn⁴⁺ions and the oxygen vacancy,the La_1-xK_xMnO₃ catalyst oxidized ability is greatly enhanced,and the carbon particulates burning temperature is further reduced.Moreover,the TPO test result indicated that the catalytic combustion under an NO flow, can reduce the carbon black burning temperature.In other words,the nitrogen oxides can promote the catalytic combustion of the carbon particulates.