The Catalytic Activity Studies Of Soot Combustion Over Perovskite Catalysts

From 1892, Diesel engines widely used in various Power devices and vehicles because of its good drivability, economy and durability.Carbon particles and NOx are two major pollutants in diesel exhaust. NOx can damage the human respiratory tract and lungs with highly toxic. Soot particles easy to be inhaled lobectomy in the lungs, causing the lung tissue damage, Carbon particles of HC and sulfate on adsorption have very great harm to human body, especially the most of the polycyclic aromatic hydrocarbons in HC , may cause cancer. Although the study of diesel exhausts processing catalyst for years, but so far has not yet found the diesel catalyst which like three catalyst used as efficient for gasoline vehicles.So highly active catalyst to catalytic diesel emission of pollutants are urgent needed to find. Under loose contact,the ABO₃ perovskite type oxide catalysts were investigated for soot combustion.Three series catalysts of La_0.5K_0.5BO₃ (B = Cu, Mn, Co, Ni), La_1-xK_xNiMnO₆ and La_1-xK_xCo_0.5Mn_0.5O₃ were prepared by the auto-combustion method. This series of catalysts formed perovskite structure. In La_0.5K_0.5BO₃ catalysts, When B sites is Cu or Co , the catalyst have good activity for soot combustion.In La_2-xK_xNiMnO₆ catalysts , when x=0.4, The catalyst catalytic activity for soot combustion is best.Because the catalyst not only have the larger peak areas, but also their peak temprature are lower than the La_2-xK_xNiMnO₆ samples with small substitution amounts. It indicates that La_2-xK_xNiMnO₆ samples with larger substitution amounts not only have the larger concentration of surface oxygen species (O^2-and O^-), but also the mobility of their lattice oxygen is stronger.Through the TPO circulation experiment,It can be seen that La_1.6K_0.4NiMnO₆ catalyst stability for soot combustion is very good. In La_1-xK_xCo_0.5 Mn_0.5O₃ catalysts, when x > 0.2, there are some peaks which not belong to the perovskite structure. Through the TPO experiment, it can be obtained that the catalytic activity of La_0.6K_0.4Co_0.5Mn_0.5O₃ catalyst is the highest.A few precious metals Pt were loaded on La_1.6K_0.4NiMnO₆ and La_0.6K_0.4Co_0.5Mn_0.5O₃ catalysts, Through the TPO experiment, it can be obtained that the activity of after loaded catalyst for soot combustion does not improve, but some decline. This can attributing to the Cl- of chlorine platinum acid which easy to make catalyst lost their active.The catalysts of Ba_0.5Sr_0.5Co_0.5Fe_0.5O₃ were prepared by the auto-combustion method.The sample has formed perovskite structure under 800℃roasting with a little oxide impurities without conversion. Through the TPO experiment,the catalytic activity of catalyst for soot combustion is not good. The reason is in the sample structure including a few impurity, which affect catalytic activity of catalyst.The catalysts of La_1-xSr_xCo_1-yFeyO₃ were prepared by the auto-combustion method.When x=0.3 and y=0.2, The catalyst La_0.7Sr_0.3Co_0.8Fe_0.2O₃ has better catalytic activity for soot combustion compere to other samples. The catalysts of La_0.7Sr_0.3CoO₃ were prepared by adopt total precipitation and auto-combustion. Through the TPO experiments,the catalyst prepared by the auto-combustion catalytic activity for soot combustion is better than the catalyst prepared by adopt total precipitation. It may be due to the catalysts prepared by adopt total precipitation is collected and generate more impurities, which reduces the catalytic activity.