Study On La_0.8Ce_0.2Mn_1-xNi_xO₃ For Catalytic Combustion Of Diesel Soot

Using particle Oxidation Catalyst(POC) is one of important approaches to reduce particle matter(PM) from diesel engines. Focused on the POC, therefore, a series of La0.8Ce0.2Mn1-x Nix O3 perovskite-type catalysts were prepared by sol-gel method.The physical and chemical properties and catalytic activities of these catalysts were analyzed using several analytical techniques, such as XRD, SEM, BET, FT-IR, H2-TPR and O2-TPD. The specific surface areas(SSA), the amount of the surface adsorbed oxygen(?-O2) and low-temperature redox ability of La0.8Ce0.2Mn1-x Nix O3 is increased as compared with La Mn O3. Reaction activity of reducing soot was studied using DTG. Among these catalysts, La0.8Ce0.2Mn0.8Ni0.2O3 performs the best acitivity. Its special temperatures of T10?Tm?T90 are 230?417?459oC, respectively, and reaction activation energy is 92.4 k J/mol.Reaction pathway of reducing soot by NOX was studied using in situ DRIFTS and NSC. The reaction mechanism of removing soot and NOX simultaneously is as follows: When the temperature is below 200 oC, NOx is physically adsorbed to the surface of the catalyst; When the temperature is between 200 and 400 oC, the metal cations with strong oxdizability on the active site of the catalysts will oxidize NOX into nitrate or nitrite, and store them on the surface of the catalysts. When the temperature is above 400oC, however, the nitrate or nitrite is decomposed and then reacts with soot to generate NOX, N2 and CO2.A POC coated with La0.8Ce0.2Mn0.8Ni0.2O3(POC20), which exhibited the highest catalytic activitiy among these catalysts, was used to investigate the abatement of the exhaust PM from a diesel engine. During the testing cycle of ESC, the reduction in the exhaust PM from the diesel engine reaches 82.3% by use of POC20, in which 43.2% of PM is trapped and 39.1% of PM is completely oxidized. In the case of the engine speed of 2510 r/min and the engine load of 100%, the POC20 shows a 93.4% reduction in the exhaust PM. The measurements of particle size distribution show that the exhaust particles with big size are conversed into the ones with small size through the POC.