Synthesis Of Spinel-type Re_xCo_1-xMn₂O₄（Re=Ce/La） Catalysts And Research Of Catalytic Performance For NO_x-assisted Soot Combustion

With the development of society,diesel engines,especially marine diesel engines and heavy duty diesel engines,release plenty of NOx and soot particles that have a great and negative impact on the environment.The simultaneous removal of NOx and soot particles by catalytic combustion allowed the DPF to be passively regenerated,and has a very important research significance in the development of diesel engine tail gas treatment technology.Spinel oxides have been reported as effective for the simultaneous removal of NOxand soot.This thesis tried to prepare several spinel oxides with different micro-morphology by using a solvent thermal method and/or a template method.The as-prepared catalysts were characterized by XRD,Raman spectra,H2-TPR,SEM,XPS and thermogravimetric analysis.The catalytic activities of all the catalysts were tested in soot combustion reaction.The Ce-Cocomposite nanofibers prepared by a solvothermal method have a length of 800 nm and a diameter of about 35-40 nm.The Ce-Co composite with Ce/Co = 0.5 showed a best catalytic performance of T50 =427℃ in a loose contact condition.The doped spinel nanosized flowers were prepared by another solvothermal method with isopropanol and 1,3-propanediol as cosolvant.The diameter was about 400 nm and the folds were about 100 nm.The doped coball-manganese spinels were prepared at different temperatures and different times.The optimized conditions for the preparation of nanoflowers are:reaction at 190℃ for 36 h.The optimal catalyst was La0.5Co0.5Mn2O4 with a T50 = 520 ℃ under loose contact condition.The doped cobalt-manganese spinel catalyst with three-dimensional ordered macroporous structure prepared by PMMA hard template method.The ordered macroporous structure catalyst shows a macroporous pore size of about 200 nm,window pore size of about 40 nm and bridge thickness of about 20 nm.The reaction time and concentration of PMMA microspheres were explored and optimized for the development of the template method for the preparation of the doped cobalt-manganese spinel catalyst with three-dimensional ordered macroporous structure.The impact of different doping amount on the catalytic performance were studied In the loose contact mode,the Ce0.9Co0.1Mn2O4andLa0.3Co0.7Mn2O4 showed the best catalytic performance when the TPO reaction was used as the activity evaluation standard.The Tm(Ce0.9Co0.1Mn2O4)≈Tm(La0.3Co0.7Mn2O4)≈377 ℃...