Preparation And The Catalytic Performances Of Macroporous Fe-based Metallic Oxides On The Simultaneous Removal Of Diesel Soot And NO_x

Diesel soot particles and NO_x?NO,N₂O and NO₂,etc.?emitted from diesel engine exhaust are the main sources of urban air pollution.A direct impact is on human living environment and human health.Catalytic purification of after-treatment technology is currently the most effective way to reduce diesel exhaust emissions,and research and development of highly active catalyst has been a focus.Therefore,it is significant to study the preparation of high activity catalyst for eliminating the soot particles and NO_x.It is also very important to study the reaction mechanism of soot combustion and NO_x reduction on the catalyst.In this thesis,the catalysts were prepared by using colloidal crystal template method to synthesize 3DOM Cu-Fe and Fe-Mn based metal oxide catalysts and the catalysts characterized by XRD,BET,SEM,TEM,XPS,H₂-TPR,Raman,FT-IR,etc.The catalysts activity of the catalysts was evaluated by the programmed temperature oxidation redox reaction,and the catalyst with highly catalytic performance was obtained.In the Cu-Fe metal oxide catalysts,Cu₂Fe₁O_x has the best catalytic effect.The catalytic T_m temperature is 453?,the window temperature of NO_x conversion is328-476?,and the maximum conversion rate of NO_x is 95.3%.In the Fe-Mn metal oxide catalysts,the best activity for eliminating soot and NO_x is the Fe₁Mn₃O_x catalyst.The T_m temperature of the soot combustion is 435?and for the NO_x reduction,the NO_x 80%conversion of the window interval 302-485?,and NO_x maximum reduction conversion rate is 96%.Fe₁Mn₃O_x catalyst NO_x window temperature widens 25?,and the maximum conversion rate increases by 0.7%,while the soot particles to reduce the combustion T_m temperature 18?,indicating that the catalyst redox performance is improved.Finally,the reaction mechanism of selective catalytic reduction of Fe₁Mn₃O_x and Cu₃Fe₁O_x catalyst was investigated by in-situ infrared analysis.At 300?,Fe₁Mn₃O_x catalyst,1247 cm^-1 belongs to NH₃ molecular complex adsorption in the L acid N-H vibration peak,and at 1431,1573 cm^-11 are assigned to the nitroso,chelated bidentate nitrate,and 1278 cm^-1 is due to bridged bidentate nitrates and 1341 cm^-1 is attributed to intermediate cis-N₂O₂-.At 500?,the 1281 cm^-1 is due to bridging bidentate nitrate peak and it becomes higher.The nitrate is formed to cover the active site,resulting in the non-selective oxidation of NH₃ at high temperature.It results in the deterioration of its high temperature activity.