Preparation Of 3DOM-m SiO₂-supportted Composite Metal Oxides Catalysts And Their Catalytic Performances For Diesel Soot Combustion

Compared with gasoline vehicles,diesel vehicles provide more energy,longer service life and higher safety,which make it well developed in medium and heavy vehicles?e.g.trucks,ships,buses,etc.?.However,the exhaust from combustion of diesel fuel contains substances that are harmful to human health and environment.Diesel exhaust includes soot particles,carbon and nitrogen oxide,hydrocarbons,polycyclic aromatic hydrocarbons and a small amount of heavy metal ions,etc.,among them,the pollution of soot particles is more serious.Therefore,the removal of soot particles is the main goal of diesel exhaust purification.Now,there are three purification methods for diesel exhaust,namely,improvement of fuel quality,improvement of diesel engine,and aftertreatment of diesel vehicle exhaust.Aftertreatment of diesel vehicle exhaust is more effective and safe.Therefore,it is an important task for researchers to develop high active soot catalysts to eliminate the pollutants from the exhaust of diesel vehicle.Due to diesel soot particles are generally large?typically>25 nm?in diameter,whereas conventional catalysts have pore sizes less than 10 nm,soot can only contact the outer surface of the catalyst for the catalytic combustion of diesel soot,resulting in lower utilization of the active site of the catalyst.Therefore,macroporous materials,especially the three-dimensional ordered macroporous materials,have been greatly developed.Three-dimensionally ordered macroporous materials have large pore size,uniform distribution and orderly arrangement of pores.Compared with other porous materials,the unique pore structure of the three-dimensional ordered macroporous materials facilitates the material to enter the pores from all directions and reduces the diffusion resistance of materials.But 3DOM materials also have their shortcomings,3DOM materials with large channels are not to sieve and catalyze small particulate matter,which will affect their catalytic effect on diesel exhaust system with large particulate matter?soot particles?and small particulate matter?NO?.Therefore,the three dimensional ordered macro-mesoporous?3DOM-m?catalysts have gradually attracted the attention of people.It can separate,adsorb and catalyze pollutants,making macroporous structure catalyze large particles and Mesoporous structure catalyze small particles,and its catalytic effect is obviously better than that of single macroporous catalyst.In this thesis,Several series oflow cost,highly active and stable catalysts,including three-dimensionally ordered macro-mesoporous?3DOM-m?structure SiO₂ and3DOM-m SiO₂-supported composite metal oxides,manganese cerium composite metal oxides catalysts with different raw material ratios were prepared.The best active catalyst was obtained from them by testing the activity of the catalyst.In this thesis,the main conclusions are as follows:?1?PMMA microspheres with uniform particle size and good monodispersity were prepared by simple soap-free emulsion polymerization.3DOM-m SiO₂ was prepared by colloidal crystal template?CCT?method with PMMA arrays as template and using PEO-PPO-PEO?P123?,tetraethyl orthosilicate?TEOS?as precursors.?2?The composite oxide catalysts of 3DOM-m SiO₂ supported iron,cobalt,aluminum,nickel,copper,zinc,cerium,lanthanum,lithium metals individually mixed with manganese were prepared by impregnation method,different composite metal oxide nanoparticles have different particle sizes,and the redox performance is different.3DOM-m SiO₂-supported composite metal oxides catalysts show different catalytic activities for diesel soot combustion.The best catalytic activities of as-prepared catalysts is MnCeO_x/3DOM-m SiO₂.?3?Based on experimental results of the previous experimental work,manganese cerium composite metal oxides with different raw material ratios were perpared by by impregnation method.The conclusion is that the amount of the load is 40%,and the catalyst with Ce/Mn=1 has the best catalytic activity.The stability was tested and the result was better.and the activity of the best catalyst for catalytic combustion of soot at different concentrations of NO and SO₂ was also investigated.At last,the activity is better when the concentration of NO is 2000 ppm and the concentration of SO₂ is 0ppm.