Study On Synthesis Of Porous Perovskite Catalyst And The Catalytic Properties For Removal Of Diesel Exhaust

Rare-earth perovskite-type oxides play an important role in diesel exhaust removal. In this thesis, a biomorphic La_0.9K_0.1CoO₃ catalysts have been fabricated using natural pine blocks as the template and hierarchical pore structure SiOC ceramic matrix loading La_0.9K_0.1CoO₃ catalysts have been prepared using polystyrene microspheres （PS） modified La_0.9K_0.1CoO₃ powders (PS@La_0.9K_0.1CoO₃) as the template through a preceramic polymer conversion process. The physic-chemical properties of these catalysts are characterized by N2 adsorption-desorption isotherms, XRD, FT-IR, SEM, TEM, EDX, and TG-DSC. The catalytic activity of the porous La_0.9K_0.1CoO₃ catalysts for NO_x and HC removal are studied in an axial fixed bed reactor under the simulated diesel exhaust conditions. And the catalytic properties for soot combustion are carried out on a temperature-programmed system.As to the biomorphic La_0.9K_0.1CoO₃ catalysts, natural pine blocks were impregnated into the sol containing La, K and Co with the uploading of 84 %. IR and XRD result show that these dipped samples could be subsequently possessed ABO₃ perovskite structure via carefully pyrolysis in flowing argon at 800°C, and then converted into well crystallization of La_0.9K_0.1CoO₃ after calcinations in air at 800°C. The SEM and TEM results revealed that the La_0.9K_0.1CoO₃ catalyst had porous structure with integrate channel and uniform hole. The average diameter and the wall thickness were concentrated in 15 40μm and 2 8μm, respectively. It has large surface area （147.97 m2/g）, higher than corresponding powder or fiber morphology. In tight-contact with carbon black condition, the ignition temperature （Ti） and 50 % conversion temperature of soot （T50） decrease to 313°C and 454°C, respectively. Furthermore, the porous La_0.9K_0.1CoO₃ catalysts exhibited excellent catalytic activity of 82.2 % for NO_x removal. What’s more, the C3H8 started activation at 320°C and completed conversion at approximately 485°C under the porous La_0.9K_0.1CoO₃ catalysts existence.The hierarchical pore structure SiOC ceramic matrix were obtained using homemade polystyrene microspheres （PS） as pore agent, via two-step crosslink process and pyrolysis using PHMS + D4Vi liquid as precursors in flowing argon at 1000°C. The SiOC ceramics had big apparent porosity of 77.1 % when the mass ratio of PHMS/D4Vi = 1.0 and Pt/（PHMS + D4Vi） = 1.0. In addition, the La_0.9K_0.1CoO₃ powders prepared from sol-gel process were modified by microemulsion method to PS@La_0.9K_0.1CoO₃. And using PS@La_0.9K_0.1CoO₃ as the template, hierarchical pore structure SiOC ceramic matrix loading La_0.9K_0.1CoO₃ catalysts were successfully synthesized in-situ. As a result, the SiOC/La_0.9K_0.1CoO₃ composites had relatively highest ceramic yield of 80 %, and the apparent porosity was 69.3 %, the amount of La_0.9K_0.1CoO₃ was 15.09 %. The studies need to be further investigated.The research results will be offered as basic theoretic supports for automobiles and engines in our country to meet with the more strict emission regulations.