Surface Modification Of SBA-15 And The Development Of Mesoporous La_0.8Sr_0.2CoO₃ Perovskite-type Catalysts

La_0.8Sr_0.2CoO₃ perovskite type oxides exhibit high catalytic activity in CO oxidation,but the perovskite type oxides prepared by traditional methods has a low specific surface area(<50 m²·g^-1),which limits its wide application.The perovskite type oxide with mesoporous structure has the larger specific surface area,so it has more contactable catalytic activity site and improved the catalytic activity.However,it is still difficult to prepare perovskite-type oxides with good mesoporous structure and excellentlow-temperaturecatalytic activity.Based on this research problem,the surface modified SBA-15 is used to prepare La_0.8Sr_0.2CoO₃nano-oxides.Noble metal Pd for the doping and loading of mesoporous La_0.8Sr_0.2CoO₃to further improve its catalytic activity has been researched,the catalytic activity ofthe mesoporous La_0.8Sr_0.2CoO₃ type perovskite catalystsin CO oxidationwere researched and discussed.1.The mesoporous SBA-15 with large pore size was prepared by the dual template method by using P123 and F127 as the structural directing agent.The pore size of thesynthesized SBA-15was 10.1 nm,and the specific surface area was 802m²·g^-1.The surface of SBA-15 was modified by post-grafting method.Methyl and amino groups were grafted on the surface of mesoporous silica,and the mesoporous silica template with different surface properties was synthesized for the preparation of mesoporous La_0.8Sr_0.2CoO₃catalysts.The structure and properties of the hard template were characterized by SAXD,TEM,BET,FT-IR.2.In this paper,the mesoporous La_0.8Sr_0.2CoO₃ catalysts were prepared by sol-gel method combined with nano-casting route under different preparation conditions,which was applied to the catalytic oxidation of CO in automobile exhaust gas.The mesoporous La_0.8Sr_0.2CoO₃catalysts prepared at the calcination temperature of 650℃,n_{hard template}:n_catalyst=2:1 and pH=1 exhibited the highestCO catalytic oxidation activity.3.The effect of the surface properties of rigid template SBA-15 on the structure and properties of mesoporous La_0.8Sr_0.2CoO₃ oxides were systematically studied.The results show that the mesoporous La_0.8Sr_0.2CoO₃ oxide exhibits the best catalytic activity by using CH₃-SBA-15-OH/NH₂ template with methylation modified on the outer surface,hydroxylation and amino modification on the internal surface.Under the conditions of 2vol%CO,3vol%O₂ and Ar gas as the reaction gas composition and the space velocity of 20000 h^-1,the T_50%and T_90%of the catalystswere 120℃and 140℃,respectively.The presence of higher valenceof Co ions,increased the surface adsorption oxygen species content,lattice Sr enrichment in the surface aresignificantly contributed to the improved catalytic activity.4.The xPd/La_0.8Sr_0.2CoO₃catalystswere prepared by by equal volume impregnation method.Pd-doped La_0.8Sr_0.2Co_1-x-x Pd_xO₃ catalysts were prepared by sol-gel hard template method.The structure,morphology and properties of the mesoporous perovskite catalysts were characterized by XRD,TEM and H₂-TPR,et.al.The results show that Pd doped into perovskite lattice reduced the catalytic activity of La_0.8Sr_0.2CoO₃in CO oxidation.On the contrary,Pd in xPd/La_0.8Sr_0.2CoO₃was uniformly dispersed on the La_0.8Sr_0.2CoO₃ catalysts surfacein the forn of PdO and could significantly improve its catalytic activity,which is mainly due to the synergistic effect of precious metal Pd species and perovskite type oxides.