| La1-xSrxMn03+σmixed oxides have good automobile exhaust catalytic properties. However, the research has been done shows that the catalyst has a smaller surface area, which restricts the function of the catalyst. Mesoporous of materials is an effective way to increase the specific surface area of catalyst, but it is a certain difficulty to achieve mesoporous structure of these series materials. In this paper, mesoporous La1-xSrxMnO3+σperovskite-type catalyst samples were sythesized by the hard-template wet impregnation sol-gel method. The preparation of citric acid as complexing agent, a variety of nitrate be used as inorganic sources, SBA-15 mesoporous silica be used as hard template.And it combines the advantage of sol-gel method prepared the Perovskite catalyst for automotive exhaust and hard template method prepared mesoporous materials(high surface area, narrow pore size). The prepared catalyst samples were characterized by XRD, SEM, AFM, FTIR and BET, and other test methods. XRD results showed that the samples obtained at a heating rate 5℃/min rising to 750℃keeping 2 hours appears the most pure, the higher crystallinity and smaller particle size. After removing the template, the Perovskite catalyst were characterized by BET, which shows the sample's high Surface area (143.7m2/g) that traditional methods can't reach, while samples also have better pore size distribution (most probable pore about 2.5nm) and larger pore volume (0.26cc/g). Among them, the template content on the specific surface area plays a decisive role.When the amount of template were 0,1:1,2:1, and 4:1, respectively the surface area were 10m2/g,70m2/g,100.9m2/g and 143.7m2/g. AFM analysis of samples shows that the catalyst particle size is about 18nm. BET and BJH results of the catalyst samples revealed the existence of a wide pore size distribution, the large hole about 10nm caused by the accumulation of nanoparticles, while the hole about 2.5nm Produce in the process of removing the template generated. According to its small-angle X-ray diffraction showed that samples prepared by hard template is the disorder mesoporous Structure.XPS and temperature programmed reaction(TPR) results showed that:when the catalyst prepared by hard template material, the increasing of the specific surface area of the samples improve the chemical adsorption oxygen content of the samples surface. Compared to the sample synthesized by traditional sol-gel method, their Oads/Olat value increased to 2.35 from 0.58, which Mn4+ content increased with the amount of template increased.The mesoporous structure of samples prepared by hard template is conducive to the spread of materials and catalytic reaction. Performance on the catalytic activity to CO:increasing the amount of template greatly enhanced its catalytic oxidation of CO. However, excessive use template, the catalytic activity have no more increase, but declined.CO oxidation results showed that:the order of A-bit doped La1-xSrxMnO3+σ/2SBA-15 series of samples for CO oxidation activity is La0.8Sr0.2MnO3+σ/2SB A-15>La0.7Sr0.3MnO3+σ/2SBA-15>La0.9Sr0.1MnO3+σ/2SBA-15> LaMnO3+σ/2SBA-15. This is consistent with the results of previous studies, so, hard-template method is reasonable to prepare mesoporous perovskite catalyst. Meanwhile, a seires of A/B-bit dual-doped samples La0.8Sr0.2Mn1-yCuyO3+σ/2SBA-15 (y=0,0.1,0.2,0.3) can improve the catalytic activity of CO with Cu content increased. And when y=0.2, the effect shows best. |
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