采用水油两相双引发剂的无皂乳液聚合法制备了羧基改性的聚甲幕丙烯酸甲酯(PMMA)聚合物微球,并以此为模扳,采用胶体晶体模板法制备了三维有序大孔(3DOM)钙钛矿LaFeO_3催化剂.同时采用柠檬酸络合燃烧法制备了纳米钙钛矿LaFeO_3催化剂.通过傅里叶红外光谱、扫描电镜、X射线衍射和激光粒度仪等方法对样品进行了表征.采用程序升温氧化反应评价了催化剂对模拟柴油机炭黑颗粒催化燃烧的活性.结果表明,制备的羧基改性PMMA聚合物微球固含量约为10%,表面羧基含量约为3mmol/g.微球粒径分布均匀,且可通过调节反应条件得到不同的粒径,町控范围在300～700nm.所制得的3DOM钙钛矿LaFeO_3催化剂以六方有序的方式排列,其孔径及孔径收缩率分别为300nm和32%,大孔孔壁甲均厚度约50nm.该催化剂对炭黑颗粒催化燃烧的T_(10),T_(50),T_(90)和S~m_(CO2)分别为340,412,458℃和99.8%,件能优于纳米LaFeO_3催化剂.
Carboxy-modified polymethyl methacrylate (PMMA) microspheres were prepared using an emulsifier-free emulsion polymeriza-tion technique with water-oil biphase double initiators. Three-dimensionally ordered macroporous (3DOM) LaFeO_3 perovskite-type complex oxide was synthesized using a colloid crystal template, which was assembled by centrifugation of carboxy-modified PMMA spheres. The nanometric LaFeO_3 oxide as a reference sample was also prepared by the citric acid ligation method. The samples were characterized by the techniques of Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and a laser particle size analyzer. Their catalytic performance for diesel soot combustion was investigated by temperature-programmed oxidation reaction. The results indi-cated that the obtained carboxy-modified PMMA spheres had carboxyl groups on the surface and did not show any aggregation, and they were suitable for the preparation of colloidal crystals. Their contents of solids and carboxyl groups were 10% and 3 mmol/g, respectively. The particle size distribution of the microspheres was narrow and the microspheres with diameter of 300-700 nm can be designed and pre-pared under different process conditions. The obtained 3DOM LaFeO_3 catalyst had a hexagonally well-ordered array, and the diameter of macropore was about 300 nm, corresponding to a shrinkage ratio of 32%. The average thickness of its hole wall was about 50 nm. The T_(10), T_(50), T_(90), and S_(CO2)~m of 3DOM LaFeO_3 catalyst for soot combustion were 340, 412, 458 ℃ and 99.8%, respectively. Compared with the nano-LaFeO_3 catalyst for soot combustion, 3DOM LaFeO_3 catalyst has higher activity.
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