Preparation, structural and catalytic properties of B-site ordered perovskite-type oxides

钙钛矿型氧化物作为催化剂等功能材料是非常重要的化合物。然而，关于所谓的双钙钛矿和三钙钛矿具有有序排列的B位阳离子的报道很少。本研究系统地合成了B位有序的双钙钛矿和三钙钛矿，并对其结构进行了表征。合成了Ba-W、Sr-W和La-Ti基双钙钛矿，并采用Rietveld方法对它们的晶体结构进行了优化。研究了丙烷在高氧化性条件下（O_2/C_3H_8=19.5）的氧化反应。催化活性与B^<2+>阳离子密切相关。含3d过渡金属离子的双钙钛矿对C_3H_8的氧化反应表现出较高的活性，而含IIA和IIB的双钙钛矿对C_3H_8的氧化反应表现出较高的活性。 ...更多信息 UP金属阳离子活性差。在所研究的每个系列中，Co化合物的活性最高。催化活性与B^<2+>O生成热之间呈火山状关系，表明该反应是以氧化还原机理进行的。当使用BaCoO_3、WO_3及其混合物时，在900 ℃下，金属Co沉积在还原的BaCoO_3相上形成碳纤维。在1000 ℃时，由于金属Co的团聚，碳纤维的生成量减少，而在1000 ℃时，双钙钛矿Ba_2CoWO_6上生成的碳纤维的形貌及其温度依赖性与其它样品不同，这可能是由于双钙钛矿结构的形成和Co.La_2ZnTiO_2的高分散性提高了合金的抗还原能力。6的光催化性能（甲醇分解）进行了评价。La_2ZnTiO_6催化剂选择性地生成CO，与TiO_2催化剂选择性地生成H_2形成鲜明对比。少

Perovskite-type oxides are very important compounds as functional materials such as catalysts. However, there are few reports on so-called double and triple perovskites which have ordered arrangement of B-site cations. In this study, systematic synthesis and structural characterization of B-site-ordered double and triple perovskites were carried out. Their catalytic activity was investigated in relation to the ordered structure.Ba-W, Sr-W and La-Ti based double perovskites were synthesized and their crystal structures were refined by Rietveld method. Accordingly, B-site ordered and disordered structures were able to evaluate successfully.The oxidation of propane in highly oxidizing condition (O_2/C_3H_8=19.5) was investigated over systematic series of double perovskites. The catalytic activity depended significantly on the B^<2+> cations. The double perovskites containing 3d transition metal ions showed high activity for C_3H_8 oxidation reaction, while those containing IIA and IIB gro … More up metal cations were poor in activity. The Co-compounds were most active in every series investigated. The relation between the catalytic activity and the heat of B^<2+>O formation displayed volcano-shaped dependence, strongly suggesting that the reaction proceeds by the redox mechanism.Ba-Co-W based oxides were applied to the reaction of carbon fiber formation. When BaCoO_3, WO_3 and the mixture of them were used, carbon fiber formation was confirmed on metal Co deposited on the reduced BaCoO_3 phase at 900 ℃. In the case of 1000 ℃, the amount of carbon fiber formation decreased due to agglomeration of metallic Co. On the other hand, morphology and its temperature dependency of carbon fiber formed on double perovskite Ba_2CoWO_6 was different from those on other samples at 1000 ℃, probably due to the improvement of reduction tolerance by the formation of double perovskite and the higher dispersion of metallic Co.La_2ZnTiO_6 was prepared and its photocatalytic properties (methanol decomposition) were evaluated. Carbon monoxide was selectively produced with La_2ZnTiO_6, which was in quite contrast to selective production of H_2 over TiO_2. Less