一步水热合成Y-Co3O4复合氧化物催化剂及催化分解N2O

用一步水热、分步水热、浸渍等方法分别制备Y-Co₃O₄复合氧化物，用于催化分解N₂O的反应，其中，一步水热法制备的催化剂活性较高。再用一步水热法制备了不同Y/Co物质的量比的Y-Co₃O₄复合氧化物，在优化出的催化剂（0.03Y-Co₃O₄）表面浸渍K₂CO₃溶液，制备K改性催化剂（0.02K/0.03Y-Co₃O₄）。用X射线衍射（XRD）、N₂物理吸附、H₂程序升温还原（H₂-TPR）、O₂程序升温脱附（O₂-TPD）、扫描电镜（SEM）、X射线光电子谱（XPS）等技术表征催化剂结构。研究发现，Co₃O₄和Y-Co₃O₄同为尖晶石结构，但Y-Co₃O₄的催化活性显著高于Co₃O₄。K改性增加了催化剂表面的活性位（Co²⁺），还有利于吸附氧的脱除，从而提高了催化剂活性。在无氧无水、有氧无水、有氧有水气氛中，K改性催化剂上的N₂O全分解温度分别为325、350、375 ℃，催化剂活性较高。有氧有水气氛350 ℃连续反应50 h，K改性催化剂上N₂O分解率保持90%以上，稳定性较高。研究发现，Y-Co₃O₄及K改性催化剂上N₂O分解反应的E_a和lnA之间存在动力学补偿效应。

Catalytic decomposition of N2O over Y-Co3O4 composite oxides prepared by one-step hydrothermal method

Y-Co₃O₄ catalysts with Y/Co molar ratio of 0.03 were prepared by several methods, such as one-step hydrothermal, two-step hydrothermal, and impregnation methods, to catalyze the decomposition of N₂O. Among these catalysts, the one prepared by one-step hydrothermal method exhibited the highest activity, and then the Y-Co₃O₄ catalysts with various molar ratios of Y/Co were synthesized by one-step hydrothermal method. Subsequently, the optimized 0.03Y-Co₃O₄ was impregnated by K₂CO₃ solution to prepare K-modified catalyst and named as 0.02K/0.03Y-Co₃O₄. These catalysts were characterized by X-ray diffraction (XRD), nitrogen physisorption, hydrogen temperature-programmed reduction (H₂-TPR), oxygen temperature-programmed desorption (O₂-TPD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) techniques. The results show that both Co₃O₄ and Y-Co₃O₄ exhibit spinel structure, however Y-doped Co₃O₄ catalysts are more active than bare Co₃O₄. After further modified by potassium, the 0.02K/0.03Y-Co₃O₄ reveals higher activity due to the more active sites (Co²⁺) and easier desorption of surface oxygen species than un-modified 0.03Y-Co₃O₄. In detail, the temperatures of N₂O full conversion over 0.02K/0.03Y-Co₃O₄ catalyst are 325, 350, 375°C, under the reaction atmospheres of 1%N₂O+Ar, 1%N₂O+2%O₂+Ar, 1%N₂O+2%O₂+8.2%H₂O+Ar, respectively. In addition, over 90% conversion of N₂O can be maintained at 350°C after continuous reaction for 50 h in the co-presence of oxygen and steam on K-modified Y-Co₃O₄ catalyst. There is a dynamic compensation effect between apparent activation energy (E_a) and pre-exponential factor (A) in N₂O decomposition over Y-Co₃O₄ and K-modified catalysts.