摘要
用一步水热、分步水热、浸渍等方法分别制备Y-Co_3O_4复合氧化物,用于催化分解N_2O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-Co_3O_4复合氧化物,在优化出的催化剂(0. 03YCo_3O_4)表面浸渍K_2CO_3溶液,制备K改性催化剂(0. 02K/0. 03Y-Co_3O_4)。用X射线衍射(XRD)、N_2物理吸附、H_2程序升温还原(H_2-TPR)、O_2程序升温脱附(O_2-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,Co_3O_4和Y-Co_3O_4同为尖晶石结构,但Y-Co_3O_4的催化活性显著高于Co_3O_4。K改性增加了催化剂表面的活性位(Co^(2+)),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N_2O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N_2O分解率保持90%以上,稳定性较高。研究发现,Y-Co_3O_4及K改性催化剂上N_2O分解反应的Ea和lnA之间存在动力学补偿效应。
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 0.03 Y-Co3O4 was impregnated by K2CO3 solution to prepare K-modified catalyst and named as 0.02 K/0.03 Y-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 showthat 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 0.02 K/0.03 Y-Co3O4 reveals higher activity due to the more active sites(Co2+)and easier desorption of surface oxygen species than un-modified 0.03 Y-Co3O4.In detail,the temperatures of N2O full conversion over 0.02 K/0.03 Y-Co3O4 catalyst are 325,350,375℃,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℃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(Ea)and pre-exponential factor(A)in N2O decomposition over Y-Co3O4 and K-modified catalysts.
作者
赵天琪
高强
李和健
徐秀峰
ZHAO Tian-qi;GAO Qiang;LI He-jian;XU Xiu-feng(Institute of Applied Catalysis,School of Chemistry and Chemical Engineering,Yantai University,Yantai 264005,China)
出处
《燃料化学学报》
EI
CAS
CSCD
北大核心
2019年第4期446-454,共9页
Journal of Fuel Chemistry and Technology
基金
supported by Shandong Natural Science Foundation(ZR2017M B020)
raduate Innovation Foundation of Yantai University(YDYB1909)
