Mn_xCo_(3-x)O_4复合氧化物及改性催化剂催化分解N_2O

用共沉淀法制备了一组不同组成的MnxCo3-xO4尖晶石型复合氧化物,表面负载碱金属助剂制备改性催化剂,用于催化分解N2O.用X射线衍射(XRD)、N2物理吸附(BET)、红外光谱(FTIR)、扫描电镜(SEM)、H2程序升温还原(H2-TPR)、X射线光电子能谱(XPS)等技术表征催化剂结构.考察了复合氧化物组成、碱金属助剂类型、钾前驱物等制备参数对催化剂结构和催化活性的影响.结果表明:添加助剂K、Cs降低了催化剂表面Co、Mn元素的电子结合能,弱化了Co—O和Mn—O键,有利于氧物种的脱除,提高了催化剂活性.优化出了活性较高的催化剂K/Mn0.4Co2.6O4(K2CO3),有氧无水、有氧有水气氛400℃连续反应50 h,N2O转化率分别保持100%和74.2%,催化剂稳定性较高.

Catalytic Decomposition of N2O over MnxCo3-xO4 Mixed oxides and Modified Catalysts

Mn0.4Co2.6O4 spinel oxide was prepared by co-precipitation method, and incipiently impregnated by different potassium salts solution to prepare K-doped catalysts. These catalysts were applied in N2O decomposition reaction. The techniques such as X-ray diffraction (XRD), nitrogen physisorption, Fourier transformed infrared (FTIR), scanning electron microscopy (SEM), hydrogen temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) were used to characterize these catalysts. The effect of potassium precursors (K2CO3, KNO3, K2C2O4, and CH3COOK) and potassium loadings on catalytic activity was investigated. It is shown that the appropriate loading of potassium addition weakened the strength of Co-O and Mn-O bonds, promoted the removal of surface oxygen species, and improved the catalyst activity and stability. The most active catalyst for N2O decomposition was 0.03K/Mn0.4Co2.6O4-500(K2CO3) catalyst prepared by impregnating K2CO3 solution over Mn0.4Co2.6O4 with K/(Mn Co) atomic ratio of 0.03 and calcined at 500C, over which 100% and 74.2% conversion of N2O can be maintained at 400C after continuous running for 50h in oxygen alone and oxygen-steam together, respectively.