Fe3O4的X射线微结构特征与催化活性间的关系

湿法工艺制备的不同晶型Fe2O3, 经水煤气还原后Fe3O4的X射线衍射微结构特征, 用分析微应变和晶粒尺寸的Voigt函数单峰分析法进行了测定。Fe3O4微应变大小同催化活性间存在一种对应关系。γ-Fe2O3还原的Fe3O4比α型还原的有更大的晶格畸变, 在325℃, 500空速条件下, CO转化率达97%以上, 比后者高出30%多。这种畸变结构在工业催化反应条件下能长期稳定, 但经600℃高温处理后, 畸变减小,活性下降。湿法工艺可以获得具有不同活性的Fe3O4前身, γ-Fe2O3与Fe3O4晶体结构上的类似, 使它在还原过程中, 能把这种高活性的结构状态保留下来。

The relationship between XRD microstructure characteristic and catalytic activity of Fe3O4

In this study we investigated the microstructure characteristic of Fe3O4 water-gas shift catalyst prepared by different crystalline forms of Fe2O3 with the method of line-profile analysis based on the Voigt function. We found a relationship which exists between the lattice distortions of Fe3O4 and their catalytic activities. Fe3O4 reduced from γ-Fe2O3 has larger lattice distortion than that from α-Fe2O3. At the temperature of 325℃, the conversion percentage of water-gas shift catalyst of Fe3O4 reduced from γ-Fe2O3 is 30% higher than that of Fe3O4 reduced from α-Fe2O3. Under industrial reacting conditions, such a distortion structure can keep stable for a long time. However, after being aged at 600℃ for 2h, its distortion and low temperature activity obviously decreases. The various wet-methods are important technique to obtain high activity water-gas shift catalyst. But only γ-Fe2O3 which is analogy to Fe3O4 in structure can keep its high activity state during reduction process.