XRD分析CuZnAl催化剂中活性组分的晶粒组成

XRD analysis of crystallite size and content of CuZnAl catalyst

利用X射线衍射(XRD)分析了合成气制甲醇CuZnAl催化剂的物相,结果表明:主要为单斜相的CuO,未见ZnO和Al_2O_3的衍射峰。单斜相CuO的衍射峰可以分峰为较窄的衍射峰和弥散衍射峰。利用Bruker的XRD数据分析软件EVA、TOPAS计算这两部分对应的晶粒尺寸和含量,分别为5～9nm、含量20%～30%的大晶粒和1～2nm、含量70%～80%的微细晶粒。把样品中的活性组分区分为微细晶粒和大晶粒,而不是把微细晶粒作为非晶相,这更能准确反映催化剂的组成特点。催化剂性能评价的结果表明:合成气制备甲醇时,微细晶粒含量越高、大晶粒尺寸相对较小的样品,其催化性能更好。

The crystal phase of CuZnAl catalyst for methanol synthesis is characterized by x-ray diffraction (XRD). The result indicates that the main phase is monoclinic phase CuO, and the diffraction peaks of ZnO and Al2O3 are not found. The diffraction peaks of CuO can be divided into narrow peaks and broad peak. The crystallite size and content of the two parts are respectively calculated by EVA and TOPAS softwares of Bruker. The crystallite size calculated from narrow peaks is 5-9nm and its content is 20%-30% while the size calculated from broad peaks is 1-2nm and its content is 70%-80%- which indicates that the active compositions in the sample include two kinds of crystalline in nature. On the basis of the relationship established between XRD result and the catalyst evaluation data, it is suggested that the catalyst, which has smaller crystallite with higher content and bigger crystallite with relatively small size, perform better.