加氢精制催化剂表面纳米棒束的电子显微镜研究

Study of the Nanorod Arrays on Hydrorefining Catalyst Surface by Electron Microscopy

利用场发射扫描电镜(SEM)、高分辨透射电镜(HRTEM)、X射线能谱仪(EDX)和选区电子衍射(SAED)分析,对实验室硫化态加氢精制催化剂外表面上的纳米棒束的形貌、化学成分、晶体结构进行研究。SEM结果表明,该纳米棒束普遍分布于催化剂外表面并向外生长,纳米棒束形态较为规整,长度为500～1 500 nm,直径为200～500 nm。HRTEM结果表明,棒束由直径在40～100 nm的纳米棒聚集而成。纳米棒具有单晶结构,利用HRTEM可清晰地观察到其晶格条纹图像。利用TEM-EDX确定纳米棒束的成分为钙、氧和硫。采用TEM系列倾转的方法,获得不同取向的选区电子衍射图。根据化学成分及衍射谱中衍射斑点对应的晶体学信息及晶体取向间的夹角关系,确定该钙硫氧化合物属于六方晶系的CaSO4。硫酸钙的形成与实验装置催化剂床层中掺入的石英砂中的钙杂质有关。因此,为避免加氢过程中催化剂表面硫酸钙的形成,应对石英砂进行高温焙烧、酸洗和碱洗等预处理。

The morphologies,chemical composition and crystal structure of the nanorod arrays on the sulfurated hydrorefining catalyst surface were studied by scanning electron microscopy（SEM）,high resolution transmission electron microscopy（HRTEM）,selected area electron diffraction（SAED）and X-ray energy disperse spectroscopy（EDS）.The nanorod arrays were observed by SEM,which widely distributed on the catalyst surface.The nanorod arrays grew outward from the surface and assumed their regular shapes with lengths of 500-1 500 nm and diameter of 200-500 nm.According to the result of HRTEM,the nanorod arrays consisted of nanorods possessing single crystal structure with diameters of 40-100 nm.The image of crystal lattice fringe was also observed by HRTEM.The results of TEM-EDS showed that the nanorod arrays were composed of Ca,S and O.By means of the double-tilt method,SAED patterns with different orientations were obtained.According to the chemical composition of the nanorod arrays shown by EDS and the crystallology information from the diffraction patterns of SAED patterns,the nanorods were confirmed to be of hexagonal calcium sulphate.The formation of calcium sulphate resulted from Ca originated from quartz sands which were mixed with catalysts in the fixed bed.Therefore,in order to prevent the generation of calcium sulphate,the quartz sands should be properly pretreated by calcining at high tempreture,acid cleaning and alkali cleaning,to eliminate the influence of calcium sulphate on catalytic activity in hydro-refining process.