Ce-EU-1分子筛的合成和表征

Synthesis and Characterization of Ce-EU-1 Zeolites

采用水热法,以溴化六甲双铵(HMBr2)为模板剂,硅溶胶、偏铝酸钠为硅铝源,以六水硝酸铈为铈源合成了稀土Ce-EU-1分子筛,并通过XRD、FTIR、紫外-可见漫反射光谱、热重分析(TG-DTG)和氮气吸附-脱附等测试手段对合成样品的孔道结构、物化性能及Ce的存在状态进行了表征。XRD结果表明,合成样品不仅具有很高的纯度和结晶度,为典型的立方有序排列的EU-1结构,而且部分Ce已取代Si或Al进入微孔分子筛的骨架。样品的FTIR图谱在980cm-1附近有明显的Si—O—Ce特征吸收峰,证明Ce存在于分子筛的骨架中。紫外-可见漫反射图谱显示,在253nm附近出现O—Ce之间的电子跃迁特征峰,进一步证明了Ce进入了分子筛骨架。氮气吸附-脱附结果表明了Ce的掺入对分子筛的物化性能和孔道结构产生了影响。同时考察了镧系其他金属离子(Ln:La、Nd、Sm和Gd)对EU-1分子筛的影响,发现随着镧系离子半径的减小,Ln-EU-1分子筛的相对结晶度逐渐降低,晶胞体积减小。

The Ce-EU-1 zeolite was successfully synthesized by hydrothermal method,with HMBr2 as template,silica sol as Si source,sodium aluminates as Al source,and cerium（Ⅲ） nitrate hexahydrate as Ce source.The pore structure,the properties,and the existence state of Ce were characterized by XRD,FTIR,UV-Vis DRS,TG-DTG and N2 adsorption-desorption.The results of XRD indicated that the sample with high purity and crystallinity,not only possessed the microporous EU-1 structures and ordered cubic arrangements,but also Ce had partially displaced Si or Al and to get into the framework of microporous molecular sieve.The FTIR spectrum had the feature absorbtion peak for Si—O—Ce at 980cm-1,which confirmed Ce was located in the framework of EU-1 zeolite.The UV-Vis DRS spectrum showed a characteristic peak at about 253nm for the electronic transition between O and Ce,that further verified Ce was incorporated into the framework of EU-1 zeolite.The results of N2 adsorption-desorption showed that the incorporation of Ce into zeolite EU-1 had an impact on its pore structure.Moreover,effects of other metal ions（Ln：La,Nd,Sm and Gd） on EU-1 zeolite systems were studied.With decreasing the radius of rare earth ions,the relative crystallinity and unit cell volume of EU-1 zeolite samples reduced,respectively.