立方介孔相含镧氧化硅的合成与表征

目的合成具有立方结构的含镧La-MCM-48介孔分子筛材料，方法以低浓度的十六烷基三甲基溴化铵为结构导向剂，在碱性条件下通过水热法合成了该物质。结果XRD测试表明当La／Si〈0．05时可以获得典型的长程有序介孔立方结构相，随La／Si比的增加，晶胞参数的增大和红外吸收光谱（FTIR）的变化为镧进入介孔分子筛骨架中提供了有力证据。N2吸附-脱附实验给出这种立方介孔材料的BET表面积为1180m^2mg^-1，BJH平均孔径为3．4nm。紫外-可见漫反射光谱（UV-vis）证明镧以一种六配位的形式存在。X射线光电子能谱（XPS）进一步证明镧以三价形式存在于立方介孔分子筛骨架中。结论合成了立方介孔相含镧氧化硅。

Synthesis and characterization of cubic mesoporous Lanthanum-containing silica

Objective:To synthesize the cubic Lanthanum-modified MCM-48 molecular sieves.Methods:In the alkaline condition,CTAB were used as template with low surfactant to inorganic precursor ratios,via a hydrothermal method to synthesize this material.Results:The X-ray diffraction indicated that the well-ordered cubic mesoporous structure was obtained when the La/Si molar ratio was less than 0.05.With the increase of La /Si molar ratio,the increase of unit cell parameters and the change of FTIR provided powerful evidences for the incorporation of Lanthanum in the framework of mesoporous molecular sieves.Nitrogen adsorption suggested that the BET surface area was 1150m2g-1 and that the average pore diameter was 3.3nm.Diffuse reflectance UV-visible(UV-vis) spectroscopy confirmed that the presence of Lanthanum was six coordinating.X-ray photoelectron spectroscopy(XPS) studies revealed that most of Lanthanum was trivalent in the framework of mesoporous molecular sieves.Conclusion:Cubic mesoporous lanthanum-containing silica is obtained successfully.