La 或 Ce 增强 Y型分子筛结构稳定性的机制

 采用 X 射线粉末衍射、²⁹Si 固体核磁共振、X 射线光电子能谱和扫描电镜及能谱等方法研究了 La, Ce 增强 Y 分子筛结构稳定性的差异. 结果表明, La 和 Ce 的引入均可稳定 Y 分子筛的骨架结构, 但 La 离子比含量相当的 Ce 离子更容易进入分子筛内部和抑制骨架铝的脱除, 因而对分子筛结构的稳定作用更优. 结合量子力学密度泛函计算方法, 从理论上阐述了这种增强机制, 即La 或 Ce 的引入能显著增加分子筛骨架 Al 和相邻 O 原子的作用力, 有效稳定分子筛骨架 Al 位, 并且稀土离子与分子筛间存在较强的作用力; 与 Ce 相比, La 与分子筛的相互作用更大, Al–O 作用力更强, 因此, La 比 Ce 更有利于稳定分子筛的骨架结构.

Mechanism of the Influence of Lanthanum and Cerium on the Stability of Y Zeolite

The influence of lanthanum and cerium cations on the stability of Y zeolite was studied by X-ray diffraction, X-ray photoelectron spectroscopy, solid-state NMR spectroscopy, scanning electron microscopy, and energy dispersion spectroscopy. Although the stability of Y zeolite could be enhanced by the introduction of La or Ce cation, the La showed more remarkable effect than Ce. These results were con-firmed theoretically by density functional calculation. There was a strong interaction between the rare earth species and Y zeolite clusters, which restrained the formation of extra-framework alumina and evidently enhanced the stability of Y zeolite. Furthermore, the interaction between La species and Y zeolite was stronger.