Yoo Won Cheol, Kumar Sandeep, Penn R Lee, Tsapatsis Michael, Stein Andreas
Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA.
J Am Chem Soc. 2009 Sep 2;131(34):12377-83. doi: 10.1021/ja904466v.
The effects of confinement on the morphological development of the zeolite silicalite-1 were studied during hydrothermal synthesis in three-dimensionally ordered macroporous (3DOM) carbon monoliths. By scheduling multiple infiltration/hydrothermal reaction (IHT) steps using precursor solutions with high (H) or low nutrient content (L) in specific sequences, it was possible to obtain various zeolite morphologies of interest for technological applications. The special morphologies are also functions of shaping and templating effects by the 3DOM carbon reactor and functions of limited mass transport in the confined reaction environment. IHT steps employing high nutrient concentrations favor nucleation, whereas those using low nutrient concentrations provide growth-dominant conditions. Observed product morphologies include polycrystalline sphere arrays for the sequence HHH..., single crystal domains spanning dozens of macropores for the sequence LLL..., and faceted silicalite-1 crystallites with dimensions less than 100 nm with the sequence HLLL.... Most of these crystallites have dimensions less than 100 nm and would be suitable building blocks for seeded zeolite membrane growth. Finally, the sequence LLL...H introduces a secondary population of particles with smaller size, so that the size distribution of zeolite crystallites in the combined population may be tuned, for example, to optimize packing of particles. Hence, by choosing the appropriate infiltration program, it is possible to control grain sizes in polycrystalline particles (spheres and opaline arrays of spheres), which alters the concentration of grain boundaries in the particles and is expected to influence transport properties through the zeolite.
在三维有序大孔（3DOM）碳块体的水热合成过程中，研究了受限环境对沸石硅沸石-1形态发育的影响。通过按特定顺序安排使用高（H）或低营养成分（L）的前驱体溶液进行多次渗透/水热反应（IHT）步骤，可以获得各种技术应用中感兴趣的沸石形态。这些特殊形态也是3DOM碳反应器的成型和模板效应以及受限反应环境中有限质量传输的函数。采用高营养浓度的IHT步骤有利于成核，而使用低营养浓度的步骤则提供生长主导条件。观察到的产物形态包括序列HHH...的多晶球阵列、序列LLL...的跨越数十个大孔的单晶域以及序列HLLL...的尺寸小于100 nm的刻面硅沸石-1微晶。这些微晶大多尺寸小于100 nm，将是用于晶种沸石膜生长的合适构建块。最后，序列LLL...H引入了较小尺寸的二次粒子群，从而可以调整组合群体中沸石微晶的尺寸分布，例如，以优化粒子的堆积。因此，通过选择合适的渗透程序，可以控制多晶颗粒（球体和球体的蛋白石阵列）中的晶粒尺寸，这会改变颗粒中晶界的浓度，并有望影响通过沸石的传输性能。
