One-Step Synthesis of Hierarchical Zeolite Beta via Network Formation of Uniform Nanocrystals
One-Step Synthesis of Hierarchical Zeolite Beta via Network Formation of Uniform Nanocrystals
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DOI：
10.1021/ja108698s
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发表时间：
2011-04-13
影响因子：
15
通讯作者：
Bein, Thomas
中科院分区：
文献类型：
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作者：
Moeller, Karin;Yilmaz, Bilge;Bein, Thomas
合成了具有非常高的介孔率和介孔体积的分级介孔β沸石网络，而不需要致孔剂，产率接近100%，其形式为易于回收的微米级颗粒。这是通过利用蒸汽辅助转化（SAC）诱导成核爆发的致密凝胶合成来实现的。在合成的第一阶段期间，形成单独的均匀尺寸的β沸石纳米颗粒，其随后凝结成显示均匀中孔的多孔网络。最终产物由从沸石β的20 nm晶域组装的分级自持宏观沸石聚集体组成。所得材料中沸石晶体的小尺寸产生具有约13 nm的主要孔径的中孔。在不牺牲微孔性（通常大于0.20 mL/g）的情况下获得630和750 m2/g之间的大表面积和高达0.9 mL/g的总孔体积。晶化条件进行了优化，为不同的Si/Al比在10和33之间。如果在蒸汽辅助转化过程中存在的水量被充分调节，则在170-180 ℃下仅在几个小时内实现向分级沸石β的完全转化。这种致密凝胶蒸汽转化方法被证明是在单个步骤中制造分级沸石β网络的高效策略。
A hierarchical mesoporous network of zeolite beta with very high micropore as well as mesopore volume was synthesized without the need of a porogen at near 100% yield in the form of easily retrievable micrometer-sized particles. This was achieved by a dense-gel synthesis utilizing steam-assisted conversion (SAC) to induce a burst of nucleation. During the first phase of the synthesis, individual, evenly sized zeolite beta nanoparticles are formed that subsequently condense into a porous network displaying uniform mesopores. The final product consists of hierarchical self-sustaining macroscopic zeolite aggregates assembled from 20 nm crystalline domains of zeolite beta. The small size of the zeolite crystals in the resulting materials gives rise to mesopores with dominant pore sizes of about 13 nm. Large surface areas between 630 and 750 m(2)/g and total pore volumes up to 0.9 mL/g were obtained without sacrificing the microporosity (usually larger than 0.20 mL/g). Crystallization conditions were optimized for different Si/Al ratios between 10 and 33. A complete conversion into hierarchical zeolite beta was achieved in only a few hours at 170-180 degrees C if the amount of water present during the steam-assisted conversion was adequately adjusted. This dense gel steam conversion process proves to be a highly efficient strategy for fabricating hierarchical zeolite beta networks in a single step.