One-Step Synthesis of Hierarchical Zeolite Beta via Network Formation of Uniform Nanocrystals
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- 作者：Karin M枚ller ; Bilge Yilmaz ; Richard M. Jacubinas ; Ulrich M眉ller ; Thomas Bein
- 刊名：Journal of the American Chemical Society
- 出版年：2011
- 出版时间：April 13, 2011
- 年：2011
- 卷：133
- 期：14
- 页码：5284-5295
- 全文大小：1271K
- 年卷期：v.133,no.14(April 13, 2011)
- ISSN：1520-5126
文摘
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 m2/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鈭?80 掳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.