Microwave-assisted hydrothermal synthesis of nanozeolites with controllable size
Microwave-assisted hydrothermal synthesis of nanozeolites with controllable size
复制标题
微波辅助水热合成尺寸可控的纳米沸石
DOI：
10.1016/j.micromeso.2008.11.005
复制
发表时间：
2009-03-01
影响因子：
5.2
通讯作者：
Tang, Yi
中科院分区：
文献类型：
--
作者：
Hu, Yuanyuan;Liu, Chong;Tang, Yi
在本工作中，提出了一种微波辅助的两步水热过程，成功地制备了各种沸石纳米晶（例如，silicalite-1、ZSM-5、LTL、ZSM-5和LTA）。详细研究了凝胶组成（如水含量、碱度、SiO2/Al 2 O3比）以及水热合成条件（温度和时间）对沸石纳米晶尺寸的影响。研究发现，较高的合成温度和较长的反应时间有利于所涉及的沸石纳米晶的生长。然而，凝胶组成对不同种类纳米沸石的影响非常复杂。对于在低碱度体系中结晶的纳米沸石（例如，ZSM-5、ZSM-5和LTA），增加碱度和降低水含量都加速了它们的成核过程，从而导致它们的晶体尺寸减小。相反，对于在高碱度体系中制备的那些（例如，LTL和silicalite-1），可以观察到相反的趋势。初始凝胶中SiO2/Al 2 O3的变化对纳米ZSM-5和LTL分子筛的尺寸有较大影响，但对纳米ZSM-5分子筛的尺寸影响不大。这些结果将为充分开发各种纳米沸石的传统和非传统应用提供坚实的基础。(C)2008年爱思唯尔公司All rights reserved.
In the present work, a microwave-assisted two-step hydrothermal procedure was proposed successfully to prepare various zeolite nanocrystals (e.g., silicalite-1, ZSM-5, LTL, BEA and LTA) with controllable size, morphology and SiO2/Al2O3 ratio. The effects of the starting gel composition (such as water content, alkalinity and ratio of SiO2/Al2O3) as well as the hydrothermal synthesis condition (temperature and time) on the size of the zeolite nanocrystals have been studied in detail. It is found that high synthesis temperature and long reaction time benefit the growth of all the referred zeolite nanocrystals. However, the effects of the gel composition are very complex to different kinds of nanozeolites. For the nanozeolites crystallized in low alkalinity systems (e.g.. ZSM-5, BEA and LTA), both increasing the alkalinity and decreasing the water content accelerate their nucleation process and thereby result in the decrease of their crystal size. On the contrary, for those prepared in high alkalinity systems (e.g., LTL and silicalite-1), an inversed trend could be observed. Moreover, the change of SiO2/Al2O3 ratio in the starting gel greatly affects the size of nanozeolite ZSM-5 and LTL, but slightly influences that of nanozeolite BEA. These results would provide a solid foundation to fully exploit the traditional and untraditional applications of various nanozeolites. (C) 2008 Elsevier Inc. All rights reserved.