Sustainable Synthesis of Zeolites without Addition of Both Organotemplates and Solvents
Sustainable Synthesis of Zeolites without Addition of Both Organotemplates and Solvents
复制标题
不添加有机模板和溶剂的沸石可持续合成
DOI：
10.1021/ja500098j
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发表时间：
2014-03-12
影响因子：
15
通讯作者：
Xiao, Feng-Shou
中科院分区：
文献类型：
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作者：
Wu, Qinming;Wang, Xiong;Xiao, Feng-Shou
可持续、环保的沸石合成技术的发展备受关注，因为水热合成沸石中有机模板和溶剂的使用是实现绿色、可持续合成方法的主要障碍。最近，无有机模板合成方法的引入可以避免使用有机模板，但仍然需要水作为溶剂；另一方面，无溶剂路线具有显着减少废水污染量的潜力，但有机模板仍然存在。在这项工作中，我们展示了有机模板和无溶剂条件的组合策略来合成铝硅酸盐沸石 Beta 和 ZSM-5（S-Beta 和 S-ZSM-5），这是与工业相关的两种最重要的沸石。通过 XRD 图案、SEM 图像、N-2 吸附等温线、UV-拉曼光谱以及 Si-29 和 Al-27 MAS NMR 光谱对样品进行了彻底表征。结果表明，S-Beta和S-ZSM-5沸石与水热条件下合成的常规Beta和ZSM-5沸石（C-Beta和C-ZSM-5）表现出几乎相同的结构参数（例如BET表面积和孔体积）以及异丙苯裂解和间二甲苯异构化催化性能。 S-Beta 和 S-ZSM-5 的无有机模板和无溶剂合成在低压状态下进行，不含有害气体，产品收率高，起始原料消耗效率高。与目前用于 C-Beta 和 C-ZSM-5 的传统方法相比，这些优点加上非常简单的程序，为高度可持续的沸石合成方案开辟了道路。非常有趣的是，这种简单的合成是理解沸石结晶的一个很好的模型。详细表征表明，S-Beta晶体是由沸石结构单元（主要是4MR）组装而成，而骨架中的SMR只是在S-ZSM-5结晶过程中形成，而不是存在于起始固体混合物中。在结晶过程中，少量的水对于二氧化硅和/或铝硅酸盐物质的水解和缩合起着重要作用。
The development of sustainable and environmentally friendly techniques for synthesizing zeolites has attracted much attention, as the use of organic templates and solvents in the hydrothermal synthesis of zeolites is a major obstacle for realizing green and sustainable synthesis ways. Recently, the introduction of the organotemplate-free synthesis method allowed avoiding the use of organic templates, but water as solvent was still required; solvent-free routes on the other hand beared the potential to significantly reduce the amount of polluted wastewater, but organic templates were still present. In this work, we have demonstrated a combined strategy of both organotemplate- and solvent-free conditions to synthesize aluminosilicate zeolites Beta and ZSM-5 (S-Beta and S-ZSM-5), two of the most important zeolites relevant for industry. The samples are thoroughly characterized by XRD patterns, SEM images, N-2 sorption isotherms, UV-Raman spectra, and Si-29 and Al-27 MAS NMR spectra. The results demonstrate that S-Beta and S-ZSM-5 zeolites exhibit almost the same textural parameters (e.g., BET surface area and pore volume) and catalytic performance in cumene cracking and m-xylene isomerization as those of conventional Beta and ZSM-5 zeolites synthesized under hydrothermal conditions (C-Beta and C-ZSM-5). The organotemplate- and solvent-free syntheses of S-Beta and S-ZSM-5 take place at a low-pressure regime and are free of harmful gases as well as give high product yields together with highly efficient consumption of the starting raw materials. These advantages plus the very simple procedures opened the pathway to a highly sustainable zeolite synthesis protocol compared to conventional methods currently employed for C-Beta and C-ZSM-5. Very interestingly, this simple synthesis is a good model for understanding zeolite crystallization. The detail characterizations indicate that the S-Beta crystals are formed from the assembly of zeolite building units, mainly 4MRs, while the SMRs in the framework are just formed in the crystallization of S-ZSM-5, rather than existence in the starting solid mixture. During the crystallization processes, small traces of water play an important role for the hydrolysis and condensation of silica and/or aluminosilicate species.