A rapid synthesis of Hf-Beta zeolite as highly active catalyst for Meerwein-Ponndorf-Verley reduction by controlling water content of precursor gel
A rapid synthesis of Hf-Beta zeolite as highly active catalyst for Meerwein-Ponndorf-Verley reduction by controlling water content of precursor gel
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DOI：
10.1016/j.micromeso.2022.111743
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发表时间：
2022-02
影响因子：
5.2
通讯作者：
Taichi Nakamura;Y. Kamiya;Ryoichi Otomo
中科院分区：
文献类型：
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作者：
Taichi Nakamura;Y. Kamiya;Ryoichi Otomo
在Meerwein-Ponndorf-Verley （MPV）还原和其他重要的有机反应中，Hf-Beta是一种很有前景的活性Lewis酸催化剂。然而，传统的水热合成hf - β的方法不可避免地需要繁琐的四乙氧基硅烷水解过程和较长的结晶周期。在本研究中，我们采用降低前驱体凝胶含水量的合成方法，成功地以气相二氧化硅为硅源，大大缩短了hf - β的结晶周期。采用H2O/SiO2= 1.4 ~ 7.6的前驱体凝胶，研究了前驱体凝胶含水量对Hf- β结晶、Hf掺入沸石骨架及催化性能的影响。低含水量有利于加速结晶，但不利于Hf进入沸石骨架，导致催化活性较差。在种子晶体的辅助下，在H2O/SiO2= 6.4的前驱体凝胶中，在24 h内得到了骨架Hf含量较大的Hf- β。与传统水热法合成的Hf- β、Zr-和sn - β相比，以这种方式合成的Hf- β对MPV的还原具有更高的催化活性。
Hf-Beta is a promisingly active Lewis acid catalyst for Meerwein-Ponndorf-Verley (MPV) reduction and other important organic reactions. However, the conventional hydrothermal synthesis of Hf-Beta inevitably requires the troublesome procedure for hydrolysis of tetraethoxysilane and the long period to complete crystallization. In the present study, we applied a synthetic approach of reducing water content of precursor gel and succeeded in considerably shortening the period for crystallization of Hf-Beta using fumed silica as silicon source. By using precursor gel with H2O/SiO2= 1.4–7.6, effect of water content of precursor gel on the crystallization of Hf-Beta, the incorporation of Hf into the zeolite framework, and the catalytic performance were thoroughly investigated. Low water content was favorable for accelerating the crystallization, but unfavorable for the incorporation of Hf into the zeolite framework, resulting in poor catalytic activity. With the assistance of seed crystal, Hf-Beta with a relatively large amount of framework Hf was obtained from the precursor gel with H2O/SiO2= 6.4 in 24 h. Hf-Beta synthesized in this way showed higher catalytic activity for MPV reduction than Hf-Beta as well as Zr-, and Sn-Beta synthesized by the conventional hydrothermal method.