Hydrophilicity/hydrophobicity modulated synthesis of nano-crystalline and hierarchically structured TS-1 zeolites
Hydrophilicity/hydrophobicity modulated synthesis of nano-crystalline and hierarchically structured TS-1 zeolites
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纳米晶和分级结构 TS-1 沸石的亲水/疏水调制合成
DOI：
10.1039/c6ce02435a
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发表时间：
2017-03-14
期刊：
影响因子：
3.1
通讯作者：
Shi, Jianlin
中科院分区：
文献类型：
--
作者：
Ge, Tongguang;Hua, Zile;Shi, Jianlin
纳米晶体和分级结构材料被认为是提高微孔沸石传质效率的两个重要选择。在此，我们首先提出了一种高效的凝胶结晶方法，用于合成 TS-1 纳米晶体，其质量产率高达 97.4%，体积产率约为 0.36 g ml−1。所得的 TS-1 纳米沸石 (un-TS-1) 具有均匀且可调的粒径，范围为 80 nm 至 2.0 μm。与直接水热法合成的TS-1对应物(ht-TS-1)相比，所获得的un-TS-1材料在稀H2O2作为氧化剂的1-己烯环氧化和苯酚羟基化反应中表现出相当或改进的催化性能。更重要的是，提出了一种表面亲水性/疏水性调节机制，以说明在相同合成条件下un-TS-1纳米晶和单晶ZSM-5 HSZ的不同结构演化途径：由于Ti对Si的等价取代，TS-1的相对较强的疏水性被认为是形成 纳米晶 TS-1，与三价 Al 取代 Si 产生的亲水性更高的 ZSM-5 HSZ 相比。相对亲水性的含Al TS-1 和Fe 掺杂silicalite-1 HSZ 的成功合成为这一机制提供了进一步的支持。
Nanosized crystals and hierarchically structured materials are considered to be two important options to enhance the mass transportation efficiency in microporous zeolites. Herein, we first present a highly efficient gel-crystallization approach for the synthesis of TS-1 nanocrystals with an exceptionally high mass yield of up to 97.4% and a volume yield of ∼0.36 g ml−1. The resultant TS-1 nanozeolites (un-TS-1) possess uniform and tunable particle sizes from 80 nm to 2.0 μm. Compared to the TS-1 counterparts (ht-TS-1) synthesized by a direct hydrothermal method, the obtained un-TS-1 materials showed comparable or improved catalytic performance for epoxidation of 1-hexene and hydroxylation of phenol with dilute H2O2 as the oxidant. More importantly, a surface-hydrophilicity/hydrophobicity-modulated mechanism has been proposed to illustrate the distinct structural evolution pathway of un-TS-1 nanocrystals and single-crystalline ZSM-5 HSZs under identical synthetic conditions: the relatively stronger hydrophobicity of TS-1 due to the equal-valence substitution of Ti for Si, is suggested to be responsible for the formation of nanocrystalline TS-1, in comparison with ZSM-5 HSZs of higher hydrophilicity resulting from the tri-valence Al substitution for Si. The successful syntheses of relatively hydrophilic Al-containing TS-1 and Fe-doped silicalite-1 HSZs offer further support to this mechanism.