Hierarchical Mesoporous Zeolites: Direct Self-Assembly Synthesis in a Conventional Surfactant Solution by Kinetic Control over the Zeolite Seed Formation

• Published in: Chemistry : a European journal Vol. 17; no. 51; pp. 14618 - 14627
• Main Authors: Zhu, Yan, Hua, Zile, Zhou, Jian, Wang, Lijun, Zhao, Jinjin, Gong, Yun, Wu, Wei, Ruan, Meiling, Shi, Jianlin
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 16.12.2011; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: aldol condensations; Chemistry; Ethanol; Ethyl alcohol; Formations; heterogeneous catalysis; Hexadecyl trimethyl ammonium bromide; kinetics; Mathematical models; Seeds; Self assembly; surface chemistry; surfactants; Zeolites
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201101401

By kinetic control over the zeolite seed formation, we report the direct fabrication of hierarchical mesoporous zeolites using hexadecyl trimethyl ammonium bromide (CTAB) as the soft template in a conventional solution route. Nanometer‐sized, subnanocrystal‐type zeolite seeds with a high degree of polymerization are essential to prevent the formation of a separate amorphous mesoporous phase and the phase separation between the mesophase and zeolite crystals in the presence of CTAB and a certain amount of ethanol. The mechanisms for the formation of hierarchically porous zeolites in the solution process, including the effect of mother liquid aging, formation of subnanocrystal zeolite seeds and their self‐assembly effect with CTAB, and the role of ethanol are proposed and discussed in detail. The prepared mesoporous ZSM‐5 zeolite showed much higher catalytic activity than conventional counterparts for aldol condensations involving large molecules, especially in the synthesis of vesidryl. Subnanocrystals were used as zeolite seeds for the synthesis of hierarchical mesoporous zeolites under the direction of hexadecyl trimethyl ammonium bromide (CTAB; see scheme). Different interaction models between mesoporogen and zeolite precursor were subject to kinetics.