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Direct Cationic and Nonionic Templating Synthesis of Mesoporous Zsm-5 Using Amphiphilic Silylated Surfactant

Rino R. Mukti, Hirotomo Hirahara, Atsushi Shimojima, and Tatsuya Okubo. Department of Chemical System Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

Hierarchical porous structure has been on demand over the past decade. Until now, the most significant progress has been achieved with films while the development of hierarchical porous solids particularly possessing ordered micro- and mesopores is still expecting discoveries and new applications. There have been a number of reports thus far showing that the use of hierarchical zeolite in catalytic reaction has been always superior compared to the one of conventional zeolite. The alkylation of benzene with isopropanol was catalytically favored and selective by using hierarchical Beta zeolite even with undefined mesostructure [1]. Having wormhole-like mesoporous, hierarchical MFI zeolite was reported to be free from deactivation during such reactions as isomerization, cracking, esterification and condensation [2, 3], therefore the synthesis of designed hierarchical zeolite has been very challenging. The achievement of using hard-templating synthesis may result an interesting material with zeolite crystallinity on the pore walls of Al/SBA-15/CMK-5 nanocomposite as elucidated by electron diffraction technique [4]. Moreover, the synthesis resulted from soft-templating method has shown a breakthrough by applying the tunable cationic amphiphilic surfactant with triethoxysilyl group which was self-assembled with zeolite precursors, i.e. assuming the presence of a covalent interaction [5]. However, it should be noted that the resulting composites with inter-connecting particles (physical mixtures) properties are not proposed as the final product, hence intra-connecting particles with new morphology should be designed. In order to demonstrate such properties, the material must show long and short range orders. The relatively intense zeolite crystallinity may bring the result into separated phases while the relatively weak zeolite crystallinity might suggest the interaction with mesopore walls. We are introducing the synthesis of mesoporous ZSM-5 (aluminosilicate zeolite with MFI type) templated by supramolecular nonionic pathway under basic condition. The nonionic surfactant used was silylated oligomeric alkyl(polyethylene oxide). In comparison to cationic route, the nonionic surfactant from block copolymer has more advantages to be used as mesoporous structure-directing agent where this includes larger structural features from solution organization and tunable continuous ordering properties. The new nonionic amphiphilic silylated surfactant can be applied in the synthesis of mesoporous ZSM-5. The nonionic surfactant may feature as nontoxic, biodegradable and low cost raw material if used in large scale.


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