American Chemical Society
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Comparative Study on the Different Interaction Pathways between Amorphous Aluminosilicate Species and Organic Structure-Directing Agents Yielding Different Zeolite Phases

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journal contribution
posted on 2017-09-26, 00:00 authored by Tadashi Umeda, Hiroki Yamada, Koji Ohara, Kaname Yoshida, Yukichi Sasaki, Miku Takano, Satoshi Inagaki, Yoshihiro Kubota, Takahiko Takewaki, Tatsuya Okubo, Toru Wakihara
Zeolites possessing novel structures and compositions have been produced using guest organic species, which are called organic structure-directing agents (OSDAs). However, the specific roles of OSDAs have not been clarified yet. In this work, *BEA- and CHA-type zeolites are synthesized from the same starting inorganic materials but with different OSDAs, and the crystallization pathways are observed using various analytical techniques. During the synthesis of *BEA-type zeolite, the gradual evolution of the aluminosilicate structure leads to the transformation from an amorphous structure to a crystalline one. On the other hand, during the synthesis of CHA-type zeolite, a few CHA nuclei are formed in “partially-ordered amorphous species” and grow through the consumption of “buffer amorphous species” on the surfaces of CHA-type zeolite crystals. This clear difference in crystallization behaviors of the two zeolites under the same synthetic conditions is attributed to the differences in the structure-directing ability. This study demonstrates the potential of structure-directing agents to control the crystallization behaviors of zeolites and provides novel insights into zeolite crystallization behavior.