(114a) Simple Synthesis of Zeolites: A Seed-Assisted, OSDA-Free Approach

Organic structure-directing agents (OSDAs) have enabled us to synthesize zeolites with novel framework types.   The number of the framework types approved by the Structure Commission of IZC is more than 190.   For the zeolites synthesized with OSDAs, calcination (or alternative process) is indispensable as post-treatment, which causes the increases of the production cost as well as energy consumption and environmental load.  Practically, OSDA-free synthesis of zeolites has been one of the most important topics for the commercialization of zeolites.  Thanks to the development of OSDA-free routes, several useful zeolites have been commercialized so far.     

            Recently, exciting topics were reported; several zeolites that had been believed that OSDAs must be used for the synthesis, such as *BEA [1, 2], RTH [3] and MTW [4] zeolites, could be synthesized without adding OSDAs but with the seed crystals.  We have investigated the OSDA-free synthesis of *BEA zeolite [5].  The synthesis region could be further broadened although one synthesis point had been reported so far [1], and the influence of several parameters such as Si/Al ratios of seeds and heating time on the product was elucidated [5].  In the seed-free condition, the gel yielded MOR zeolite after long heating.  More importantly, the “green” production was demonstrated by employing the product of the OSDA-free synthesis as seeds [5].  The formation process, especially the role of the seed crystals, was further investigated by carefully observing the intermediate products [6].     Since these zeolites contain more Al in the frameworks, compared with the ones synthesized with OSDAs, they can be used as novel adsorptive materials after suitable post-treatment method.

            Now one of the most important questions is; which zeolites can be synthesized without OSDAs and how can we do so?  In this presentation, our successes in broadening the zeolite types [7] are reported, which is based on a working hypothesis with considering composite building units in zeolites. 

References

[1] Xie, B.; Song, J.; Ren, L.; Ji, Y.; Li, J.; Xiao, F.-S. Chem. Mater. 2008, 20, 4533–4535.

[2] Majano, G.; Delmotte, L.; Valtchev, V.; Mintova, S. Chem. Mater. 2009, 21, 4184–4191.

[3] Yokoi, T.; Yoshioka, M.; Imai, H.; Tatsumi, T. Angew. Chem., Int. Ed. 2009, 48, 9884–9887.

[4] Iyoki, K.; Kamimura, Y.; Itabashi, K.; Shimojima, A.; Okubo, T. Chem. Lett. 2010, 39, 730–731.

[5] Kamimura, Y.; Chaikittisilp, W.; Itabashi, K.; Shimojima, A.; Okubo, T. Chem. Asian J. 2010, 5, 2182–2191.

[6] Kamimura, Y.; Tanahashi, S.; Itabashi, K.; Sugawara, A.; Wakihara, T.; Shimojima, A.; Okubo, T. J. Phys. Chem. C  2011, 115, 744–750.

[7] Kamimura, Y.; Itabashi, K.; Sugawara, A.; Okubo, T. Microporous and Mesoporous Materials., in press.