日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

Amorphous network structures formed under hydrothermal conditions, prior to the onset of crystallization of microporous aluminosilicate zeolites (LTA, FAU, MOR and MFI), are determined by employing high-energy X-ray diffraction (HEXRD) technique. It has been shown that the precursors containing Al, in perticular with lower Si/Al ratio, have a large fraction of smaller rings compared to the amorphous silica. This ring statistics is similar to that of the final products where LTA and FAU have a large fraction of 4R (R: ring), whereas MOR and MFI have large fractions of 5R. Furthermore, the use of reverse Monte Carlo modeling on HEXRD data suggests that even numbered rings, especially 4R and 6R, which are the dominant aluminosilicate rings in LTA, have already been produced in the precursor. The obtained RMC model provides a better understanding of the nature of amorphous network structure formed during the initial stages of the crystallization process, and is applicable to any type of solid formed via an amorphous intermediate. We believe that this method is likely to show the structural pathway for the formation of microporous materials.