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

Zeolites have been widely used as catalysts and adsorbents, and in recent years, increasing attention has been paid to their applications related to carbon neutrality. For the rational control of zeolite functions, a deep understanding of their synthesis processes is essential. However, the crystallization mechanisms of zeolites remain only partially understood, and the design of their catalytic and adsorption properties remains challenging. In this study, various types of silica alumina sources were prepared using different approaches, including an originally developed stepwise gel preparation (SGP) method. Furthermore, the obtained starting materials were used to synthesize AEI and CHA zeolites. Zeolites synthesized by the SGP method exhibited reduced structural defects and specific aluminum distributions, resulting in high hydrothermal stability in NH₃-SCR. By employing a comprehensive analytical approach combining solid- and liquid-state NMR spectroscopy and electrospray ionization mass spectrometry, the crystallization processes of the obtained zeolites were systematically investigated. The results revealed that the unique structural distribution of aluminosilicate oligomers formed during the induction period, as well as the decomposition behavior of precursor species such as seed crystals, plays a crucial role in the formation of favorable Al distributions and the suppression of structural defect formation.