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

The use of organic structure-directing agent (SDA) is a potential tool to obtain highsilica molecular sieves (including zeolites). With respect to the contribution of the organic SDAs, it is important to understand the properties of these molecules that influence the resulting zeolite phase. Such information allows for improvements in efforts to generate zeolite structures "by design". In this article, various characters of organic SDAs (mainly quaternary ammonium compounds) are correlated to the ability for structure-direction in zeolite synthesis. The following factors of SDA molecule are taken into consideration: hydrophobicity, size, shape, charge distribution, and chemical stability. Appropriate hydrophobicity of SDA molecule is particularly important in terms of organic-silicate interaction. It is also important to consider the chemical stability of SDA molecule to design new SDA structures. The chemical decomposition pathways of SDA molecules under basic conditions are carefully investigated; the Hofmann degradation and alkaline hydrolysis are actually observed in some cases.