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

Various ordered and high-silica molecular sieves (including zeolites) can be synthesized by using organic structure-directing agent (SDA). Appropriate hydrophobicity of SDA molecule is particularly important in terms of effective organic-silicate interaction leading to the formation of zeolitic structures. Properly designed, bulky organic molecules play important roles to construct large pore structures. In a part of this article, an example of the molecular design of SDA as well as a successful synthesis of a novel framework structure GON by utilizing a new SDA is described. Recently, the use of inorganic reagents in addition to the organic SDAs has greatly contributed for the production of molecular sieves with new framework structures that had been believed to be difficult to synthesize. The structural features of the novel frameworks are reviewed and the following topics are introduced in the text: (1) The syntheses of pure polymorphs such as polymorph B of CIT-1/SSZ-26/SSZ-33 family (CON) and polymorph C of beta zeolite (BEC), in which the stacking sequences have been perfectly controlled. (2) The syntheses of zeolites having multi-dimensional pore systems with intersecting 14-ring and 12-ring pores, such as IM-12 and ITQ-15 (UTL). (3) Issues concerning the recovery of SDA from an as-synthesized zeolite and reuse of the recovered SDA for zeolite synthesis.