A Study on Synthesis of Silicates by High-Pressure Hydrothermal Method using Organic Template Reagents

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This study was carried out on the influences of pressure conditions and organic ions on the morphology of the silicates prepared by high-pressure hydrothermal method. Also, the physicochemical environmental characteristics of the micropores of zeolites were investigated by using the rare earth ion with excellent luminescence properties as a probe.(1) Influence of the organic template ions on the morphology of resulting zeolitesA series of unsymmetrical tetraalkyl ammonium salts with the composition formula of R_3R'N^+X^- (R=R') were synthesized and were used to prepare the pentasil-type ZSM-5 zeolite. The composition and morphology of the zeolites obtained by using them were considerably different from those of ZSM-5 zeolite. This indicates that the unsymmetrical ammonium salts possess a possibility for the formation of new zeolites.(2) Physicochemical environment of the micropores of zeolitesThe zeolites ion-exchanged with Eu^<3+> ions showed a red emission bands based on the f-f transition, and this luminescence properties were modified by introductions of organic ligands such as 2, 2' -bipyridene, 2, 6-pyridinecarboxylic acid, and acetylacetone. Particularly, the luminescence intensity was considerably increased. The symmetry around the Eu^<3+> ion in zeolites was discussed on the basis of the luminescence patterns.