Influence of the kind of layered disodium disilicates on the formation of silica-organic mesostructured materials

Silica-based mesostructured materials are formed using hydrated α-sodium disilicate and hexadecyltrimethylammonium (C ₁₆TMA) chloride at various C ₁₆TMA/Si molar ratios, and compared with those from kanemite. When the C ₁₆TMA/Si ratios are 0.2, 0.5, 0.7, and 1.0, 2-D hexagonal structures are formed from hydrated α-sodium disilicate though the structures are collapsed on calcination. Less ordered hexagonal structures with straight channels arranged in one direction are formed when the C ₁₆TMA/Si ratio exceeds 1.0. In the case of the reactions of kanemite with C ₁₆TMA ions, lamellar mesostructures are formed at the ratios higher than 0.5, whereas a 2-D hexagonal structure is formed only at the ratio of 0.2. Mesoporous silica (SSW-1) derived from hydrated α-sodium disilicate is prepared at lower pH without acid treatment when the C ₁₆TMA/Si ratio is 2.0. The volume occupied by the headgroups of C ₁₆TMA ions in hydrated α-sodium disilicate should be larger than that in kanemite because the distance between Si-O ^- sites in the bending direction of hydrated α-sodium disilicate is longer than that of kanemite due to the unique layered silicate structure.