Raman spectroscopic studies of aqueous tetramethylammonium silicate solutions

Abstract The influence of cations on aluminosilicate zeolite formation is well recognized. This Raman study showed that on a molecular level, there is a significant difference in the type of silicate species that are solubilized by tetramethylammonium hydroxide and sodium hydroxide at certain hydroxide ion concentrations. A cubic, cage‐like silicate species is formed in 1.0–1.4 M tetramethylammonium hydroxide, whereas no such species was formed in alkali metal hydroxide at any concentration. Band assignments for the cubic species [(CH3)4N]8Si8O20 are made from the Raman and infrared spectroscopic data. Elucidation of such structural effects by Raman spectroscopy can help explain the unique influence of the cation on zeolite formation.