VIBRATIONAL SPECTROSCOPIC STUDY OF THE EVOLUTION OF THE FRAMEWORK OF THE ZEOLITE FERRIERITE

Ferrierite is distinct from other zeolites in that it does not contain four-membered aluminosilicate rings, but is composed of five-, six-, eight-, and ten-membered rings. It is difficult to synthesize ferrierite from a completely inorganic system, whereas the addition of organic structure directing agents such as pyrrolidine greatly speeds up the process. Using Raman spectroscopy, we have investigated the evolution of the ferrierite structure from an inorganic and organic gel system. In the inorganic system, the gel structure is primarily made up of four-membered aluminosilicate rings, and addition of pyrrolidine results in transformation of the gel to a more ferrierite-like structure. The NH2+ rocking mode of the pyrrolidine associated with the gel undergoes significant changes during nucleation. These data are consistent with a zeolite growth process which proceeds from a global ordering of the aluminosilicate gel at the initial stages to the subsequent buildup of smaller domains and finally to the assembly of the specific units characteristic of the zeolite itself.