Combining\nElectron Microscopy and Elemental Mapping\nfor the Investigation of Zeolite Crystallization

An elemental mapping method using\nelectron microscopy with energy\ndispersive X-ray spectroscopy has proved to be a versatile tool to\ntrack the crystallization of zeolites. We have observed that disparities\nin local concentration of inorganic structure-directing agent (e.g.,\nalkali metal) is an effective indicator of the degree of crystallization\nin zeolites. In this study, we demonstrate this approach for zeolite\nZSM-22 (TON) with very small crystal sizes (<1 μm), where\nthe high spatial resolution of elemental mapping in combination with\nscanning transmission electron microscopy allows one to obtain a high\nsensitivity for the detection of early-stage crystals. The crystallization\nof TON proceeds through a primary alkali rich amorphous phase that\nevolves to a secondary poorly crystalline phase which already possesses\nthe composition of the final zeolite crystals. This fact gives us\nthe possibility to determine the onset of disorder-to-order transitions\nin individual crystals of materials, that are amorphous by X-ray diffraction.