Intergrowth Structure of Zeolite Crystals as Determined by Optical and Fluorescence Microscopy of the Template-Removal Process

摘要

Zeolites and zeotype materials represent one of the most important types of heterogeneous catalysts widely used in the refining and petrochemical industry.[1]-[4] Although industrial zeolite-based catalysts contain mostly nano-to-micrometer-sized crystallites, larger zeolite single crystals with dimensions of hundreds of micrometers have proven to be indispensable as model materials for diffusion and reactivity studies.[5]-[9] It was established that these crystals often have complex structures consisting of several intergrown subunits.[10], [11] The way in which the building blocks are interconnected may severely affect intracrystalline transport properties or even make certain parts of the zeolite crystal completely inaccessible for the reactant molecules.[5] For example, the intergrowth structure of ZSM-5 crystals elucidated from electron diffraction, X-ray diffraction, and optical microscopy results has been discussed over the past 20 years.[11]-[14] Recently, Lehmann et al. visualized subunits of AlPO4-5 crystals by probing intracrystalline concentrations of absorbed methanol by interference microscopy.[15]