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New zeolite topologies based on intergrowths of FAU/EMT systems

Abstract:

The controlled synthesis of intergrowths of zeolites FAU and EMT was carried out by the mixture of the organic structure-directing agent (SDA) 15-Crown-5 (T1) and 18-Crown-6 (T2) in different proportions (T1/T2 = 25%, 50% and 75%), using T/Al2O3 ratios of 0.3 and 0.7, n-heptane and m-xylene catalytic reactions were used as model reactions for elucidating the pore and cage size of the solids. The samples were characterized by the following techniques XRD, FTIR, HRSEM, STM and EDX, N2 adsorption and TPD-NH3. The FAU samples were formed by octahedral submicrometric crystallites, EMT samples have hexagonal plate morphology of 2-5 μm. The intergrowth crystals are micrometric hexagonal plates through whose hexagonal faces intergrow the octahedral crystallites of FAU. The intergrowth proportions obtained were evaluated by comparison of the experimental XRD patterns with the simulated patterns using the DiFFaX computing program. The intergrowth proportion obtained depends on the molar ratio of template/Al2O3 and the relative proportion of SDA used in the gel. For a SDA proportion T1/T2 = 50% and a T/Al2O3 = 0.70, an intergrowth proportion 50% of FAU and 50% of EMT was obtained, with a stacking arrangement of clusters. When using the same T1/T2 but T/Al2O3 = 0.30, the intergrowth proportion was 12% of FAU and 88% of EMT. © 2006 Elsevier Inc. All rights reserved.