| Abstract
| - As-synthesized MCM-49 is a three-dimensional (3D) microporousaluminosilicate zeolite with the MCM-22framework topology. It is formed hydrothermally in a reaction geland is the first example of a zeolite withthis topology to be produced by direct synthesis, in contrast with theconventional procedure in which aprecursor is formed first and is then calcined. Whenhexamethyleneimine (HMI) is used as the directingagent, a SiO2/Al2O3 ratio of theframework as low as 17/1 can be achieved. X-ray powder diffraction(XRD),temperature programmed base desorption (TPBD) experiments, andmultinuclear NMR analyses of this zeoliteand others in this series (viz., calcined MCM-22 and itsprecursor) provide new insights into the novelty ofthis class of materials. TPBD and 13C NMR experiments,for example, provide experimental evidence thatsupport the coexistence of different dual pore systems within both theMCM-22 precursor and MCM-49.The 27Al MAS NMR spectra of MCM-22 and calcinedMCM-49 exhibit three distinct Td resonances, afeaturenot previously observed for any other zeolite. And finally,aluminum enrichment of the T1−O1−T1 bridgein MCM-49 is postulated on the basis of the length of its unit cellc-parameter.
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