Pure, defect-free MEL type zeolites was synthesized by using 1-ethyl-6-azonia-spiro-[5,5]-undecane (EASU) as a structure directing agent. The absence of intergrowth with MFI-type structure, which usually occurs when tetrabutylammonium (TBA) is used as a SDA, was confirmed by the observation of the weak and sharp (110) reflection in the XRD pattern of the calcined pure silica sample, as well as by the Rietveld refinement of the synchrotron powder diffraction pattern. Evidences derived from a molecular modeling study supported the high specificity of EASU towards the crystallization of defect-free MEL.
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