Crystallization and spontaneous phase transformation of MTN-type zeolite with tetragonal symmetry

摘要

MTN-type zeolite with tetragonal symmetry was hydrothermally synthesized in a reactant system of Na2O-SiO2-NaF-H2O using N-ethyl-hexamethylenetetraammonium bromide as the template. A spontaneous phase transformation of the assynthesized zeolite at ambient temperature from tetragonal to cubic symmetry was investigated with polarized light microscopy, X-ray powder diffraction Si-29 magic angle spinning nuclear magnetic resonance, and differential scanning calorimetry. The results of the investigations indicate that the as-synthesized tetragonal MTN zeolite is a metastable phase. (C) 2002 Elsevier Science (USA). [References: 20]