High-silica MOR type zeolite self-transformed from dry aluminosilicate gel in OSAs-free and fluoride-free reactant system

An environmental friendly method for the synthesis of high-silica large-port MOR type zeolite was carried out in organic structure-directing agents (OSAs)-free and fluoride-free reactant system by dry aluminosilicate gel self-transformation (DGST). Identifications of the obtained products with powder X-ray diffraction (XRD) indicate that the molar ratio of silica to alumina (SAR) and the alkalinity in the starting dry gel play essential roles in the crystallization of the zeolite with pure phase. The gel composition region for the zeolite crystallization was investigated and expressed with diagram in detail. The as-synthesized MOR zeolite with SAR up to 30 prepared from DGST with optimum gel compositions possesses a morphology of rod shape single crystals with the size of 1–3 × 0.2–0.5 μm, and perfect framework and channel system with 0.18 cm3/g of micropore volume, 378 m2/g of BET surface area and 9.0 wt.% of benzene adsorption capacity characterized by scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), selected-area electron diffraction (SAED), 27Al magic-angle spinning nuclear magnetic resonance (MAS NMR), and adsorption determination. The reason for that the as-synthesized pure MOR zeolite possesses higher SAR is discussed. H-form high silica MOR zeolite with SAR of 30 synthesized with DGST presents more excellent stability in steam at 1073 K and stronger solid acidity in comparison with that of dealuminated commercial MOR zeolite sample with SAR of 29.