Synthesis of SUZ-4 zeolite by a dry gel conversion method

Abstract

SUZ-4 zeolite was synthesized by the dry gel conversion (DGC) process with water vapor as gas phase, and characterized by XRD, SEM and N2 adsorption. The dry gel was prepared with the assistance of a small amount of crystalline seed and organic template tetraethylammonium hydroxide (TEAOH). Molar ratios of SiO2/Al2O3, KOH/SiO2, TEAOH/SiO2 and H2O/SiO2, amounts of seed and dry gel, types of silica sources, and crystallization temperature and time, were changed to optimize synthesis conditions. The results show that the DGC method leads to formation of SUZ-4 zeolite in a broad range of crystallization temperature 120–180 °C. Under the optimal conditions, i.e., SiO2/Al2O3 = 22.5, KOH/SiO2 = 0.44, TEAOH/SiO2 = 0.044, H2O/SiO2 = 22.2, seed amount = 0.1 wt%, fumed silica as the silica source, 160 °C and 5 days, SUZ-4 zeolite is obtained with a high crystallinity. Compared to hydrothermal synthesis, the present DGC approach employs far less amount of organic template and allows using inert fumed silica as silica source, producing smaller rod-like SUZ-4 zeolite crystals.