Synthesis of ordered cubic mesoporous ZrMCM-48 molecular sieve with aid of fluoride ions

摘要

Using cetyltrimethyl ammonium bromide (CTAB) as the template and tetraethyl orthosilicate (TEOS) as silica source, ordered cubic mesoporous ZrMCM-48 molecular sieves were synthesized by addition of sodium fluoride in hydrothermal crystallization process. The structure and property of the calcined sample were characterized by XRD, TEM, XPS, and N_2 physical adsorption, respectively. The effect of crystallization time, crystallization temperature and F-/Si molar ratio on synthesis process of sample was systematically investigated. Also, the different molar ratios of Si/Zr on textural properties of ZrMCM-48 samples were also evaluated. The results show that the optimum synthesis conditions of cubic ZrMCM-48 sample are the following: crystallization temperature is 120°C, crystallization time is 24h and F-/Si ratio is 0.1. A small amount substitution of Zr ions for Si~(4+) in the framework of MCM-48 did not significantly change the textural properties while the higher Zr content incorporated leads to decrease of the surface area and deterioration of structural regularity.