Fast synthesis of thin Silicalite-1 zeolite membranes at low temperature

Abstract The preparation of zeolite membranes usually involves long hydrothermal synthesis at elevated temperature, which leads to issues like lengthy synthesis, high energy consumption, safety concern etc. It is desirable to prepare zeolite membranes at low temperature with short synthesis time. In this study, thin Silicalite-1 zeolite membranes were prepared in 4–6 h by conventional hydrothermal synthesis at ~373K. The use of ammonium hexafluorosilicate ((NH4)2SiF6), a highly reactive silica source, is the key to the ultrafast crystallization kinetics even at low temperature, which greatly increased productivity of membrane synthesis. The crystal growth rates of Silicalite-1 crystals and membranes were at least 10 times faster than using regular silica source. Hexane permporometry indicated the presence of low defect density in the membrane. High n-butane permeance of 4.3 × 10−7 mol m-2 s-1·Pa-1 and decent n-butane/i-butane selectivity of 17 were obtained on the Silicalite-1 membranes, which is comparable to the leading Silicalite-1 membranes. The fast synthesis of high performance Silicalite-1 membranes at benign condition greatly simplified membrane preparation and lowered membrane cost. This approach might be used for the synthesis of other types of all-silica zeolite membranes.