Versatile Use of the Small Tubular Reactor and Introduction of a Novel Design Reactor for Rapid Synthesis of Silicalite-1 Membranes

The rapid synthesis of high-performance silicalite-1 membranes was systematically investigated by examining the effects of seed size, solution volume, and reactor configuration on membrane growth, microstructure, and gas separation performance. Silicalite-1 seeds (~100 nm and ~1 µm) were dip-coated onto capillary α-alumina supports, followed by secondary growth under controlled conditions. Small seeds (~100 nm) produced high nucleation density, uniform intergrowth, and defect-free membranes, yielding consistently high ideal separation factor for H₂/SF₆ (181-295) and low SF₆ permeance (~10^-9 mol m^-2 s^-1 Pa^-1) after only 45 min of synthesis. In contrast, larger seeds (~1 µm) enabled faster growth but resulted in less uniform layers with inferior selectivity. Furthermore, a novel reactor design with enhanced heat transfer enabled the rapid silicalite-1 membrane synthesis on conventional large-diameter tubular supports, producing well-intergrown and uniform membranes with high H₂ permeance (4.7 × 10^-6 mol m^-2 s^-1 Pa^-1) and high ideal separation factors of up to 349 for H₂/SF₆ and 223 for N₂/SF₆. Overall, this study demonstrates that optimization of seed properties, synthesis parameters, and reactor design enables rapid and scalable fabrication of silicalite-1 membranes with robust molecular sieving performance, highlighting their strong potential for SF₆ purification applications.