Preparation of Zeolite ZSM-5 Membranes by In-Situ Crystallization on Porous α-Al_2O_3

Zeolite ZSM-5 membranes were grown on porous α-Al_2O_3 disks by in-situ hydrothermal synthesis at 175 "C. The zeolite layers were formed on the bottom face of disks placed horizontally near the air-liquid interface of clear synthesis solutions. Extensive experimentation was carried out to find compositions that gave continuous polycrystalline films. The films grown with the optimized composition were about 10 µm thick and consisted of well-intergrown crystals of about 2 µm size. Pure gas permeation measurements of the most successful preparation yielded hydrogen:isobutane and n-butane:isobutane ratios of 151 and 18 at room temperature and 54 and 31 at 185 °C, respectively.