Preparation and separation properties of LTA membranes by using 3-aminopropyltriethoxysilane as covalent linker

A novel synthesis strategy was developed for the seeding-free preparation of dense LTA zeolite membranes by using 3-aminopropyltriethoxysilane as covalent linker between zeolite membrane and porous Al₂O₃ support. In a first step, the ethoxy groups of the 3-aminopropyltriethoxysilane react with surface hydroxy groups of the support. In a second step, the 3-aminopropylsilyl groups react with silanols of the zeolite crystals, leading to a "bridge" between the growing LTA zeolite membrane and the support being built to anchor the LTA zeolite layer onto the support. The SEM image and XRD indicate that a dense and pure LTA zeolite membrane with a thickness of about 3.5 μm can be formed on the α-Al₂O₃ support, and no cracks, pinholes or other defects are visible. The LTA zeolite membrane displays good molecular sieving performance. For binary mixtures at 20 °C, the separation factors of H₂/CH₄, H₂/N₂, H₂/O₂ and H₂/CO₂ are 3.6, 4.2, 4.4 and 5.5, respectively, which are higher than the corresponding value of Knudsen diffusion. Moreover, relative high H₂ permeances of about 3.0 × 10^-7 mol m^-2 s^-1 Pa^-1 can be obtained.