(551g) Molecular Layer Deposition Modified SAPO-34 Membranes on Ceramic Hollow Fibers for Separation of H2/N2 Mixtures at High Temperature and High Pressure

Zeolite membranes have drawn research interest in gas and liquid separations due to their well-defined pores and channel structure and high chemical, thermal and mechanical stability. In this study, SAPO-34 membranes were successfully synthesized on the outside of ceramic hollow fibers by secondary growth method. The influence of synthesis parameters, such as precursor composition, seed particle size, morphology, concentration and stabilizer concentration in the seed suspension, and seeding conditions, and of pore size of support, on the separation performance of SAPO-34 membranes was studied in detail. Results indicated that high quality SAPO-34 membranes with thickness of < 5 µm could be achieved by using high aspect ratio seeds. The as-synthesized membranes exhibited a high H₂ permeance of 2.9×10^-7 mol/(m²·s·Pa) and H₂/N₂ separation selectivity of 19 at 400 ^oC and pressure drop of 100 psig. To further increase the selectivity, a microporous Al₂O₃ coating was deposited on SAPO-34 membrane using molecular layer deposition (MLD). The microporous Al₂O₃/SAPO-34 membrane showed higher selectivity compared SAPO-34 membrane. The thickness of the MLD layer is being optimized for optimal permeance and selectivity of the membranes, which will be discussed in detail in the presentation. These high-quality membranes may be used for high purity H₂ production from decomposition of NH₃.