(491d) Ultra-Selective Defect-Free Interfacially Polymerized Molecular Sieve Thin-Film Composite Membranes

Aromatic polyamide thin-film composites made by interfacial polymerization are state-of-the-art membranes for reverse osmosis and nanofiltration. These membranes contain nano-defects that have essentially little effect on their performance for aqueous applications but reduce their selectivity for gas separation applications to very low Knudsen diffusion-based values. In this work, inexpensive high-performance gas separation membranes were fabricated by modifying the commercially successful reverse osmosis interfacial polymerization membrane production method. The effects of fabrication variables on the morphologies of the thin-film composite membranes optimized for gas separation applications will be presented. Defect-free thin-film composite membranes demonstrated unprecedented mixed-gas H₂/CO₂ selectivity of ≈ 50 at 140 °C with H₂ permeance of 350 GPU (10^-6 cm³(STP cm^-2 s^-1 cmHg^-1), surpassing the hydrogen/carbon dioxide permeance/selectivity upper bound of all known polymer membranes by a wide margin. The combination of exceptional separation performance and low manufacturing cost makes them excellent candidates for cost-effective hydrogen purification from steam cracking and similar processes. Permeance and selectivity measurements imply an ultrathin polyamide layer with apparent thickness of ≈ 10-20 nm. Potential use of the membranes in challenging reverse osmosis applications will be proposed.