Preparation and Characterization of Free-Standing Composite Cellulose-Based Carbon Molecular Sieve Membranes

Abstract

Abstract: Carbon membranes with excellent strength and mechanical stability were prepared using a cellulose precursor regenerated from an ionic liquid solution with a low loading of boehmite ceramic nanoparticles, ca. 0.1 wt. %. The precursor films show an asymmetrical structure while, after carbonization, the corresponding carbon molecular sieve membranes (c-CMSM) show a dense structure with a uniform thickness of ca. 22 mm. The c-CMSM exhibited excellent separation performance, well above the Robeson Upper Bound. The permeability of the c-CMSM to hydrogen increased from 300 to 530 barrer and the H₂/CH₄ permselectivity increased to 473, after adding boehmite nanoparticles. Boehmite nanoparticles act as a microporosity-forming agent without compromising the width of the ultramicropores. The prepared c-CMSM is extremely promising for several applications, namely for hydrogen recovery from methane – H₂/CH₄ (Robeson index: =13.5); biogas upgrading – CO₂/CH₄ (=6.5); CO₂ removal from combustion flue gas – CO₂/N₂ (=1.7); and hydrogen recovery from ammonia processes – H₂/N₂ (=4.8).