Composite-alumina-carbon molecular sieve membranes prepared from novolac resin and boehmite. Part I: Preparation, characterization and gas permeation studies

Abstract Supported composite alumina-carbon molecular sieve membranes (c-CMSM) were prepared from in house prepared novolac phenolic resin loaded with boehmite nanoparticles in a single dipping-drying-carbonization step. A porous α-alumina tube support was dipped into a N-methyl-2-pyrrolidone solution containing polymerized novolac resin loaded with boehmite, subsequently dried at 100 C and carbonized at 500 C under nitrogen environment. The structure, morphology and performance of the membranes were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), carbon dioxide adsorption and permeation of N₂, O₂, He, H₂ and CO₂. SEM showed carbon membranes with a thin and very uniform layer with a thickness of ca. 3 μm CO₂ adsorption isotherms indicated that the produced carbon membranes presented a microporous structure. The c-CMSM exhibited good gas separation properties. The permselectivity surpass the Robeson upper bound for polymeric membranes, especially regarding ideal permselectivities of pairs H₂/N₂ = 117, and He/O₂ = 49. Aging effects were observed after membrane exposure to ambient air. However with a thermal treatment under nitrogen atmosphere the permeance of nitrogen increases.