Browsing by Author "Rodrigues, Sandra C."
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Item Boehmite-phenolic resin carbon molecular sieve membranes-Permeation and adsorption studies(2014-11-01) Teixeira, Miguel; Rodrigues, Sandra C.; Campo, Marta; Pacheco Tanaka, David A.; Llosa Tanco, Margot A.; Madeira, Luís M.; Sousa, José M.; Mendes, Adélio; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOSComposite carbon molecular sieve membranes (c-CMSM) were prepared in a single dipping-drying-carbonization step from phenolic resin solutions (12.5-15wt.%) loaded with boehmite nanoparticles (0.5-1.2wt.%). A carbon matrix with well-dispersed Al2O3 nanowires was formed from the decomposition of the resin and dehydroxylation of boehmite. The effect of the carbon/Al2O3 ratio on the porous structure of the c-CMSM was accessed based on the pore size distribution and gas permeation toward N2, O2, CO2, He, H2, C3H6 and C3H8. c-CMSM with higher carbon/Al2O3 ratios had a more open porous structure, exhibiting higher permeabilities and lower permselectivities. c-CMSM performance was above the upper bound curves for polymeric membranes for several gas pairs, particularly for C3H6/C3H8 (permeability toward C3H6 of 420 barrer and permselectivity of 18.1 for a c-CMSM with carbon/Al2O3 ratio of 4.4).Unsupported films were also prepared (carbon/Al2O3 ratio 7.3) and crushed into small flakes. Equilibrium isotherms of H2, N2, O2, CO2, C3H8 and C3H6 at 293K were determined on these flakes to obtain the kinetic and adsorption selectivities toward gas pairs of interest; obtained adsorption and diffusion coefficients accurately predicted the permeabilities of all studied gases except CO2 (experimental and predicted permeabilities of 1148 and 154 barrer, respectively).Item Composite-alumina-carbon molecular sieve membranes prepared from novolac resin and boehmite. Part I: Preparation, characterization and gas permeation studies(2015-05-04) Llosa Tanco, Margot A.; Pacheco Tanaka, David A.; Rodrigues, Sandra C.; Texeira, Miguel; Mendes, Adélio; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOSAbstract 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.