Boehmite-Phenolic Resin Carbon Molecular Sieve Membranes - Permeation and Adsorption Studies

Abstract

Composite carbon molecular sieve membranes (c-CMSM) were prepared in a single dipping-drying-carbonizationstep from phenolic resin solutions (12.5-15 wt.%) loaded with boehmite nanoparticles (0.5-1.2 wt.%). A carbon matrixwith well-dispersed Al2O3 nanowires was formed from the decomposition of the resin and dehydroxylation ofboehmite. The effect of the carbon/Al2O3 ratio on the porous structure of the c-CMSM was accessed based on the poresize distribution and gas permeation toward N2, O2, CO2, He, H2, C3H6 and C3H8. c-CMSM with higher carbon/Al2O3ratios had a more open porous structure, exhibiting higher permeabilities and lower permselectivities. c-CMSMperformance was above the upper bound curves for polymeric membranes for several gas pairs, particularly forC3H6/C3H8 (permeability toward C3H6 of 420 barrer and permselectivity of 18.1 for a c-CMSM with carbon/Al2O3 ratioof 4.4).Unsupported films were also prepared (carbon/Al2O3 ratio 7.3) and crushed into small flakes. Equilibrium isothermsof H2, N2, O2, CO2, C3H8 and C3H6 at 293 K were determined on these flakes to obtain the kinetic and adsorptionselectivities toward gas pairs of interest; obtained adsorption and diffusion coefficients accurately predicted thepermeabilities of all studied gases except CO2 (experimental and predicted permeabilities of 1148 and 154 barrer,respectively).