Preparation and characterization of carbon molecular sieve membranes based on resorcinol-formaldehyde resin

Abstract

Carbon molecular sieve membranes (CMSM) were prepared on α-alumina supports by carbonization of aresorcinol-formaldehyde resin loaded with boehmite. Two series of carbon membranes produced at500 1C and 550 1C carbonization end temperatures were prepared. The influence of the carbonizationend temperature on the structure, morphology and performance of the membranes was examined byscanning electron microscopy, thermogravimetric analysis, CO2 adsorption and permeation to N2, O2, He,H2 and CO2 at temperatures from 25 1C to 120 1C. SEM photographs showed carbon membranes with athin and very uniform layer and a thickness of ca. 3 mm. Carbon dioxide adsorption isotherms revealedthat all the produced carbon membranes have a well-developed microporous structure. Nevertheless, themembranes carbonized at 550 1C have more ultramicropores and a narrower pore size distribution.The permselectivity of CMSM prepared at this temperature surpasses the Robeson upper bound forpolymeric membranes, especially regarding ideal selectivities of pairs O2/N2 (O2 permeation rate: 9.85 1010 mol m2 s1 Pa1 and ideal selectivity: 411.5), H2/N2 (H2 permeation rate: 5.04 108 mol m2 s1 Pa1 and ideal selectivity: 4586) and He/N2 (He permeation rate: 4.68 108 mol m2 s1 Pa1 and ideal selectivity: 4544).