Carbon molecular sieve membranes (CMSM) were prepared on a-alumina supports by carbonization of a resorcinol-formaldehyde resin loaded with boehmite. Two series of carbon membranes produced at 500 degrees C and 550 degrees C carbonization end temperatures were prepared. The influence of the carbonization end temperature on the structure, morphology and performance of the membranes was examined by scanning electron microscopy, thermogravimetric analysis, CO2 adsorption and permeation to N-2, O-2, He, H-2 and CO2 at temperatures from 25 degrees C to 120 degrees C. SEM photographs showed carbon membranes with a thin and very uniform layer and a thickness of ca. 3 mu m. Carbon dioxide adsorption isotherms revealed that all the produced carbon membranes have a well-developed microporous structure. Nevertheless, the membranes carbonized at 550 degrees C have more ultramicropores and a narrower pore size distribution. The permselectivity of CMSM prepared at this temperature surpasses the Robeson upper bound for polymeric membranes, especially regarding ideal selectivities of pairs O-2/N-2 (O-2 permeation rate: 9.85 x 10(-10) mol m(-2) s-1 Pa-1 and ideal selectivity: > 11.5), H-2/N-2 (H-2 permeation rate: 5.04 x 10(-8) mol m(-2) s-1 Pa-1 and ideal selectivity: > 586) and He/N-2 (He permeation rate: 4.68 x 10(-8) mol m(-2) s-1 Pa-1 and ideal selectivity: > 544). (C) 2014 Elsevier B.V. All rights reserved