Composite carbon molecular sieve membranes (c-CMSM) were prepared from phenolic resin loaded with boehmite by a single dipping-drying-pyrolysis step. The composite membrane was analyzed by scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction, thermogravimetric analysis, mercury porosimetry, CO2 adsorption and permeation experiments. It was produced a 2 μm thick composite uniform layer on top of a α-Al2O3 support. The composite top layer exhibited nanowires of Al2O3 1-2 nm thick and 10-30 nm long well dispersed in a microporous carbon matrix. The micropores network accounted for 63% of the total pore volume (DR isotherm). The c-CMSM exhibited ideal O2/N2 and C3H6/C 3H8 permselectivities of 5 and 15, respectively. The performance of the c-CMSM for pair C3H6/C 3H8 was above the upper bound curve for polymeric membranes, making it a promising vehicle for olefin purification. © 2011 Elsevier Ltd. All rights reserved.