Hydrogen-permselective carbon membranes were prepared by a vapor-phase synthesis using furfuryl alcohol as a carbon source. Their pore sizes were evaluated from the molecular sieving properties by single gas permeations of H-2, CO2, CH4 and CF4. The pore size of the carbon membranes was increased by a post-synthesis activation using various gases and vapors such as H-2, CO2, O-2 and steam. The activation using H2 was the most effective for improving both the H-2 permeance and permselectivity because the molecular size of H-2 is smaller than the pore size of the carbon membrane and can react with the inner surface of the carbon membrane. After the activation using H-2 at 973 K, the pore size of the carbon membrane was increased from 0.30 to 0.45 nm, and the permeance of H-2 was increased from 3.6 x 10(-9) to 1.6 x 10(-8) mol m(-2) s(-1) Pa-1. The activated carbon membrane was used in a membrane reactor for dehydrogenation of methylcyclohexane and showed potential for application in the dehydrogenation of chemical hydrides in membrane reactors. (C) 2013 Elsevier B.V. All rights reserved.