A novel nanoporous carbon membrane produced by carbonization of poly(vinylidene chloride) is described. The membrane separates gas mixtures by selective adsorption and surface diffusion of the more strongly adsorbed components. In particular, the membrane can very efficiently separate hydrocarbons from hydrogen from low-pressure gas streams. The method of preparation of the membrane and its characterization, pure and mixed gas permeabilities through the membrane, as well as an industrial application are reported.