A carbon molecular sieve membrane with a high gas permselectivity for perma
nent gas pairs (O-2-N-2, N-2-He, CO2-CH4) is obtained by carbonization of a
commercial polyimide (polyetherimide). The membrane is obtained in only on
e casting step, and it is constituted by a thin microporous carbon film of
around 3 mu m in thickness which is supported on a macroporous carbon subst
rate. (C) 1998 Elsevier Science B.V. All rights reserved.