Preparation of supported carbon molecular sieve membranes Original Research Article

Carbon molecular sieve membranes were prepared by carbonization of a polymeric film supported on a macroporous carbon substrate. Disk-shaped macroporous carbon supports (35 mm in diameter and 2.5 mm in thickness) were obtained by carbonization of fine particles of graphite blended with a phenolic resin. The polymeric precursor of the selective carbon film was a polyamic acid commercially available in solution that after imidization led to formation of BPDA-pPDA polyimide. The support coated with the polymeric solution was heated following the sequence: (i) drying at 150°C during 1 h in air (heating rate: 3°C/min); (ii) imidization under vacuum at 380°C (heating rate: 1°C/min); (iii) carbonization under vacuum at temperatures ranging between 550°C and 700°C (heating rate: 0.5°C/min). This procedure provided one-coat membranes. It was repeated to produce two- and three-coat carbon membranes. At 25°C the resulting carbon membranes showed selectivity O2/N2 of 14 and He/N2 of 136 and permeation rate of pure He and O2 of 27.2×10−10 and 2.8×10−10 mol/m2 s Pa, respectively.