Carbon composite membranes from Matrimid (R) and Kapton (R) polyimides forgas separation

The preparation and characteristics of supported carbon membranes from comm ercial polyimides are reported here. Carbon molecular sieve membranes (CMSM ) with asymmetric and symmetric structures have been obtained in only one c asting step by the phase inversion technique. The precursors were polyimide -type polymers available commercially: Allotherm(R) 610-16 (BASF) and Matri mid(R) 5218 (Ciba Specialty Chemicals). The preparation method involved coa ting of the macroporous carbon supports with a polymeric solution and subse quent gellation of the polymeric film by immersion in a coagulant bath. The carbon membranes were obtained by heat treatment (450-700 degrees C) of th e resulting devices under vacuum. The permeability and selectivity data ind icate that the resulting carbon membranes possess molecular sieve propertie s and that they are suitable for the separation of permanent gases of indus trial interest (O-2/N-2, CO2/CH4, CO2/N-2, etc.). Kapton(R) carbon membrane s are more permeable than those derived from Matrimid(R). The permeability and permselectivity measured at 25 degrees C for Kapton(R)-derived CMSM wer e: permeability (CO2) = 92 Barrer, permselectivity (CO2/CH4) = 16, permsele ctivity (CO2/N-2 = 9; permeability (O-2)=45 Barrer, permselectivity (O-2/N- 2)=4. By contrast, the materials obtained from Matrimid(R) are, in general, less permeable but more selective: permeability (CO2)=12 Barrer, permselec tivity (CO2/CH4)=33, permselectivity (CO2/N-2)=15; permeability (O-2)=5 Bar rer, permselectivity (O-2/N-2)=6. (C) 1999 Elsevier Science B.V. All rights reserved.