Molecular sieve properties of general-purpose carbon fibres

Molecular sieve properties of general-purpose carbon fibres (GPCFs) from different origins are studied. Selectivity of the materials for CO2 and CH4 separation and uptake of these gases are analysed and compared with a commercial pelleted carbon molecular sieve appropriate for this process. A set of four GPCFs, one of them commercially available, obtained from petroleum or coal tar pitches is used in this work. Kinetics of CO2 and CH4 uptake at different pressures and temperatures have been followed. The results obtained show that the GPCFs have a high selectivity to CO2, the kinetics of the process being very slow. The treatments, which comprise either the elimination of surface oxygen groups or controlled gasification, produce materials with a high selectivity and CO2 uptake and fast kinetics. In this sense, the general-purpose carbon fibres can have a performance as good as a commercial carbon molecular sieve. (C) 1998 Elsevier Science Ltd. All rights reserved.