Carbon membranes from cellulose: Synthesis, performance and regeneration

Cellulose hydrolysis with trifluoroacetic acid (TFA), that is gentle enough to preserve the monosaccharides, provided an anticipative route to carbon membrane formation. Increasing the hydrolysis time, resulted in reduced weight loss during carbonization, and better separation performance for selected gas pairs. The permeability of N2, H2, CH4, O2, and CO2 is reported for carbon membranes obtained from wood pulp hydrolyzed to different extents, as well as for carbon membranes obtained from different heating protocols (single gas tests at 30 °C and 2 bar). A simple, energy effective and rapid regeneration method for membranes that are conductors or semi-conductors has been developed: when a low voltage, direct current was applied on an iron-doped carbon, enhanced permeation rates were immediately observed. The permeability increase depends on several factors, including gas critical temperature and current size. Electrothermal regeneration may also be applied on-stream, avoiding process interruption or an extra set of membranes. The method can be used for a continuous process, and not only for batchwise regeneration (e.g. activated carbon).