Cellulose-based carbon membranes for gas separations - unraveling structural parameters and surface chemistry for superior separation performance

Carbon molecular sieve membranes were prepared from the carbonization of a cellulose-based polymeric precursor doped with urea. The addition of urea to the cellulose precursor induces an increase in structural disorder and an increase in pore volume inside the structure of prepared membranes. This unique preparation procedure proved to be an extremely effective method for tuning the pore size of carbon membranes to the desired separations. Urea acts as a pore-forming agent that allows the fabrication of carbon membranes with high porosity. The addition of 2.8 wt% of urea doubled the permeability of the prepared carbon membrane to hydrogen. In addition, a permeability to oxygen of 333 barrer was obtained, without impairing the selectivity. The proposed preparation procedure is compatible with industrial production and scaling, hopefully making carbon membranes a viable solution to produce oxygen-enriched air, recovering of hydrogen from hydrocarbon streams and carbon dioxide removal from natural gas/biogas.