Cellulose-based carbon hollow fiber membranes for high-pressure mixed gas separations of CO2/CH4 and CO2/N2

[Display omitted] •Carbon molecular sieve hollow fiber membrane was prepared from cellulose precursor.•The CHFM present high mixture CO2/CH4 selectivity of 150 at 10% v/v CO2.•The achieved CO2/CH4 separations surpass the 2008 Robeson upper bound.•Process simulation indicates our system feasible to produce 96% methane.•The developed CHFMs present a potential applicability in NG sweetening process. Carbonized cellulose -based hollow fiber membranes were prepared by dry-wet spinning phase inversion method, followed by carbonization and evaluated in terms of gas separation performance for CO2/N2 and CO2/CH4 mixtures, under flow conditions. Permeability and real selectivity were measured for both mentioned mixtures, in a temperature range of 25 °C to 60 °C, a differential pressure range of 8 bar(a) to 20 bar(a) and a CO2 concentration range from 5% v/v to 15% v/v. The highest yielding mixture selectivity values were 42 for CO2/N2 at 10% v/v CO2, 25 °C & 8 bar(a) and around 150 for CO2/CH4 at the same conditions, whereas the respective CO2 permeabilities were 110 and 45 Barrer. Additionally, experiments of varying head pressure, while maintaining differential pressure, transmembrane pressure, at 8 bar(a), have revealed that CO2/N2 separation factor can be further enhanced with real selectivity being raised to 55 and permeability to 180 at 20 bar head pressure. The same approach had negligible effect on CO2/CH4 separation. This is an important finding by taking into consideration that natural gas treatment, i.e. sweetening and purification processes, is energetically and economically convenient if it takes place under the conditions, where the NG stream is extracted from the wells, or after a decompression. Moreover, Process simulation indicates that a two-stage system using the developed carbon membranes is technologically feasible to produce 96% methane with a low methane loss of