Low-corrosion preparation of porous carbons with narrow micropores for efficient separation of CH4/N2

This study developed a low-corrosive method for preparing porous carbons with a concentrated pore distribution for CH4/N2 separation. Pine chips were impregnated with H3PO4 and activated with CO2 or C6H5K3O7 to obtain microporous carbon. The differences in physical structure and surface chemistry of the porous carbons were analyzed to explore their impact on the CH4 adsorption properties. The carbonization mechanism of pine chips was preliminarily explored. The results showed that H3PO4 impregnation caused the pine chips to swell and form low molecular compounds, which promoted deeper penetration of C6H5K3O7 into the carbon matrix. Further etching of K+ promoted the formation of narrow microporous structures and introduced extra oxygen groups on the material surface. The CH4 adsorption performance of porous carbon is closely related to the volume of ultramicropores between 0.45-0.7nm, specific oxygen groups and specific surface area. Correspondingly, owing to its narrow pore size distribution, higher specific surface area (1341 m2/g) and greater microporous volume (0.57 cm3/g), HCK5.5 (C6H5K3O7 addition ratio of 5.5) exhibited an impressive adsorption capacity of 1.77mol/g for CH4 at 298K, surpassing that of most MOF and carbon materials. Moreover, the prepared adsorbents exhibited reasonable heat of adsorption and excellent regenerability. This study provides new insights into the development of narrow microporous carbon materials for CH4/N2 separation.