Preparation of highly graphitized porous carbon and its ethane/ethylene separation performance

Efficient separation of ethane (C₂H₆) and ethylene (C₂H₄) is crucial for the preparation of polymer-grade C₂H₄, necessitating the development of highly selective and stable C₂H₆/C₂H₄ adsorbent. In this study, highly graphitized porous carbon, denoted as GC-800, was synthesized via room temperature polymerization followed by carbonization at 800 ºC using phenolic resin as the precursor and FeCl₃ as the iron source. VASP calculations confirmed higher binding energy between C₂H₆ molecules and graphitized porous carbon surfaces. The increase in graphitization degree effectively enhanced the adsorption capacity of porous carbon for C₂H₆, but the catalytic graphitization process of Fe at high temperatures could disrupt the microporous structure of porous carbon, thereby reducing the separation ability of C₂H₆/C₂H₄. By controlling the carbonization temperature, the graphitization degree and pore structure of the porous carbon were synergistically optimized. Raman spectra and XPS spectra revealed that GC-800 exhibited high graphitization degree, with a sp² C content as high as 73%. Low-temperature N₂ physical adsorption measurements estimated the specific surface area of GC-800 to be as high as 574 m²·g⁻¹. At 298 K and 1 bar, GC-800 exhibited an equilibrium adsorption capacity of 2.16 mmol·g⁻¹ for C₂H₆, with C₂H₆/C₂H₄ (1∶1 and 1∶9, v/v) IAST selectivity respectively reaching 2.4 and 3.8, significantly higher than those of most reported high-performance C₂H₆ selective adsorbents. Dynamic breakthrough experiments demonstrated that GC-800 could obtain high-purity C₂H₄ in a single step from a mixture of C₂H₆ and C₂H₄. Dynamic cycle tests confirmed the good cyclic stability of GC-800 exhibited good cyclic stability, which could efficiently separate C₂H₆/C₂H₄ even under humid conditions.