Balancing the Kinetic and Thermodynamic Synergetic Effect of Doped Carbon Molecular Sieves for Selective Separation of C2H4/C2H6

Abstract

AbstractSelective separation of ethylene and ethane (C2H4/C2H6) is a formidable challenge due to their close molecular size and boiling point. Compared to industry‐used cryogenic distillation, adsorption separation would offer a more energy‐efficient solution when an efficient adsorbent is available. Herein, a class of C2H4/C2H6 separation adsorbents, doped carbon molecular sieves (d‐CMSs) is reported which are prepared from the polymerization and subsequent carbonization of resorcinol, m‐phenylenediamine, and formaldehyde in ethanol solution. The study demonstrated that the polymer precursor themselves can be a versatile platform for modifying the pore structure and surface functional groups of their derived d‐CMSs. The high proportion of pores centered at 3.5 Å in d‐CMSs contributes significantly to achieving a superior kinetic selectivity of 205 for C2H4/C2H6 separation. The generated pyrrolic‐N and pyridinic‐N functional sites in d‐CMSs contribute to a remarkable elevation of Henry selectivity to 135 due to the enhancement of the surface polarity in d‐CMSs. By balancing the synergistic effects of kinetics and thermodynamics, d‐CMSs achieve efficient separation of C2H4/C2H6. Polymer‐grade C2H4 of 99.71% purity can be achieved with 75% recovery using the devised d‐CMSs as reflected in a two‐bed vacuum swing adsorption simulation.