Single-step ethylene purification from ternary C2 hydrocarbon mixtures in a scalable metal–organic framework

Abstract

Single-step purification of the ternary C2 hydrocarbon mixture to produce ethylene (C2H4) directly using adsorption-based technologies is desirable for reducing large energy consumption. However, it is challenging to develop an appropriate adsorbent, having preferential adsorption characteristics toward ethane (C2H6) and acetylene (C2H2) rather than C2H4 coupled with high adsorption capacity owing to their similar physicochemical properties. Herein, we present a highly stable, cheap, and scalable CAU-23 adsorbent, which enables single-step production of high-purity C2H4 (>99.9%) from the ternary C2 hydrocarbon mixture. CAU-23 exhibited higher uptake capacity of C2H6 (4.0 mmol g−1) and C2H2 (4.7 mmol g−1) compared to that of C2H4 (3.8 mmol g−1). Further, it showed the reasonable selectivity for both C2H6/C2H4 (1.54) and C2H2/C2H4 (1.5) with an equimolar binary mixture, indicating that the separation performance of CAU-23 is comparable to the benchmark porous materials for separating C2 ternary gas mixture. The breakthrough experiments demonstrated its capability to produce high-purity C2H4 (>99.9%) with various C2H6/C2H4/C2H2 compositions at 298 K and 1 bar with high recyclability. The origin of the separation performance was further explored by using computational simulations of the grand canonical Monte Carlo (GCMC) and density functional theory (DFT).