Ethane-selective aluminium-based metal-organic frameworks for separation of ethane/ethylene gas mixture

Abstract

Selective ethane adsorption from an ethane (C$_2$H$_6$)/ethylene (C$_2$H$_4$) mixture has emerged as a promising alternative to energy‐intensive cryogenic distillation for obtaining high‐purity ethylene. To develop a cost‐effective adsorption process, adsorbents that exhibit high adsorption capacity and high selectivity toward C$_2$H$_6$ are required. Therefore, understanding the correlation between the framework structures and their C$_2$H$_6$/C$_2$H$_4$ separation performance is important for the development of advanced adsorbent materials. In this study, various Al-based Metal-organic frameworks (MOFs), such as MIL-53 isomorphs, CAU-10 isomorphs, and CAU-3-NDCA were prepared using Al metal ions and various organic linkers to investigate the effect of pore structure and surface functionality in separation performance of C$_2$H$_6$/C$_2$H$_4$ mixture gas. The characterization of adsorbents and their C$_2$H$_6$/C$_2$H$_4$ separation performances of the adsorbents were rigorously investigated by combining single‐component gas adsorption, ideal adsorbed solution theory calculation, dynamic breakthrough experiment for mixture gas, and molecular simulations, including Monte Carlo simulation and density functional theory calculation. As results, all Al-based MOFs displayed the ethane-selective adsorption. For the ethane/ethylene separation performance on the basis of framework structure, the highest separation performance was observed in MIL-53-NDCA among the MIL-53 isomorphs, and in KMF-2 among the CAU-10 isomorphs. In case of CAU-3-NDCA, it exhibited the low separation performance at 1 bar, however, the enhanced separation performance was observed at high pressure over 7 bar.