Silver ZK-5 zeolites for selective ethylene/ethane separation

Abstract The development of efficient adsorbents for olefin/paraffin separation has attracted great attention, because an alternative energy-efficient technology is required to move away from the energy intensive cryogenic distillation processes. Here, we have prepared two silver-exchanged ZK-5 (Ag-ZK-5) zeolites with low (2.9) and high (3.7) Si/Al ratios, as well as various other cation-exchanged forms, for ethylene/ethane separation and compared their separation properties with those of zeolites Na-, Ca- and Ag-A with Si/Al = 1.0 and Ag-UZM-9 with Si/Al = 3.7. Among the zeolite adsorbents tested here, Ag-ZK-5 with Si/Al = 3.7 has the highest ethylene/ethane selectivity (2.54) at 298 K in vacuum-swing adsorption mode, together with fast adsorption kinetics. While the breakthrough results hint at its applicability in concentrated ethylene/ethane streams, the outstanding performance of this Ag-ZK-5 for ethylene/ethane separation appears to be due to a combination of its unique framework topology and composition (Al content) which can stabilize monovalent silver ions.