Ag2O Nanoparticles Encapsulated in Ag-Exchanged LTA Zeolites for Highly Selective Separation of Ethylene/Ethane

Silver-modified LTA zeolites are validated to be one of the most efficient nanomaterials applied in adsorptive separation, which is an energy-efficient alternative to the state-of-the-art cryogenic distillation for ethylene and ethane separation. Here, three representative LTA zeolites, Ag modifications via different methods including ion-exchange, mechanical mixing, and acid leaching, are systematically explored by X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, H2 temperature-programming reduction, and ultraviolet–visible spectroscopy with the assistance of Grand Canonical Monte Carlo simulations to identify the location of various Ag species in the LTA zeolite and thus to understand the mechanism of promoted separation performance in nature. The performance of these zeolites for the separation of ethylene/ethane is validated via ideal adsorbed solution theory and breakthrough experiments under ambient conditions. It is confirmed that Ag+ can afford selective binding of ethylene via π-complexation. Ag2O nanoparticles encapsulated in the zeolitic channels narrow the pore diameters to the suitable size, excluding ethane via molecular sieving. The synergistic effect of π-complexation and molecular sieving from Ag+ and Ag2O nanoparticles in the zeolitic channels triggers highly selective adsorption of ethylene over ethane.