Unraveling the separation mechanisms of the LTA zeolite depending on the regulated particle size and pore structure for efficient ethylene/ethane separation

Abstract

As an alternative to conventional cryogenic distillation, LTA zeolites act as cost-effective adsorbents for the adsorptive separation of ethylene and ethane. In this approach, the thermodynamic and kinetic separation of ethylene and ethane by LTA zeolites with regulated particle sizes and pore structures has been studied. Herein, LTA zeolites, with different particle sizes ranging from 0.82 μm to 4.96 μm and a pore diameter distribution concentrated around 4.16–5.07 Å, were prepared using the hydrothermal method followed by an ion-exchange procedure. The results indicated that variation of the zeolitic particle size and the Ca²⁺ exchange rate has a great influence on the separation process, including the selectivity of C₂H₄ and the breakthrough time intervals of C₂H₄ and C₂H₆. Several issues, including the intracrystalline diffusion, accessibility of active sites, reinforced interaction between adsorbents and adsorbates, and the confined space in the zeolitic channels, were investigated to explain the altered nature of the separation performance. The optimized separation performance was achieved using LTA zeolites with a particle size of 0.82 μm or with an ion-exchange rate of 69.13% and a pore diameter distribution of 4.94 Å.