Screening of Zeolite Molecular Sieves for Ne/He Separation at Liquid Nitrogen Temperature: Adsorption Behavior, Thermodynamics, and Practical Feasibility

To address the challenge of efficiently separating low concentrations of neon (Ne) from helium (He) in natural gas sources, we examine a series of zeolite frameworks with various structures for their Ne/He adsorption behaviors at liquid nitrogen temperature. Ne and He adsorption characteristics are assessed for the adsorption thermodynamics using isotherm models (Langmuir, Freundlich, Freundlich-Langmuir, and Virial), and dynamic breakthrough experiments to evaluate the feasibility of separating Ne/He gas mixtures under practical conditions. Molecular dynamics simulation calculations are performed to explain the nature of Ne adsorption within the porosities of different zeolite frameworks and identify the prevailing retention mechanisms. Our data identify zeolite SSZ-13 as the optimal material for Ne/He separation at 77 K, achieving the highest Ne adsorption capacity (3.68 mmol g⁻¹ at 101 KPa) and exceptional IAST selectivity of Ne/He among the investigated frameworks under various mixed gas conditions. The exceptional Ne/He separation performance of SSZ-13 is likely attributed to its chabazite (CHA) topology, which provides synergistic confinement effects through its dual-cage architecture, preferentially retaining Ne while allowing He to pass through. Dynamic tests confirm the practical viability of SSZ-13 and ZSM-5, both delivering > 99.999% He purity with stable recyclability over five cycles.