Template-free synthesis of intergrown T zeolite with high CH4/N2 selectivity

Abstract

Although zeolite adsorbents are widely used for gas separation, current studies predominantly focus on single-phase topological structure. Herein, an intergrowth T zeolite with ERI and OFF topologies was synthesized in a template-free system, and the results showed the CH₄ adsorption capacity and CH₄/N₂ selectivity were 34.4 cm³/g and 5.3 (298 K, 1 bar), respectively. The exceptional performance was attributed to its high microporosity and the 6-member ring (6-MR) structure at the intergrowth interface, which synergistically optimize the distribution of adsorption sites, as evidenced by density functional theory (DFT) calculations. Breakthrough experiments demonstrated that intergrowth T zeolite can effectively separate CH₄/N₂ mixtures (50/50 and 20/80; v/v) with actual separation times of 7.0 min and 10.4 min. Furthermore, two-bed six-step pressure swing adsorption (PSA) simulations further indicated that 20 % of the pristine CH₄ could be enriched to over 50 %, with a recovery rate of 87 %, demonstrating significant potential for upgrading low-concentration coal-bed methane.