Recent advances in zeolite-based adsorbents for enhanced CH₄/N₂/CO₂ separation in coalbed methane

Coalbed methane has attracted significant attention due to its potential for comprehensive utilization and the imperative need to control the emissions of the potent greenhouse gas methane. Pressure-swing adsorption separation is the most feasible gas enrichment technique, and zeolites show remarkable potential in the selective separation of CH₄, N₂, and CO₂ from coalbed methane due to their pore regularity and homogeneity, high specific surface area, large pore volume, and strong polarity. ETS-4, SAPO-18 and SAPO-34 exhibit N₂/CH₄ selectivities up to 26, 15 and 12, respectively, while ZK-5, zeolite A, X, Y, ZSM-5 and silicalite-1 deliver CH₄/N₂ selectivities up to 11.8 (Ag-ZK-5) and adsorption capacities of 1.2–4.0 mmol g⁻¹ CH₄ at 298 K and 0.1–0.3 MPa. Eight-membered-ring zeolites such as Li-SSZ-13, NaMg-GIS, SAPO-17 and K-MER achieve CO₂/N₂ selectivities of 310, 132, 276 and 85, respectively, with CO₂ adsorption capacities of 1.3–4.5 mmol g⁻¹ at 298 K and 0.1 MPa. A comprehensive review of recent advances in zeolites synthesis, modification techniques and adsorption kinetics is presented to elucidate the factors responsible for the increased CH₄ adsorption capacity and selectivity of different zeolite types. Furthermore, this review proposes the prevailing challenges and offers our personal perspectives for the application of zeolite in coalbed methane enrichment. © 2025 Institution of Chemical Engineers.