China is abundant in low-concentration coalbed methane resources (with a CH₄ concentration of less than 30%), which were once directly vented into the atmosphere due to safety restrictions, resulting in both resource waste and aggravated greenhouse effect. Pressure swing adsorption (PSA) has emerged as the core purification technology for low-concentration coalbed methane owing to its low energy consumption and high efficiency, and high-performance adsorbents are the key to this technology. This paper reviews the research progress of relevant adsorbents in recent years, and systematically summarizes the research advances of four types of key materials, namely carbon-based adsorbents, zeolite molecular sieves, metal–organic frameworks (MOFs) and composite materials, in CH₄/N₂ separation. The intrinsic correlations between the composition, pore structure, surface chemical properties of adsorbents and their CH₄ adsorption capacity as well as CH₄/N₂ separation selectivity are emphatically discussed. MOFs, which combine the advantages of high pore volume of carbon-based materials and high stability of zeolite molecular sieves, together with composite materials that feature adjustable pore structure, controllable active sites and multi-material characteristics, are expected to become the most promising adsorbents for efficient CH₄/N₂ separation. This review provides important research insights for the industrial application of PSA purification technology for low-concentration coalbed methane.
Qiao et al. (Thu,) studied this question.