Chemical Research in Chinese Universities ›› 2026, Vol. 42 ›› Issue (1): 158-166.doi: 10.1007/s40242-026-5270-6

• Research Articles • Previous Articles     Next Articles

Tailoring Cation Charge-to-Size Ratios in Zeolite Y for High-performance Methane/Nitrogen Separation

TAO Zeyu1,2, TIAN Yuanmeng1,2, SHANG Shanshan1,2, BELMABKHOUT Youssef3, SHANG Jin1,2,4   

  1. 1. City University of Hong Kong Shenzhen Research Institute, Shenzhen 518057, P. R. China;
    2. School of Energy and Environment, City University of Hong Kong, Kowloon, Hong Kong 999077, P. R. China;
    3. Applied Chemistry and Engineering Research Centre of Excellence (ACER CoE), Mohammed VI Polytechnic University (UM6P), Lot 660, Hay Moulay Rachid, Ben Guerir 43150, Morocco;
    4. Low-carbon and Climate Impact Research Center, School of Energy and Environment, City University of Hong Kong, Kowloon, Hong Kong 999077, P. R. China
  • Received:2025-11-07 Online:2026-02-01 Published:2026-01-28
  • Contact: SHANG Jin,E-mail:jinshang@cityu.edu.hk;BELMABKHOUT Youssef,E-mail:youssef.belmabkhout@um6p.ma E-mail:jinshang@cityu.edu.hk;youssef.belmabkhout@um6p.ma
  • Supported by:
    This work was supported by the Project of the Science and Technology Innovation Commission of Shenzhen Municipality, China (No. JCYJ20240813153123031) and the Research Grants Council of Hong Kong, China (Nos. CityU 11317722, 11310223, 11313125).

Abstract: Low-concentration methane (CH4) resources, such as coalbed methane (CBM) and coal mine methane (CMM), represent a vast but underutilized source of clean energy, primarily due to the difficulty in separating CH4 from nitrogen (N2). Adsorptive separation offers a promising pathway, yet conventional adsorbents suffer from limited selectivity. Here, we report a substantial improvement in the CH4/N2 selectivity of large-pore FAU zeolites by modulating their cations with smaller charge-tosize ratios. Combined analyses of adsorption isotherms, isosteric heats, and density functional theory (DFT) binding energies reveal that this strategy suppresses N2 adsorption by weakening gascation electrostatic interactions, while concurrently enhancing CH4 uptake through confinement effects that enable a CH4 molecule to interact with multiple cations. By leveraging this strategy, Cs/TMA-Y, incorporating the cations featuring the smallest charge-to-size ratio in this study (cesium: Cs+ and tetramethylammonium: TMA+), exhibited the highest CH4/N2 separation factor under both static and dynamic conditions, along with excellent reusability. Notably, Cs/TMA-Y also delivered the highest CH4/N2 selectivity (7.5) reported to date under dynamic binary conditions (50/50, vomlue ratio). Process simulations further identified vacuum swing adsorption (VSA) as the most effective operational mode, highlighting the practical potential of this material. This study establishes a mechanistic framework for cation-controlled CH4/N2 separation and provides new design principles for zeolitic adsorbents targeting efficient methane upgrading. Furthermore, this strategy opens a promising pathway to enhance confinement effects in medium- and large-pore zeolites, extending their applicability to a broad range of adsorption- and catalysis-related applications.

Key words: Methane upgrading, Greenhouse gas valorization, Adsorptive CH4/N2 separation, Zeolite, Cation charge-to-size ratio