Precise pore size modulation of K-MER zeolites for N2 trapping

The separation of nitrogen (N2) and methane (CH4) is a difficult challenge in the field of natural gas purification, especially the removal of small amounts of N2. Here, we have successfully developed a series of pure-phase MER zeolites with controllable Si/Al ratios, showing different N2 trapping effects through an oxalic acid-assisted synergistic fast dynamic crystallization strategy. Among them, K-MER-2.7 showed the most remarkable result, with an N2 adsorption capacity of up to 0.48 mmol g−1 at 273 K, and an N2/CH4 uptake ratio greater than 10. This was attributed to a narrowing of the pores to form ultra-micropores that limited the uptake of larger sized CH4, leading to excellent N2/CH4 selectivity (85.6). Adsorption kinetic experiments and molecular dynamics simulations corroborated the severe hindering effect towards CH4. Breakthrough experiments with a variety of feed gas compositions at different flow rates confirmed the practical feasibility of applying K-MER-2.7 to separate N2/CH4 gas mixtures.