Highly Permeable AlPO-18 Membranes for N₂/CH₄ Separation

Herein we demonstrate that AlPO-18 membranes can separate N 2 /CH 4 gas mixtures at unprecedented N 2 permeances. The best membranes separated N 2 /CH 4 mixtures with N 2 permeances as high as 3076 GPU and separation selectivities as high as 4.6. Gas mixture separation data, N 2 and CH 4 adsorption isotherms, ideal adsorbed solution theory (IAST), and breakthrough experiments were collected to understand the separation mechanisms. Competitive adsorption and differences in diffusivities were identified as the prevailing separation mechanisms. Differences in diffusivity played a more dominant role than the competitive adsorption, and led to nitrogen selective membranes.