Highly Permeable AIPO-18 Membranes for N2/CH4 Separation

Herein we demonstrate that AIPO-18 membranes can separate N-2/CH4 gas mixtures at unprecedented N-2 permeances. The best membranes separated N-2/CH4 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 CH4 adsorption isotherms, ideal adsorbed solution theory (LAST), 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.