Green Hydrogen Separation from Nitrogen by Mixed-Matrix Membranes Consisting of Nanosized Sodalite Crystals

Graphical Into the Matrix : Mixed-matrix membranes with uniformly dispersed nanosized sodalite crystals in a polymeric matrix are prepared. The sodalite nanocrystals are synthesized free of organic template with large external surface area and monomodal particle-size distribution. The sodalite nanocrystals with a suitable aperture size of the cages (2.8 Å) allow only H 2 to penetrate whereas N 2 is rejected. The mixed-matrix membranes show high H 2 flux and selectivity and will be of great importance for synthetic ammonia processing, which demands and releases a large amount of H 2 . Nanosized sodalite (Nano-SOD) crystals were used as active filler to prepare mixed-matrix membranes (MMMs) for promoting the H 2 /N 2 gas-separation performance. The Nano-SOD crystals with extremely small crystallites (40–50 nm) were synthesized from a colloidal suspension free of organic structural directing agent and uniformly dispersed in the polyetherimide (PEI) matrix. The Nano-SOD filler with a suitable aperture size (2.8 Å) allowed only H 2 molecules to pass through and rejected the N 2 , thus improving the selectivity of the membranes. The high dispersion of Nano-SOD crystals in the polymer matrix and the interactions between the inorganic and organic phases greatly improved the membrane separation performance and minimized interfacial holes. The MMMs showed a high H 2 permeability (≈7155.1 Barrer at 25 °C under atmospheric pressure) and an ideal H 2 /N 2 selectivity factor of approximately 16.9 in a single gas test. Moreover, in a gas mixture (H 2 /N 2 , 25–100 °C), the selectivity factor increased significantly to approximately 30.9. The high stability of the MMMs, which consist of highly dispersed Nano-SOD crystals in a PEI matrix for H 2 /N 2 separation (6 weeks continuous test), makes them an important material for ammonia synthesis applications that require and also release a large amount of H 2 .