Highly permeable N₂/CH₄ separation SAPO-34 membranes synthesized by diluted gels and increased crystallization temperature

Synthesis conditions were optimized for synthesizing SAPO-34 membranes towards N₂/CH₄ separation. Compared to previous SAPO-34 membrane preparations, synthesis gels were diluted 1.3-2.7 times and an increased crystallization temperature was used. As a result, a 3-4 fold increase in N₂ permeance was observed in this study. The membranes separated N₂ from CH₄ with N₂ permeance as high as 1300 GPU and selectivity of 7.4 at 23 °C for a 50/50 N₂/CH₄ mixture. Furthermore, membranes were reproducible and effectively separated gas mixtures having low N₂ content which are relevant compositions of natural gas. More specifically, membranes separated N₂ from CH₄ with N₂ permeance as high as 1160 GPU and selectivity of 7.1 at 23 °C for an 18.5/81.5 N₂/CH₄ mixture. The resultant SAPO-34 membranes have potential for economic N₂ rejection in natural gas processing.