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.