Highly permeable N 2 /CH 4 separation SAPO-34 membranes synthesized by diluted gels and increased crystallization temperature

Abstract Synthesis conditions were optimized for synthesizing SAPO-34 membranes towards N 2 /CH 4 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 N 2 permeance was observed in this study. The membranes separated N 2 from CH 4 with N 2 permeance as high as 1300 GPU and selectivity of 7.4 at 23 °C for a 50/50 N 2 /CH 4 mixture. Furthermore, membranes were reproducible and effectively separated gas mixtures having low N 2 content which are relevant compositions of natural gas. More specifically, membranes separated N 2 from CH 4 with N 2 permeance as high as 1160 GPU and selectivity of 7.1 at 23 °C for an 18.5/81.5 N 2 /CH 4 mixture. The resultant SAPO-34 membranes have potential for economic N 2 rejection in natural gas processing.