Natural gas upgrading by high-performance ultra-thin CHA membranes

Ultra-thin (450 nm) CHA zeolite membranes were assessed for upgrading a synthetic natural gas mixture with a composition representative of the natural gas after a Joule Thomson process. At a feed pressure of 30 bar(a), the membranes provided high fluxes and excellent selectivity for CO 2 /C x H y , CO 2 /N 2 , and N 2 /C x H y separations. The most favourable conditions for CO 2 removal were observed near 25 °C, yielding a CO 2 flux of 1.2 (mol/m 2 ·s) and a permeance of 13 × 10 −7 (mol/m 2 ·s·Pa) (3900 GPU). At this temperature, selectivities for CO 2 /CH 4 , CO 2 /C 2 H 6 , and CO 2 /C 3 H 8 were 68, 101, and 190, respectively. For N 2 separation, the optimal temperature was ∼35 °C, where a N 2 flux of 2.5 × 10 −3 (mol/m 2 ·s) and a permeance of 1 × 10 −7 (mol/m 2 ·s·Pa) (300 GPU) were achieved, along with selectivities of 5 (N 2 /CH 4 ), 9 (N 2 /C 2 H 6 ), and 15 (N 2 /C 3 H 8 ). A process simulation based on these separation properties indicated that only 11.3 m 2 of membrane area is required to upgrade 1000 Nm 3 /h of natural gas to pipeline quality at 30 bar(a). These results demonstrate the strong promise of ultra-thin CHA membranes for efficient natural gas upgrading.