Carbon molecular sieve membranes for natural gas purification: Role of surface flow

Abstract

Carbon molecular sieve membranes (CMSM) were prepared from the pyrolysis of polyimide films within a temperature range of 600 C-800 C under nitrogen stream.The membrane samples were characterized and tested for the permeation of He, CH 4 , CO 2 , and N 2 at different pressures and temperatures, respectively. The CMSM700 membrane (pyrolyzed at 700 C) showed an ideal selectivity of~11 for N 2 /CH 4 with a permeability of 2.18 × 10 −15 mol Á m/m 2 Á s Á Pa for N 2 . The separation mechanism for the N 2 /CH 4 pair was shown to be largely molecular sieving rather than surface flow.The membrane showed an ideal selectivity of~500 for the CO 2 /CH 4 pair with a CO 2 permeability of 9.72 × 10 −14 mol Á m/m 2 Á s Á Pa. The permeability of He was lower than that of CO 2 , suggesting that the surface flow played a significant role in the CO 2 permeation. The updated permeability-selectivity tradeoff curves show that this CMSM membrane compared favourably with other membrane materials reported in the literature for the removal of N 2 and CO 2 from CH 4 for natural gas upgrading. K E Y W O R D Scarbon molecular sieve, CO 2 removal, membranes, N 2 removal, natural gas

Measuring the permeabilities of binary gas mixtures with a novel time‐lag technique

“…The membrane was referred to as CMSM700 for convenience of discussion; details of membrane fabrication have been described elsewhere. [28,29] The membrane sample had a thickness of ~40 μm and a diameter of 2 cm. All the permeation experiments were conducted at room temperature (25 C).…”

Helium separation using membrane technology: Recent advances and perspectives

“…This result denotes that the gas atmosphere also needs to be taken into consideration for CMS membrane preparation [93]. In another study, the CMS with Kapton as precursor presented the feed-pressure sensitive phenomena: for all the gases tested, increasing feed pressure from 15 to 250 kPa resulted in a significant reduction in permeance (25 -50%) [94]. Interestingly, the loss in helium permeability is larger than that in N2 but lower than in CH4.…”

Thin Film Composite Carbon Molecular Sieve Membranes for Efficient Helium and Hydrogen Separation

“…The test temperature also plays an important role on the gas separation performances, for H 2 /He gas pairs, increasing the test temperature from 25°C to 45°C leading to an increment of H 2 permeance from 1359 GPU to 1429 GPU, while at the same time, He permeance increased from 1248 GPU to 1309 GPU, H 2/ He selectivity (1.09) remains nearly unchanged. PPO on ceramic support 716.11 172.80 [10] Metal oxide/PIM-PI 316.23 11.29 [11] Sulfonated phenolic resin 895.79 19.03 [12] Kapton 283.52 354.97 [13] phenolic resin CMS-15cp 117 156 [14] phenolic resin CMS-25cp 48 73 [14] TFC…”