High flux high-silica SSZ-13 membrane for CO₂separation

Abstract

High-silica (gel Si/Al ¼ 100) SSZ-13 membranes were prepared by hydrothermal secondary growth on the surface of a-alumina hollow fiber supports. The membranes were evaluated for their performance in the separation of CO 2 from equimolar mixtures with CH 4 or N 2 . The maximum CO 2 -CH 4 and CO 2 -N 2 separation selectivities were found to be 42 and 12 respectively, with a high CO 2 permeance of 3.0 Â 10 À7 mol m 2 s À1 Pa À1 at 293 K and total feed pressure of 0.6 MPa. At the low aluminum content, the prepared membranes contain a very low number of defects, as follows from their H 2 /SF 6 ideal selectivity of over 500 in the 293-473 K temperature range. Due to their hydrophobicity, water in the feed mixture has only a small influence on the permeance at temperatures above 353 K. Water improves the CO 2 -N 2 and CO 2 -CH 4 selectivity, which is attributed to preferential blocking of the hydrophilic, non-zeolitic defect pores. The hydrothermal stability of the high-silica SSZ-13 membrane was evaluated by a long (220 h) CO 2 -N 2 separation test with a humidified (9.5 kPa H 2 O) feed mixture at 393 K and 0.6 MPa feed pressure. The permeance and selectivity were stable during this endurance test, underpinning the promise of high-silica SSZ-13 membranes for application in the separation of hot and humid gas mixtures. † Electronic supplementary information (ESI) available: Including schemes of experimental setup and membrane module, SEM images of support surface and seed layer, details of adsorption simulations, TGA analysis of detemplation process, mixture separation in pressure gradient mode, water and gas adsorption isotherms, analysis of defect inuence. See

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