High flux high-silica SSZ-13 membrane for CO2 separation

High-silica (gel Si/Al = 100) SSZ-13 membranes were prepared by hydrothermal secondary growth on the surface of alpha-alumina hollow fiber supports. The membranes were evaluated for their performance in the separation of CO2 from equimolar mixtures with CH4 or N-2. The maximum CO2-CH4 and CO2-N-2 separation selectivities were found to be 42 and 12 respectively, with a high CO2 permeance of 3.0 x 10(-7) mol m(2) s(-1) Pa-1 at 293 K and total feed pressure of 0.6 MPa. At the tow aluminum content, the prepared membranes contain a very low number of defects, as follows from their H-2/SF6 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 CO2-N-2 and CO2-CH4 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) CO2-N-2 separation test with a humidified (9.5 kPa H2O) 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.