Microporous sol–gel derived aminosilicate membrane for enhanced carbon dioxide separation

A new aminosilicate, sol‐gel derived microporous inorganic membrane has been developed for enhanced CO 2 separation in applications such as removal of metabolic CO2 from the breathing loop of the NASA extravehicular mobility unit (EMU), natural gas purification, or CO2 capture from coal-fired power plant emissions. This membrane consists of an inorganic, amorphous silica matrix of pore size 4‐5 ˚ A, containing randomly dispersed amine ( NH2) functional groups in order to enhance its CO2 selectivity, due to preferential adsorption of CO2 in the membrane pore walls and simultaneous blocking of permeation of other gases (O2 ,N 2 and CH4). It is found that the gas feed condition during permeation (partial pressure of CO2, relative humidity), post-synthetic treatments and aging, affect significantly the separation performance of the membranes. At this stage of development, with feeds of 1‐20 vol.% CO 2 and 0‐40% relative humidity at 22 ◦ C, the highest CO2:N2 separation factor was in the range 100‐200, while the CO 2 permeance was in the range 0.1‐1.5 cm 3 (STP)/(cm 2 min atm). The results suggest that controlling the membrane pore size and method of activation of amine groups are the most critical factors for improving the CO2-permselectivity of the membrane. © 2004 Elsevier B.V. All rights reserved.