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

Abstract

A new aminosilicate, sol–gel derived microporous inorganic membrane has been developed for enhanced CO 2 separation in applications such as removal of metabolic CO 2 from the breathing loop of the NASA extravehicular mobility unit (EMU), natural gas purification, or CO 2 capture from coal-fired power plant emissions. This membrane consists of an inorganic, amorphous silica matrix of pore size 4–5 Å, containing randomly dispersed amine ( NH 2) functional groups in order to enhance its CO 2 selectivity, due to preferential adsorption of CO 2 in the membrane pore walls and simultaneous blocking of permeation of other gases (O 2, N 2 and CH 4). It is found that the gas feed condition during permeation (partial pressure of CO 2, 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 CO 2:N 2 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 CO 2-permselectivity of the membrane.