Preparation and CO2 separation properties of amine-modified mesoporous silica membranes

Mesoporous silica membranes were prepared on porous alumina supports by both hydrothermal and sol–gel spin-coating methods. SEM images showed that these techniques deposited dense mesoporous silica layers of 200 and 500 nm, respectively, on the alumina supports. TEM and XRD observations showed that these membranes have a highly ordered cubic structure with a pore diameter of 2 nm. Gas permeation properties of these mesoporous silica membranes were governed by the Kundsen diffusion mechanism. Surface modification of the pore walls of mesoporous silica membranes by grafting amino-silane greatly improved the CO2 permselectivities. The amine-modified mesoporous silica membranes showed high CO2/N2 separation properties for a mixture of 20% CO2 and 80% N2 at 373 K. The CO2/N2 selectivities of the membranes prepared using hydrothermal and sol–gel spin-coating methods were 50 and 800, respectively.