Synthesis and characterization of SiO2-based porous glass membranes for CO2 separation

SiO2-based porous glass membrane was synthesized on porous Si3N4 substrates through the new cake-filtration/melting process. The microstructure and gas separation characteristics of the membrane were investigated. SiO2-B2O3-Na2O glass powder suspension in alcohol (the glass composition: SiO2 72.4mol%, B2O3 20.4mol%, Na2O 7.2mol%) was filtered through a disk-like porous Si3N4 substrate to form the cake layer thereon. It was heated under vacuum at a temperature of 1473 K for 0.6 ks, then quenched to room temperature in air, and soaked in 3N HNO3 at 363K for 0.9ks to 7.2ks to leach out the soluble components. The obtained membrane had micropores of 0.46nm diameter and a gradient in composition from the surface to core. The permeance of N-2 through the membrane from the gas mixture CO2 and N-2 (CO2:N-2=1:9 ratio) was larger than that of CO2. The permeability ratio (P-CO2/P-N2) decreased from 0.17 to 0.04 with the increase of temperature from room temperature to 373K. From these results, it was concluded that the membrane had a high selectivity of N-2 permeation.