Insights into the pore size distribution of amorphous silica membranes using gas permeation activation energies

• Published in: Journal of membrane science 2025-01, Vol.713, p.123269, Article 123269
• Main Authors: Kou, Xiaonan, Anjum, Tanzila, Sun, Kuo, Liu, Liang, Ji, Guozhao, Laeeq Khan, Asim, Elma, Muthia, Olguin, Gianni
• Format: Article
• Language: English
• Subjects: Activated transport; Amorphous silica membrane; Effective medium theory; Gas permeation apparent activation energy; Pore size distribution
• ISSN: 0376-7388
• DOI: 10.1016/j.memsci.2024.123269

Silica-based membranes exhibit significant promise for the separation of hydrogen from other larger gas molecules based on size sieving mechanism, particularly when employed in membrane reactors. Nevertheless, the migration of silanol bonds (Si–OH) formed under hydrothermal conditions leads to alterations in pore size, ultimately compromising the performance of the membrane. Therefore, this study focuses on determining the pore size of cobalt-doped silica membranes before and after hydrothermal treatment by the apparent activation energy of gas permeation. The Oscillator model and the effective medium theory are employed to estimate the potential pore size distribution, as well as to calculate the apparent activation energy and permeability. The calculated apparent activation energy is compared with experimental data to identify the most probable pore size distribution, which showed the minimum activation energy error to the experimental value. The calculated permeability based on the identified pore size distribution is in line with experimental permeability, which validated the identified pore size distribution. Since silica-based membrane is generally applied in hydrothermal conditions, our model successfully identifies the changes in pore size of silica-based membranes after hydrothermal treatment. The results demonstrated that hydrothermal treatment significantly impacts the pore size of silica-based membranes. Specifically, 5-membered rings are prevalent in the intact membrane, but after hydrothermal treatment, there is a gradual shift of the pore size distribution towards larger pores, potentially leading to a decrease in sieving performance. This methodology presents a promising approach for determining intriguing pore size information of porous materials. [Display omitted] •The relationship between permeation activation energy and PSD was interpreted.•The pore size change before and after hydrothermal treatment was confirmed.•The superior hydrothermal stability of Co3+Si over Co2+Si arises from the more rigid PSD.