Fabrication and Characteristics of Methyl-Modified TiO₂-SiO₂ Membrane by Sol-Gel Method: Effect of Titania Content

Abstract

Titania-doped methyl-modified silica membrane was prepared via an acid-catalyzed sol-gel method using tetraethylorthosilicate and methyltriethoxysilane as the silicon source and tetraethylorthosilicate as the titanium source. The influence of titanium/silicon molar ratio (n_Ti) on the properties of TiO₂-SiO₂ sol and microstructure of unsupported TiO₂-SiO₂ membrane was systematically studied. The gas permeance and vapor stability of TiO₂-SiO₂ membrane were also tested. The results showed that, as n_Ti increased, the density, viscosity, refractive index and viscous activation Gibbs free energy of TiO₂-SiO₂ sol gradually decreased, while the particle size increased. The existence of Si-CH₃ and Ti-O-Si bonds in TiO₂-SiO₂ membrane proved that the hydrophobic modification was successful and that SiO₂ was chemically bonded to TiO₂, respectively. The titanium element exists in form of Ti-O-Si structure and anatase phase TiO₂ in TiO₂-SiO₂ membrane. When operated at 150 °C and a pressure difference of 0.3 MPa, the H₂ permeance and H₂/CO₂ permselectivity of TiO₂-SiO₂ membrane with n_Ti=0.1 is 6.84 × 10⁻⁶mol·m⁻²·Pa⁻¹·s⁻¹ and 6.96, respectively. After aging in the moist circumstance for 9 d, the H₂ permeance of TiO₂-SiO₂ membrane reduced by 6.86%, while the H₂/CO₂ permselectivity increased by 2.71%.

Keywords:

• Titania-doped
• Sol-gel method
• Vapor stability
• H₂/CO₂ permselectivity

Additional information

Funding

This work was supported by the Scientific Research Project of Shaanxi Education Department, China [No. 19JC017], the Xi'an Municipal Science and Technology Project of China [No. 2020KJRC0025] and the Scientific Research Project of Shaanxi province of China [2021GY-147 and 2021JQ-688].