Fabrication and Evaluation of Trimethylmethoxysilane (TMMOS)-Derived Membranes for Gas Separation

• Main Authors: Yoshihiro Mise, So-Jin Ahn, Atsushi Takagaki, Ryuji Kikuchi, Shigeo Ted Oyama
• Format: Article
• Language: English
• Published: MDPI AG 2019-09-01
• Series: Membranes
• Subjects: silica-based membrane; hydrogen separation; CVD; pore size control; trimethylmethoxisilane; separation mechanism
• Online Access: https://www.mdpi.com/2077-0375/9/10/123

Gas separation membranes were fabricated with varying trimethylmethoxysilane (TMMOS)/tetraethoxy orthosilicate (TEOS) ratios by a chemical vapor deposition (CVD) method at 650 °C and atmospheric pressure. The membrane had a high H₂ permeance of 8.3 × 10^−7 mol m^−2 s^−1 Pa^−1 with H₂/CH₄ selectivity of 140 and H₂/C₂H₆ selectivity of 180 at 300 °C. Fourier transform infrared (FTIR) measurements indicated existence of methyl groups at high preparation temperature (650 °C), which led to a higher hydrothermal stability of the TMMOS-derived membranes than of a pure TEOS-derived membrane. Temperature-dependence measurements of the permeance of various gas species were used to establish a permeation mechanism. It was found that smaller species (He, H₂, and Ne) followed a solid-state diffusion model while larger species (N₂, CO₂, and CH₄) followed a gas translational diffusion model.