Preparation and hydrothermal stability of organic-inorganic hybrid silica membrane

A new organic-inorganic hybrid microporous membrane was prepared via Sol-Gel method with bridged silsesquioxane (1, 2-bis(triethoxysilyl)ethane, BTESE) as a precursor. Macroporous α-Al₂O₃ disk supported mesoporous γ-Al₂O₃ layer was used as support. Defect-free hybrid silica membrane was deposited on such support by using a stable nano-sized sol and subsequently calcining in pure nitrogen atmosphere. The hybrid SiO₂ membrane as well as the powder was characterized by TG/DSC, BET and gas permeation. The hybrid silica membranes exhibit molecular sieve properties for small gases like He, CO₂, O₂, N₂, CH₄, and SF₆ with helium permeance in the range of (1.0-3.5) × 10^-7mol/(m² ·s ·Pa)(at 200°C, 0.3 MPa). Considering the membrane calcined at 500°C, it is found that the permselectivity of the He (0.255 nm) with respect to CO₂ (0.33nm) is 47, which is much higher than the corresponding Knudsen value (He/CO₂=3.3). Effect of calcination temperature on hydrothermal stability of those microporous membranes was studied in detail. Results show that the performances of hybrid SiO₂ membranes calcined at 450°C, 500°C and 550°C deteriorate under a H₂O partial pressure of 200, 500 and 1000 kPa, respectively.