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 alpha-Al2O3 disk supported mesoporous gamma-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, O-2, N-2, CH4, and SF6 with helium permeance in the range of (1.0-3.5)x10(-7)mol(m(2) center dot s center dot Pa)(at 200 degrees C, 0.3MPa). Considering the membrane calcined at 500 degrees C, it is found that the permselectivity of the He (0.255nm) 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 degrees C, 500 degrees C and 550 degrees C deteriorate under a H2O partial pressure of 200, 500 and 1000kPa, respectively.