Microstructural investigations of tubular α-Al2O3-supported γ-Al2O3 membranes and their hydrothermal improvement

γ-Al2O3 meso-porous membranes supported by tubular α-Al2O3 substrates were prepared by using the sol-gel method and their nanostructural characterizations were performed for the first time with high-resolution transmission electron microscopy (HRTEM) before and after hydrothermal treatment at 500 °C. The HRTEM images and pore size distribution (PSD) analyses revealed that the morphologies as well as the characteristics of the powder and membrane samples prepared from the same boehmite are not identical. γ-Al2O3 and La2O3-Ga2O3 doped-γ-Al2O3 (LGA) membranes supported by α-Al2O3 were also fabricated and characterized under thermal and hydrothermal conditions for the purpose of comparisons. Finally, two type α-Al2O3/γ-Al2O3/SiO2 (AA-SiO2) and α-Al2O3/La2O3-Ga2O3-γ-Al2O3/SiO2 (ALGA-SiO2) membranes have been synthesized and the gas permeance of the membrane were measured in the temperature range 100-500 °C.