Development of hydrothermally stable sol–gel derived La2O3-doped Ga2O3–Al2O3 composite mesoporous membrane

Mesoporous γ-Al2O3-based membranes, namely γ-Al2O3 alone, La2O3-doped Al2O3, Ga2O3-doped Al2O3 and La2O3-doped Ga2O3–Al2O3, were prepared by the sol–gel method to test their stability in hydrothermal conditions at 500 °C. The hydrothermal (up to 75% steam) stability of all fabricated membranes formed on an α-Al2O3 porous support through dip coating process was characterized by H2 gas permeation. The H2 gas permeance was drastically increased in 2 h under hydrothermal conditions for all samples except La2O3-doped Ga2O3–Al2O3. Steady-state gas permeance performance and unchanged morphology as well as pore size before and after hydrothermal test revealed that the La2O3-doped Ga2O3–Al2O3 membrane in the composition of La:Ga:Al = 6:30:64 mol% with γ-Al2O3 phase structure could be withstand during prolonged exposure to high temperature (500 °C), especially in the presence of steam. The hydrothermal test indicates that the membrane prepared is viable to be of use as an intermediate layer for fabricating a microporous gas separation membrane.