Preparation and Properties of Hydrothermally Stable γ‐Alumina‐Based Composite Mesoporous Membranes

We report here on our thermal and hydrothermal investigations comparing mesoporous γ‐Al 2 O 3 membrane with single and double dopant membranes prepared by the sol–gel method. Improvements in the hydrothermal stability of mesoporous γ‐Al 2 O 3 by transition (Ga 3+ ) or rare‐earth (La 3+ ) cations are discussed, along with the effectiveness of double dopant (Ga 3+ –La 3+ ). The amounts of Ga 2 O 3 oxide used varied between 0.0 and 30 mol% and those of La 2 O 3 between 6 and 15 mol%. The thermal and hydrothermal (up to 75% steam) stability of nine types of membranes fabricated on an asymmetric porous α‐Al 2 O 3 support by means of a dip‐coating process was characterized by H 2 gas permeation at 500°C. By conducting tests with wide variations in dopant concentrations, material characterizations, and gas permeance performance, we have been able to optimize the key parameters for hydrothermally stable systems.