Synthesis of Titania Composite Membranes by the Pressurized Sol-Gel Technique

Crack‐free titania composite membranes have been synthesized from colloidal titania sols (average particle size of 7–16 nm) by the pressurized sol‐gel coating technique. The Knudsen permeability of N2 through the titania membrane layer heat‐treated at 300°C is about 21 × 10‐7–35 × 10‐7 mol/m2·s·Pa at room temperature. The permselectivity and the separation factor of He to O2 in the temperature range of 25°‐245°C are 2.49–2.74 and 1.66–1.84, respectively. The average pore diameters of these membranes estimated from the molecular weight cutoff data (6000–9000) using poly(ethylene glycol) are 3.0–4.0 nm. By doping zirconia into titania membranes, their thermal stability could be improved up to 800°C.