2010 Volume 36 Issue 5 Pages 472-479
A sol–gel method was applied for the preparation of palladium-doped silica membranes for hydrogen separation. Hydrogen permeation performance and stability (thermal, hydrothermal) were evaluated by measuring the time and temperature dependence of gas permeances (N2, H2, He) in N2 and steam atmospheres (steam: 70 kPa) at 500°C, respectively. It was found that the Pd-doped silica layer has a thickness of approximately 80 nm, and Pd particles of several nanometers were well dispersed in an amorphous silica matrix. Pd-doped silica membranes (Si/Pd=3/1) fired at 550°C in air were quite stable in N2 atmosphere at 500°C, but a drastic decrease of gas permeances (He, H2, N2) and an increase of activation energy of gas permeation (He, H2) were observed under H2 atmosphere at 500°C due to aggregation of Pd particles. Pd-doped silica membranes (Si/Pd=3/1) fired at 550°C in H2 showed high stability in hydrogen and steam atmospheres (steam: 70 kPa) at 500°C. This is because well-dispersed Pd particles in amorphous silica networks could not move in hydrogen and steam atmospheres.
