Porous silica membranes with various Ni contents (Si/Ni = 4/1 to 1/1) were prepared by using sol–gel techniques for the separation of H2 at around 500C. The H2-selective permeation characteristics and hydrothermal stability of the membranes were tested in steam at 500C to show that hydrothermal treatment of the membranes before being exposed to H2 was quite effective in preventing the further densification of Ni-doped amorphous silica networks due to a reduction in H2 and sintering in steam (500C, 70kPa). The Ni-doped silica membranes (Si/Ni = 2/1) fired in steam (partial pressure of 90kPa) at 650C were found to exhibit an asymptotic steady permeance of 1.6 x 10−5m3(STP)/m2skPa for He and 4.6 x 10−6m3(STP)/m2skPa) for H2, with a high selectivity of 1450 (He/N2) and 400 (H2/N2); even after being kept in steam (90kPa, 500C) for some 6 days. The permeance ratio of H2/H2O was found to depend not only upon the permeance ratio of He/H2 but also upon the Ni content, and the maximum permeance ratio observed was 37 for a Ni-doped silica membrane (Si/Ni = 1/1).

Hydrogen Permeation Characteristics and Stability of Ni-doped Silica Membranes in Steam at High Temperature. M.Kanezashi, M.Asaeda: Journal of Membrane Science, 2006, 271[1-2], 86-93