Hydrogen-permeable metal membranes for high-temperature gas separations

Improvement of high temperature stability of Pd coating on Nb by intermediate layer comprising NbC and Nb2C

“…The initial pressure of H 2 gas in hydrogen absorption experiment was adjusted to be 13.3 Pa. This value of H 2 pressure is significantly smaller than the upstream H 2 pressures commonly employed in the permeation experiments in this field [3][4][5][6][7][8][9][10][11][12]. In general, however, the rates of hydrogen absorption and permeation become more sensitive to surface states as pressure decreases [15].…”

“…Edlund et al [6,7] developed porous oxide intermediate layers to prevent the interdiffusion between Pd and V. The Pd layers employed in their study, however, were rather thick (25 m), and hence the amount of Pd necessary to prepare the composite membrane was comparable with conventional Pd membranes. The present authors have prepared non-porous Nb 2 …”

“…Group 5 metals (V, Nb and Ta) have higher hydrogen permeabilites, lower prices and richer natural resources than Pd which has been widely used as a membrane material. Surfaces of group 5 metals, however, are sensitive to poisoning by impurities such as oxygen, and hence it is common to prepare thin Pd films on the surfaces of permeation membranes as protection layers [2][3][4][5][6][7][8][9][10][11][12]. The hydrogen permeability of such composite membranes, however, declines at elevated temperatures (>673 K) due to the degradation in coating effect caused by interdiffusion between Pd and base metals [6,7].…”

Hydrogen permeable membranes based on niobium foils coated with layer of tungsten and molybdenum in niobium solid solution characteristics research

“…It is believed that the most promising coating for niobium membrane is palladium or its alloys up to several microns thick [6][7][8][9][10][11][12][13][14], performing both protective and catalytic functions. However, problems facing the use of niobium composite membranes are: low thermal stability of the palladium coating, insufficient obstacle to transition to brittle condition of niobium membranes at operating temperatures.…”

Predictions of H isotope separation using crystalline and amorphous metal membranes: A computational approach

“…Metal membranes have received much attention for the high temperature purification of hydrogen due to their high selectivity over other gases over a wide range of temperatures and pressures (Edlund et al, 1994;Howard et al, 2004;Ma et al, 2003;Morreale et al, 2003;Phair and Donelson, 2006;Sholl and Ma, 2006;Uemiya et al, 2001). The most widely studied metal membranes are composed of Pd-based alloys.…”