Hydrogen Permeability of Melt-Spun Ni-Nb-Ta-Zr-Co Amorphous Alloy Membrane and Its Application to Hydrogen Production by Methanol Steam Reforming
Shin-ichi YAMAURA, Hisamichi KIMURA, Akihisa INOUE, Yoichiro SHIMPO, Motonori NISHIDA and Shigeyuki UEMIYA
Abstract:The Ni40Nb20Ta5Zr30Co5 amorphous alloy membranes were prepared by a single-roller melt-spinning technique. The crystallization temperature of the alloy is 825K in an Ar atmosphere. Hydrogen permeability of the alloy was measured at the temperature of 573-673K. As a result, it was found that the initial permeability measured at 673K was higher than 1(10-8mol·m-1·s-1·Pa-1/2 and that the permeability significantly degraded during the measurement. However, the lower the measurement temperature was, the smaller the degradation of permeability became. The permeability of the alloy measured at 573K was kept constant at 5~10-9mol·m-1·s-1·Pa-1/2 during the measurement. Then the hydrogen production by methanol steam reforming was conducted by using the amorphous alloy membrane. As a result, pure hydrogen was extracted by the amorphous alloy membrane from a reformed gas consisting of H2, N2, CO2 and CO and its separation property did not degrade during the experiment for 6 h. Moreover, it was found that the amount of hydrogen flux depended on the flow rate of Ar sweep gas introduced into the lower-side chamber of the reactor. From this observation, the hydrogen permeability of the membrane during the methanol steam reforming was roughly estimated. The estimated permeability during the reforming is about 3.4~10-9mol·m-1·s-1·Pa-1/2. The value is smaller than that obtained from the permeation measurement with pure H2, which may come from pressure loss caused by the boundary film layer on the membrane surface and from surface contamination such as CO adsorption. The potential of amorphous alloy membranes for hydrogen production has been successfully demonstrated. Key Words:Melt-spinning, Amorphous alloy, Hydrogen permeation, Hydrogen separation, Methanol steam reforming