1990 Fiscal Year Final Research Report Summary
Separation of hydrogen from H_2-CO gas mixtures using rare earth hydrogen storage alloy films
| Project/Area Number |
01470074
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
無機工業化学
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| Research Institution | Osaka University |
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Principal Investigator |
ADACHI Gin-ya Osaka Univ, Engineering Professor, 工学部, 教授 (60029080)
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| Co-Investigator(Kenkyū-buntansha) |
IMANAKA Nobuhito Osaka Univ. Engineering Tutor, 工学部, 助手 (30192503)
SAKAGUCHI Hiroki Osaja Univ. Engineering Tutor, 工学部, 助手 (00202086)
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| Project Period (FY) |
1989 – 1990
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| Keywords | LaNi_5 / CaNi_5 / Hydrogen separation / Amorphous / Thin film / Hydrogen storage alloy / Carbon monoxide |
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| Research Abstract |
The resistance of amorphous LaNi_5 and Ca-Ni alloy films to harmful CO in H_2 gas mixtures has been studied and the H_2-CO gas separation has been performed using these films deposited on a Ni-coated polymer membrane. The hydrogen adsorption capacity of the LaNi_5 films decreased about 30% after exposing to the H_2 gas containing CO. The degree of decrement for the films, however, was much smaller than that reported for a crystalline bulk sample.
As the results of separation experiments, hydrogen in the applied gas with a composition of 50 mo1%H_2 - 50 mo1%CO was concentrated to more than 98 mo1% in the permeated gas. The permeation rate for Ni/LaNi_5 films was greater then that for Ni films up to ca. 373 K, but the opposite tendency was observed at above the temperature. The activation energy of hydrogen permeation estimated for the Ni/LaNi_5 film was ca. 30 kJ/mo1H_2 or 14 kJ/mo1H_2 above or below ca. 343 K respectively.
CaNi_5 can absorb much hydrogen at low pressures in comparison with LaNi_5. In order to increase the hydrogen permeation rate, the development of hydrogen separation film using the Ca-Ni alloy has been performed. A gas of 50 mo1%H_2 in an applied H_2-CO gas mixtures was concentrated to as high as 99 mo1% in the permeated gas. The permeation rate of the Ni/CaNi_<4.2> film was four times as large as that of the Ni/LaNi_<5.0> film.
Thermodynamic data have been evaluated from the hydrogen pressurecomposition isotherms in order to clarify the difference of the local environmental structure around hydrogen atoms in LaNi_<5.0> between the amorphous and crystalline films. The dependence of the relative partial molar enthalpies and entropies of hydrogen on hydrogen concentration in the amorphous film was different from that in the crystalline film. The amorphous film appears to have two types of hydrogen sites. One is influenced by lanthanum, and the other is comprised of more nickel atoms. The hydrogen site in crystalline film is only the former.
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