JPS6071003A - Hydrogen gas permeable membrane - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a laminated membrane, by supplying hydrogen gas to the stock material side of a laminated membrane while reducing the pressure in the permeation side thereof, and occluding the hydrogen gas with the metal hydride membrane of the laminated membrane to prevent the metal hydride membrane from containing moisture. CONSTITUTION:As metal hydride, one having hydrogen equilibrium decomposition pressure of about 1-10kg/cm<2> in the vicinity of a room temp. is pref. from a practical aspect and a rare earth element-Ni type alloy can be used. A metal hydride membrane can be usually formed by a vacuum vapor deposition method, a sputtering method or an ion beam method. In a hydrogen permeable membrane, metal oxide 2 is exposed in a stock material side 1 and a base plate comprising a high-molecular polymer membrane 5 is laminated between metal oxide 2 and the metal hydride membrane 4 in a permeation side 3. This membrane is arranged so that the metal oxide membrane is positioned in the stock material side remote from the metal hydride membrane.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a permeable membrane that selectively permeates hydrogen gas,
Specifically, the present invention relates to a hydrogen gas permeable membrane using metal hydride.

Hydrogen gas is generally produced industrially by decomposition of hydrocarbons and ammonia, or water electrolysis, but such hydrogen gas contains impurity gases such as inert gases such as helium and argon, as well as oxygen, water, and nitrogen. , -Contains carbon oxide, carbon dioxide, sulfur dioxide, nitrogen oxide, methane, etc., so for example, in the semiconductor industry, metal processing industry, or instrumental analysis field, after the above Japanese hydrogen gas is purified. I am using it.

As a method for purifying such hydrogen gas, for example, a method is known in which hydrogen gas is supplied to a thin film made of a palladium alloy under pressure and heat, and the hydrogen gas is selectively permeated to purify hydrogen gas. ing. However, according to this method, the alloy itself is very expensive, the required energy cost is also high because it is necessary to process hydrogen gas at high temperature, and furthermore, the palladium alloy film has poor durability. There are some difficulties.

On the other hand, in recent years, it has been proposed that certain metals or alloys selectively absorb hydrogen gas to form metal hydrides, and that hydrogen gas purification has been proposed that takes advantage of the properties of these metal hydrides to reversibly release hydrogen. It has come to be. As a metal hydride thin film that can be used for this purpose, for example, a thin film of metal hydride deposited on a substrate has been proposed (Japanese Unexamined Patent Publication No. 58-27976), but commercially available Ordinary hydrogen gas contains various impurities, especially about 4.0 ppm of water and about s ppm of oxygen, so metal hydrides such as rare earth alloys, magnesium alloys, etc.
When using iron-based alloys, these metal hydrides are oxidized and degraded in the presence of oxygen and water, so metal hydrides! The hydrogen permeability of the membrane, and therefore the degree of purification of the resulting hydrogen gas, also decreases over time.

The present invention was made in order to solve the above-mentioned problems in hydrogen gas permeable membranes, and the metal hydride does not deteriorate, so the hydrogen gas permeation performance and hydrogen gas purification ability are stable over a period of time. The purpose is to provide a hydrogen gas permeable membrane.

The present invention provides a permeable membrane that selectively permeates hydrogen gas from the raw material side to the permeate side. and a metal hydride film capable of selectively absorbing hydrogen, characterized in that the metal oxide film is provided closer to the raw material than the metal hydride film.

In the hydrogen gas permeable membrane of the present invention, the polymer membrane used as the substrate is a support for multiple metal oxide membranes and metal hydride membranes, and the permeable membrane of the present invention consisting of a laminated membrane has strength and In addition to imparting flexibility, it is necessary to have hydrogen permeability, and in particular, the gas permeability coefficient at room temperature is 10 = cJ (STP) cm / cJ seconds.
cm) is preferably 1 g or more.

Therefore, preferred specific examples include natural rubber, poly(4-methylpentene-1), polydimethylsiloxane, and ethyl cellulose. Further, a porous resin film, such as a porous film made of polytetrafluoroethylene or polypropylene, is also a preferred example.

Further, as the metal oxide film having hydrogen gas permeability and moisture resistance, for example, a magnesium oxide film is suitable. As is already known, such a magnesium oxide film can be obtained by heating and evaporating metal magnesium in a reduced pressure oxygen atmosphere and vacuum depositing it on a substrate or a metal hydride film to be described later. The film thickness is 0.01~0.
5 μm is preferred. When the film thickness is thinner than 0.01 μm, it is not preferable because it is difficult to form a uniform continuous film and the moisture proofing property decreases. However, when it is thicker than 0.5 μm, the film becomes inflexible and cracks occur, which is not preferable.

The metal hydride constituting the metal hydride film is not particularly limited, but it has a weight of 1 to 10 kg/c+ at around room temperature.
It is preferable from a practical point of view to have a hydrogen equilibrium decomposition pressure of approximately J, and the hydrogen gas permeable membrane of the present invention can effectively prevent deterioration of metal hydride membranes due to moisture, as will be described later.
A rare earth element alloy, for example, a rare earth element-Ni alloy can be used. The metal hydride film can be formed by a conventionally known method such as a normal vacuum evaporation method, sputtering method, or ion beam method. As is already known, when depositing an alloy, if the constituent metals have different vapor pressures, the deposited film will not have a predetermined alloy composition, so it is necessary to adjust the raw material composition appropriately. Alternatively, a so-called flash vapor deposition method may be used.

The appropriate thickness of the metal hydride film is in the range of 0.01 to 10 μm.

The hydrogen gas permeable membrane of the present invention is obtained by activating the laminated membrane obtained as described above. That is, hydrogen gas is supplied to the raw material side of the laminated membrane, and the pressure on the permeate side is reduced, so that the metal hydride film in the laminated membrane absorbs hydrogen gas.

Of course, it is clear that this activation treatment may be performed at the same time as hydrogen gas permeation.

In the permeable membrane of the present invention, the metal oxide film is laminated closer to the raw material side than the metal hydride film, and acts as a barrier layer against moisture in the metal hydride membrane, so that moisture is not contained in the metal hydride membrane. This prevents deterioration of the metal hydride film.

Furthermore, even if the raw material hydrogen gas swells the polymer film, such as hydrocarbon or hydrogen sulfide, if the metal oxide film is placed closer to the raw material than the polymer film, the metal hydride The membrane acts as a barrier to these impurity gases of the polymer membrane, protecting it and increasing its durability.

The drawing is a sectional view showing an embodiment of the hydrogen gas permeable membrane of the present invention.

Basically, in the hydrogen gas permeable membrane of the present invention, as shown in FIG. It is constructed by laminating substrates made of polymer films 5, but as shown in FIG. Further, as shown in FIG. 3, a substrate 5 may be further laminated on the raw material side 1 in order to protect the surface of the metal oxide film 2 on the raw material side 1. . Also,
As shown in FIG. 4, if necessary, the substrate 5, the metal oxide 11'ii2, and the metal hydride film 4 may be laminated in this order from the raw material side 1.

In manufacturing the hydrogen gas permeable membrane of the present invention, a metal hydride film is deposited on a substrate, and then a metal oxide film is further deposited on the substrate to form a permeable film as shown in FIG. However, a metal hydride film and a metal oxide film are each deposited on separate substrates, and the metal oxide film is stacked on the raw material side with respect to the metal hydride film. Good too. For example, the permeable membrane shown in FIG. 2 can be manufactured by such a method. Further, for example, the transmission film shown in FIG. 5 includes a laminated film 6 in which a metal oxide film 2 is formed on a first substrate 5, and a metal hydride film 4'' is formed on a second substrate 5''. A laminated film 6' is formed by bonding the substrates 5 and 5' together.

The hydrogen gas permeable membrane of the present invention is disposed with respect to hydrogen gas such that the metal oxide film is located on the raw material side rather than the metal hydride film, and usually pressurized hydrogen gas is supplied to the raw material side. Purified hydrogen gas is obtained as permeate gas on the permeate side.

Therefore, even if the hydrogen gas that permeates through the permeable membrane contains moisture, this moisture is prevented from permeating through the permeable membrane by the metal oxide membrane, and the hydrogen gas that does not contain moisture passes through the metal hydride membrane. Since the hydrogen gas obtained on the permeate side does not contain moisture, the metal hydride membrane does not deteriorate due to moisture, and therefore hydrogen gas can be selectively permeated stably over a long period of time for purification. Hydrogen gas can be obtained.

Furthermore, according to the permeable membrane of the present invention, even when the raw material hydrogen gas contains impurity gases such as hydrocarbons and hydrogen sulfide that cause the polymer membrane to swell, the permeable membrane is closer to the raw material side than the polymer membrane. Laminating a metal oxide film protects the substrate and increases its durability, since the metal oxide film acts as a barrier to these impurity gases in the polymer film.

The present invention will be explained below with reference to Examples.

A polytetrafluoroethylene porous membrane having a thickness of 60 μm and micropores with a pore diameter of about 0.1 μm was used as an example substrate, and a magnesium oxide film was deposited thereon.

This oxide film was formed after the pressure inside the vapor deposition reaction vessel was reduced to I x 10-54 Torr, and then the oxygen partial pressure was reduced to 3 x I Q T
Then, metal magnesium was heated by resistance heating, the distance between the evaporation source and the porous membrane was set to 25 cm, and the film formation rate was 100 people/min, and the film thickness was 2,000 people. A vapor-deposited film was formed.

Separately, the raw metal composition was adjusted so that the deposited film was LaNi5 under a reduced pressure atmosphere of I A metal hydride film was deposited on a substrate.

Each of the laminated films obtained above was bonded to a substrate as shown in FIG. 2 to fabricate a hydrogen gas permeable film according to the present invention.

The metal oxide film of this permeable membrane is placed on the raw material side, hydrogen gas is supplied to the raw material side at a pressure of 10 kg/cut at room temperature, and the permeated side is evacuated to carry out an activation treatment in which the metal hydride absorbs hydrogen. The process was repeated 20 times to obtain a hydrogen gas permeable membrane of the present invention.

Next, 99.9% pure industrial hydrogen gas (dew point -60°C) was supplied under pressure to the raw material side of this membrane, and when the hydrogen gas that permeated through the membrane was analyzed, the dew point was -75°C. . Moreover, no impurity gas was detected by analysis using a gas chromatograph (detectors TcD, TiD).

When the above operation is repeated, according to the permeable membrane of the present invention, the dew point of the permeated hydrogen changes after 100 cycles and after 1000 cycles.
The dew point of the permeated hydrogen gas was -75°C after 100 cycles, but for comparison, when a hydrogen permeable membrane with only a metal hydride film formed on the substrate was used, the dew point of the permeated hydrogen gas was -75°C after 100 cycles. However, after 1ooo cycle, the temperature was -65℃
Therefore, the comparative hydrogen gas permeable membrane hardly exhibited hydrogen selective permeation performance.

[Brief explanation of drawings]

1 to 5 are sectional views showing examples of the hydrogen gas permeable membrane of the present invention. 1... Raw material side, 2... Metal oxide film, 3... Permeation side, 4... Metal hydride film, 5... High molecular weight membrane (substrate) Patent applicant Sekisui Chemical Co., Ltd. Co., Ltd. Representative Mototoshi Fujinuma 1 Fig. 2 Fig. 1N 4th g z-" 3 f--) 55th" 6゛[4゜

Claims (1)

[Claims] (1) In a permeable membrane that selectively permeates hydrogen gas from the raw material side to the permeate side, this permeable membrane is composed of a polymer membrane that has hydrogen permeability and a metal oxide membrane that has hydrogen permeability and moisture resistance. , a laminated film comprising a metal hydride film capable of selectively absorbing hydrogen, wherein the metal oxide film is provided closer to the raw material than the metal hydride film. film.