JPH0834733B2 - Method and device for removing trace amount of hydrogen in inert gas - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently removing a trace amount of hydrogen contained in an inert gas and an apparatus therefor.

[0002]

2. Description of the Related Art In many manufacturing processes, rare gases such as helium, neon, argon, krypton, and xenon, and inert gases such as nitrogen are often required to have high purity. In the production of, very high purity inert gas is required. Another atom
In the field of power, purification and reprocessing of helium for multipurpose HTGR
Laser and plasma research facilities
Separation, concentration and removal of elemental isotopes are required.

Commercially available noble gases for industrial use contain impurities such as hydrocarbons, carbon monoxide, carbon dioxide, oxygen, nitrogen, hydrogen and water, and hydrocarbons are also contained in industrial nitrogen gas. Since impurities such as carbon monoxide, carbon dioxide, oxygen, hydrogen, and water are contained, these impurities must be removed for high purification.

In order to obtain a high-purity inert gas, various purification methods have been adopted depending on the type of impurities contained in the inert gas. For example, a method of removing oxygen and carbon monoxide by an oxidation reaction of nickel or the like is adopted.
Hydrocarbons are converted into carbon dioxide and water by a combustion reaction using palladium as a catalyst, and are removed by contacting with carbon dioxide and water originally mixed with an adsorbent such as molecular sieve.

Among these, the method of converting hydrocarbons in an inert gas into carbon dioxide and water by a combustion reaction using palladium as a catalyst requires coexisting oxygen or newly added oxygen, and the hydrocarbons Since it is usually difficult to react oxygen with oxygen in excess and deficiency, it is necessary to make a complicated system such as further removing excess oxygen.

In addition, in the method of removing oxygen and carbon monoxide by the above-mentioned nickel oxidation reaction and the method of converting hydrocarbons into carbon dioxide and water by a combustion reaction using palladium as a catalyst, an inert gas containing nitrogen is used. It is not possible to obtain a high purity gas.

Therefore, as a method for purifying an inert gas containing nitrogen as an impurity, a method using a single metal mainly composed of titanium or zirconium or a getter of various alloys has been developed. The reaction cylinder filled with this getter can simultaneously remove nitrogen, hydrocarbons, carbon monoxide, carbon dioxide, oxygen, hydrogen and water at high temperature.

However, since the method using a getter is disadvantageous for absorbing hydrogen because the reactor is operated at a high temperature, impurities other than hydrogen can be removed to a level of several ppb or less, but Regarding number 1
It can only be purified to levels of 0 to 100 ppb.

As a measure for improving this point, Japanese Unexamined Patent Publication No.
The inventions described in JP-A-116607 and JP-A-2-293310 are known.

That is, in Japanese Unexamined Patent Publication No. 2-116607, nitrogen, oxygen, water, methane, which are impurities other than hydrogen in the inert gas, are contained in the first-stage getter cylinder.
Carbon monoxide and carbon dioxide are removed, and only the hydrogen is removed by the second-stage getter cylinder. In this case, both the first-stage getter cylinder and the second-stage getter cylinder are set to a temperature of 350 to 400 ° C.

Further, in Japanese Unexamined Patent Publication No. 2-293310, hydrocarbons, nitrogen, oxygen, water, which are impurities other than hydrogen in the rare gas at high temperature, are introduced by a first-stage getter cylinder.
Methane, carbon monoxide, and carbon dioxide are removed, and then hydrogen is converted to water at 40 ° C. or lower by a nickel-based catalyst filled in the upper part of the second-stage filling cylinder, and at the lower part of the second-stage filling cylinder. Moisture is adsorbed by the molecular sieves filled in.

[0012]

With the progress of higher integration of semiconductors, the purity level required in the production of VLSI is being required to be 1 ppb or less for each impurity concentration. However, the removal rate of hydrogen at a high temperature when using a reaction tube filled with a getter is not sufficient, and further improvement is required to remove low-concentration hydrogen. Also in the field of nuclear energy
But more compact and compact hydrogen isotope than ever before
There is a need for a method of removing and concentrating.

In the above-mentioned Japanese Patent Laid-Open No. 2-116607, a zirconium-aluminum alloy getter for the purpose of removing hydrogen is provided at the subsequent stage of the getter-filling cylinder. Adsorption and desorption of hydrogen occur reversibly, and a sufficient removal level is not reached.

In Japanese Patent Application Laid-Open No. 2-293310, as described above, hydrogen is converted to water at 40 ° C. or lower by using a nickel-based catalyst filled in the upper part of the second-stage charging cylinder, and Water is adsorbed by the molecular sieves filled in the lower part of the second filling cylinder, but the hydrogen removal level in this case is not always satisfactory (in the examples, the hydrogen concentration in the source gas was Is 1 ppm, and the hydrogen concentration in the purified gas is 30 ppb or less), and there is also the trouble that molecular sieves must be further placed in order to remove the generated water.

Further, in both JP-A-2-116607 and JP-A-2-293310,
When it loses its capacity by absorbing a certain amount of hydrogen, the packing must be replaced with a new one or regenerated, but the usage status of the packing cannot be confirmed at a glance, so the outlet is a purified gas. There is a problem that it is necessary to determine the time for replacement or regeneration by analyzing the gas . Under such a background, the present invention aims to provide an industrial method capable of irreversibly removing a trace amount of hydrogen contained in an inert gas at a low temperature and easily confirming a use state. It is what Note that
In the following, "hydrogen" means hydrogen such as deuterium and tritium.
It is a concept that includes isotopes.

[0016]

The method for removing a trace amount of hydrogen according to the present invention is characterized in that an inert gas containing a trace amount of hydrogen is brought into contact with a silver ion exchanged zeolite having oxygen coordinated in advance at 100 ° C. or lower. It is a thing.

The trace hydrogen removing apparatus of the present invention comprises a reaction tube (1) filled with silver ion-exchanged zeolite, a gas inlet (2) for introducing gas into the reaction tube (1), and the reaction tube.
It is provided with a gas outlet (3) for discharging gas from (1). In this case, a heating mechanism (4) for heating the silver ion-exchanged zeolite packed in the reaction tube (1) for oxygen coordination or regeneration can be further provided.

The present invention will be described in detail below.

Examples of the inert gas applicable to the method of the present invention include rare gases such as helium, neon, argon, krypton and xenon, and nitrogen. The inert gas containing trace hydrogen, except carbon monoxide from industrial gas, carbon dioxide, oxygen, nitrogen, hydrogen, the impurity components such as water, Note gas containing hydrogen and the like, Ya fine weight aqueous fraction It does not matter if it contains oxygen . These impurities may be removed before the contact with the oxygen-coordinated silver ion-exchanged zeolite according to the method of the present invention.

The silver ion-exchanged zeolite is composed of Me _x (AlO ₂ ) _y (S
Alkali metal ions of zeolites with the molecular formula iO ₂ ) _z
At least a part of the (Me) part, particularly 10 to 98% or more, is ion-exchanged with silver ions. As the zeolite, various zeolites such as X-type, Y-type, A-type and ZSM-5 type are used. The silver ions of this silver ion-exchanged zeolite take in oxygen at a slow rate at room temperature and at a fast rate near 300 ° C. Further, the silver ion gives oxygen taken up in advance to hydrogen that has been taken in at a low temperature, and accelerates a reaction of converting it into water.

Therefore, the silver ion-exchanged zeolite is brought into contact with an inert gas containing oxygen at a temperature of about 300 ° C. in advance so as to be in an oxidized state in which oxygen is coordinated.
After returning the temperature to 0 ° C. or lower, it is brought into contact with an inert gas containing hydrogen. The temperature of 100 ° C. or lower is for preventing re-desorption of water, and it can be brought to usually 80 ° C. or lower, further 60 ° C. or lower, especially about room temperature, or even lower temperature.

Upon contact with the oxygen-coordinated silver ion-exchanged zeolite, hydrogen in the inert gas is oxidized and converted into water. Since the generated water is immediately adsorbed on the zeolite skeleton, the water concentration in the purified gas does not rise. Also,
Since the reaction between hydrogen and oxygen is an irreversible reaction due to chemical oxidation adsorption, there is no possibility that hydrogen will be desorbed again due to the influence of temperature, flow rate, pressure change and the like.

As hydrogen in the inert gas is removed, oxygen in the oxygen-coordinated silver ion-exchanged zeolite is gradually lost and the color changes from white to black. Since the hydrogen removing ability is lost after removing a certain amount of hydrogen, it is necessary to regenerate the oxygen-coordinated silver ion-exchanged zeolite at an appropriate stage before deactivation. This regeneration can be easily achieved by subjecting the oxygen-coordinated silver ion-exchanged zeolite having a reduced hydrogen removing ability to a heat treatment in an inert gas stream containing oxygen. The heating temperature is preferably about 250 to 400 ° C, but is not necessarily limited to this range. Instead of regenerating the oxygen-coordinated silver ion-exchanged zeolite, it can be disposable and exchanged with another new oxygen-coordinated silver ion-exchanged zeolite. Whether to recycle or to throw it away is determined by the scale and other circumstances.

As an apparatus for carrying out the above method, a reaction tube (1) filled with silver ion exchanged zeolite,
An apparatus provided with a gas inlet (2) for introducing gas into the reaction tube (1) and a gas outlet (3) for discharging gas from the reaction tube (1) is used. In this case, a heating mechanism (4) for heating the silver ion-exchanged zeolite packed in the reaction tube (1) for oxygen coordination or regeneration can be further provided.
Further, two such reaction tubes (1) may be provided in parallel, and while one is removing hydrogen in the inert gas, the other is regenerated or exchanged.

The reaction tube (1) is provided with an observation window (5) for identifying the color change of the oxygen-coordinated silver ion-exchanged zeolite or detects the color change of the oxygen-coordinated silver ion-exchanged zeolite. It is desirable to attach a replacement timing sensor (6) for this purpose.

In order to remove various impurities contained in the inert gas, a getter of titanium, zirconium, zirconium-iron, titanium-zirconium, zirconium-vanadium-iron, etc. is provided upstream of the reaction tube (1). It is also possible to install a getter cylinder filled with.

[0027]

In the present invention, since the oxygen-coordinated silver ion-exchanged zeolite is used, hydrogen in the inert gas reacts with oxygen even at room temperature due to the action of oxygen coordinated with the silver ion introduced by ion exchange, Converted to water.

Moreover, the trace amount of hydrogen contained in the inert gas only reacts stoichiometrically with oxygen, and when hydrogen as a reaction target component does not exist, oxygen is released from the oxygen-coordinated silver ion-exchanged zeolite. Not released.

Since the skeleton is zeolite, water produced by the reaction of hydrogen and oxygen is immediately adsorbed on the zeolite.

As described above, the oxygen-coordinated silver ion-exchanged zeolite has both the function of converting hydrogen into water and the function of adsorbing the produced water, and these functions are 100%. It is demonstrated at low temperatures below ℃ (for example, at room temperature).

In addition, the oxygen-coordinated silver ion-exchanged zeolite recovers the hydrogen-removing ability again by removing a certain amount of hydrogen and then heating it in the presence of oxygen.

[0032]

EXAMPLES The present invention will be further described with reference to examples.

Example 1 FIG. 1 is an explanatory view showing an example of a removing apparatus of the present invention.

(1) is a reaction tube having an outer diameter of 38.1 mm and an inner diameter of 3
It has the dimensions of 2.6 mm and height 127 mm. (2) is a gas inlet for introducing an inert gas, (3) is a gas outlet for discharging gas from the reaction tube (1), (5) is a transparent observation window, (7) is a flow controller, and (8) ) Is a gas filter for removing particles.

A spherical silver ion-exchanged zeolite having a diameter of 1.5 mm, in which 50% of sodium ions were ion-exchanged with silver ions (X-type zeolite was used as the zeolite), was heated at 300 ° C. using argon gas having an oxygen concentration of 20%. After oxygen was coordinated by oxidation, it was allowed to cool to room temperature.
As a result, the silver ion-exchanged zeolite was oxidized to become an oxygen-coordinated silver ion-exchanged zeolite. 75 cc of this oxygen-coordinated silver ion-exchanged zeolite was filled in the reaction tube (1).

Then, the flow controller (7) and the gas inlet
Argon gas containing 1.3 ppm of hydrogen was introduced into the reaction tube (1) through (2) at 2 liter / min and 1 atm and led out through the gas outlet (3). The hydrogen concentration in the purified gas derived from the gas outlet (3) was measured using a gas chromatograph mass spectrometer (QP-300) manufactured by Shimadzu Corporation. The results are shown in Table 1. At the same time, when the outlet water concentration was measured with a crystal oscillation type moisture meter (MAH-2) manufactured by Shimadzu Corporation, the dew point of the purified gas was -98 ° C.
It was below.

Table 1 Impurity name Inlet concentration Outlet concentration Detection limit Hydrogen 1.3 ppm Below detection limit 5 ppb

The oxygen-coordinated silver ion-exchanged zeolite in the reaction tube (1) changes its color from white to black due to the reaction with hydrogen in argon gas.
By monitoring more, the usage status can be confirmed, and the replacement timing can be surely known.

Based on the results of Table 1, the integrated removal amount of hydrogen in argon gas was measured for the following three types of fillers. (a) 50% silver ion-exchanged zeolite that has not been previously heat-oxidized (b) Oxygen-coordinated silver ion-exchanged zeolite obtained by heat-oxidizing (a) above (c) Sufficient for (b) above Oxygen-coordinated silver ion-exchanged zeolite obtained by deactivating hydrogen by passing through it and then subjecting it to thermal oxidation regeneration treatment at a temperature of 300 ° C.

That is, room temperature argon gas containing 150 ppm of hydrogen was continuously introduced at a flow rate of 1 liter / min into the reaction tube (1) filled with each of the above-mentioned fillers, and was discharged from the gas outlet (3). The hydrogen concentration in the generated outlet gas was measured. The results are shown in Figure 2.

From FIG. 2, it is found that when the filler of (b) is used,
Although the breakthrough state is reached in about half an hour, the filler of (c) which is regenerated is also in the breakthrough state in about eight and a half hours, indicating that regeneration can be almost completed. Note that (a), (b), (c)
In each case, the dew point of the outlet gas was −98 ° C. or lower.

Embodiment 2 FIG. 3 is an explanatory view showing another example of the removing apparatus of the present invention.

In Example 1, the purpose was only to remove hydrogen in the inert gas, but in order to remove impurities other than hydrogen in the inert gas at the same time, as shown in FIG.
A getter cylinder (9) filled with a titanium or zirconium getter is provided on the upstream side of (1), and nitrogen in an inert gas,
Oxygen, carbon dioxide, carbon monoxide, methane, and water can be removed at the same time.

The getter filled in the getter cylinder (9) of FIG. 3 is a zirconium getter manufactured by SAES, which is heated at an initial temperature of 450 ° C. for 2 hours and then kept at 400 ° C. It was made possible to remove methane, carbon monoxide, carbon dioxide, oxygen, and water in it. Hydrogen can be removed up to the level of 50 to 100 ppb, but in order to further raise the purity of the inert gas, complete hydrogen removal should be performed with the oxygen-coordinated 98% silver ion-exchanged zeolite packed in the reaction tube (1). did. In addition, (10) is a heater and (11) is a heater case.

98% silver ion-exchanged zeolite coordinated with oxygen by previously heating and oxidizing it at 300 ° C. with an argon gas having an oxygen concentration of 20% was allowed to cool to room temperature and then charged into a reaction tube (1). did.

Argon gas containing impurities shown in Table 2 was supplied from the flow rate controller (7) at 2 liter / min and 1 atm,
After passing through the getter cylinder (9), it was introduced into the reaction cylinder (1) and led out through the gas outlet (3). Table 2 shows the results. The dew point of the gas was −72 ° C. at the inlet and −98 ° C. or less at the outlet.

Table 2 Impurity name Inlet concentration Outlet concentration Detection limit Hydrogen 1.3 ppm Detection limit or less 5 ppb Carbon dioxide 0.5 ppm Detection limit or less 2 ppb Nitrogen 1.5 ppm Detection limit or less 4 ppb

Further, in the above-mentioned Example 1, the reaction tube (1)
Although the replacement time is visually determined through the observation window (5) provided in the reaction tube, in this second embodiment, the replacement time determination sensor (6) for recognizing the color is attached to the reaction tube (1). Then, the replacement time is automatically judged and displayed on the sensor amplifier (6a).

Embodiment 3 FIG. 4 is an explanatory view showing still another example of the removing apparatus of the present invention.

In the above-mentioned Examples 1 and 2, the case where the reaction tube (1) was exchanged when hydrogen in the inert gas was absorbed up to a certain amount was shown. As the silver ion exchanged zeolite, a gas containing oxygen was used. Since it has a property that it can be reused for hydrogen removal by returning to the initial state of being oxygen-coordinated by heating with heating, a regenerative removal device using this property is shown in FIG.

In FIG. 4, the inert gas from which oxygen and carbon monoxide have been removed by nickel in the getter cylinder (9) is
Hydrogen, carbon dioxide, and water are removed by a 25% oxygen-coordinated silver ion-exchanged zeolite in the reaction tube (1).

Oxygen coordinated When the 25% silver ion-exchanged zeolite removes a certain amount of impurities, the coordinated oxygen is lost, so the valves (12) and (16) are closed a little before that.
25% silver ion exchange type by supplying inert gas containing oxygen from valve (15), heating reaction tube (1) by heating mechanism (4), and discarding gas at the time of regeneration from valve (14) Oxygen can be coordinated again to the zeolite. After sufficient regeneration, the valves (13), (14), (15) are closed again, and the valves (12), (16) are opened, so that the purification operation can be continued. These series of operations are automatically performed by using a sequencer, and unmanned operation can be performed.

[0052]

EFFECTS OF THE INVENTION According to the present invention, a trace amount of hydrogen contained in an inert gas can be irreversibly removed at a low temperature (for example, room temperature) to below the detection limit, and the produced water is immediately transferred to the zeolite skeleton. It is adsorbed and does not enter the purified gas.

At that time, the trace amount of hydrogen contained in the inert gas only reacts stoichiometrically with oxygen, and when there is no hydrogen to be reacted, the oxygen-coordinated silver ion-exchanged zeolite is used. Since oxygen is not released, there is no risk of oxygen being mixed into the purified gas.

In addition, since the color of the oxygen-coordinated silver ion-exchanged zeolite changes from white to black as the hydrogen is removed, the usage state can be easily confirmed, and the timing of exchange or switching will not be erroneous.

Therefore, the present invention is an epoch-making industrial method for removing a trace amount of hydrogen contained in an inert gas and is extremely useful.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of a removing device of the present invention.

FIG. 2 shows the relationship between the gas introduction time and the hydrogen concentration in the outlet gas when argon gas at room temperature containing 150 ppm of hydrogen was continuously introduced into the reaction tube (1) at a flow rate of 1 liter / min. It is a graph, (a) is a 50% silver ion-exchanged zeolite, (b) is an oxygen-coordinated silver ion-exchanged zeolite, and (c) is an oxygen-coordinated silver ion-exchanged zeolite obtained by a regeneration treatment. The following shows the case of filling.

FIG. 3 is an explanatory view showing another example of the removing device of the present invention.

FIG. 4 is an explanatory view showing still another example of the removing apparatus of the present invention.

[Explanation of symbols]

(1)… Reaction tube, (2)… Gas inlet, (3)… Gas outlet, (4)
... Heating mechanism, (5) ... Observation window, (6) ... Replacement timing determination sensor, (6a) ... Sensor amplifier, (7) ... Flow control device,
(8)… Gas filter, (9)… Getter tube, (10)… Heater, (11)… Heater case, (12), (13), (14), (1
5), (16) ... Valve

Claims (6)

[Claims] 1. A method for removing a trace amount of hydrogen, which comprises contacting an inert gas containing a trace amount of hydrogen with a silver ion-exchanged zeolite having oxygen coordination in advance at 100 ° C. or lower. 2. The removing method according to claim 1, wherein the oxygen-coordinated silver ion-exchanged zeolite having absorbed a certain amount of hydrogen is activated by heat treatment in an inert gas stream containing oxygen. 3. A reaction tube filled with silver ion-exchanged zeolite.
Trace hydrogen in an inert gas comprising (1) and a gas inlet (2) for introducing gas into the reaction tube (1) and a gas outlet (3) for discharging gas from the reaction tube (1) Removal device. 4. A reaction tube filled with silver ion-exchanged zeolite.
(1), a gas inlet (2) for introducing gas into the reaction cylinder (1) and a gas outlet (3) for discharging gas from the reaction cylinder (1),
A device for removing a trace amount of hydrogen in an inert gas, comprising a heating mechanism (4) for heating the silver ion-exchanged zeolite packed in the reaction tube (1) for oxygen coordination or regeneration. 5. The removing apparatus according to claim 3, wherein the reaction tube (1) is provided with an observation window (5) for identifying a color change of the oxygen-coordinated silver ion-exchanged zeolite. 6. The removing apparatus according to claim 3, wherein the reaction tube (1) is further provided with a sensor (6) for determining a replacement time for detecting a color change of the oxygen-coordinated silver ion-exchanged zeolite. .