JP3462604B2 - Method and apparatus for purifying 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 and apparatus for purifying an inert gas, and more particularly to nitrogen, argon, helium, xenon, etc. containing impurities such as carbon dioxide, carbon monoxide, oxygen, hydrogen and water. And an apparatus for purifying an inert gas for obtaining a highly purified gas by removing these impurities from the inert gas.

In the semiconductor manufacturing process, a large amount of hydrogen, oxygen, and other inert gases such as nitrogen, argon, and helium are used. In recent years, with the progress of highly integrated semiconductors, these gases also have extremely high purity. Is required.

[0003]

2. Description of the Related Art As a method for obtaining purified gas by removing carbon monoxide, carbon dioxide, oxygen, hydrogen and water contained as impurities in an inert gas, platinum and palladium catalysts are used to convert them into carbon dioxide gas and water. After conversion, a method of removing generated carbon dioxide and water with an adsorbent such as synthetic zeolite, and a gas containing at least oxygen as an impurity is brought into contact with a catalyst containing nickel, copper or the like as a main component, , A method of fixing a small amount of carbon monoxide, carbon dioxide, hydrogen, etc., and then removing residual impurities such as water and carbon dioxide with an adsorbent such as synthetic zeolite, or nickel for a gas with a relatively large amount of carbon dioxide. , After treatment with a catalyst such as copper, carbon dioxide is mainly removed with an adsorbent such as zinc oxide, and the remaining impurities are absorbed by synthetic zeolite. How to remove the dosage (JP 2
-120212).

[0004]

However, it is difficult to remove oxygen, carbon monoxide, hydrogen, carbon dioxide and the like to a low concentration range such as ppb order only by using a combination of platinum or palladium catalyst and synthetic zeolite or the like. Is. Further, even if only a combination of nickel, copper, etc. and synthetic zeolite can be efficiently removed oxygen and water, etc., if there are many other impurities, especially carbon dioxide, etc., the amount of catalyst and adsorbent must be increased. However, there is a drawback that not only the processing cost becomes expensive, but also the entire apparatus becomes large. Furthermore, when a gas rich in carbon dioxide is treated with a catalyst such as nickel or copper, and then treated with an adsorbent having a high ability to remove carbon dioxide such as zinc oxide in addition to synthetic zeolite, carbon dioxide and moisture However, there is a problem that oxygen, carbon monoxide, hydrogen and the like cannot be removed to a sufficiently low efficiency region. Therefore, it has been strongly desired to establish a method for efficiently removing any of the impurities contained in the gas to an extremely low concentration to obtain a purified inert gas of ultra-high purity.

[0005]

Means for Solving the Problems The inventors of the present invention have dealt with these problems and have conducted research on a method for efficiently obtaining a high-purity purified gas for a long time. As a result, an inert gas containing impurities is removed. First, contact with an adsorbent whose main component is zinc oxide, which has a high carbon dioxide removal capacity, and then contact a catalyst with a large oxygen removal capacity, such as nickel and copper, and an adsorbent whose main component is synthetic zeolite, in that order. The present invention has been completed by finding that a purified inert gas having an extremely high purity can be obtained by the treatment.

That is, the present invention provides a method for purifying an inert gas containing carbon dioxide as an impurity and at least one selected from oxygen, carbon monoxide, hydrogen and water,
Nickel, an adsorbent containing zinc oxide as the main component of the inert gas
Catalysts containing copper or copper as an active ingredient, synthetic zeolites,
This is a method for purifying an inert gas, which is characterized by sequentially contacting with an adsorbent mainly composed of Rica gel or calcium chloride . The present invention also includes carbon dioxide as an impurity,
And a device for purifying an inert gas containing at least one selected from oxygen, carbon monoxide, hydrogen, and water, wherein the adsorbent contains zinc oxide as a main component in order from the gas inlet side to the gas outlet side. A catalyst containing nickel or copper as an active ingredient,
At least two series of purification tubes filled with an adsorbent mainly composed of synthetic zeolite , silica gel or calcium chloride and equipped with a heater are provided, and hydrogen for catalyst regeneration is provided in a pipe on the gas outlet side of the purification tube. It is also an inert gas purification device characterized by connecting a gas supply pipe.
It The present invention is applicable to high-purity purification of inert gases such as nitrogen, argon, helium, neon, xenon, krypton, and mixed gas thereof.

In the present invention, an adsorbent A having a high carbon dioxide removing ability, a catalyst having a high ability to capture oxygen, carbon monoxide and hydrogen, and an adsorbent B having a high ability to remove water are used in combination. Adsorbent A is mainly composed of zinc oxide
In particular, an adsorbent formed by molding the zinc oxide by the present inventors and an adsorbent formed by mixing zinc oxide with aluminum oxide and an alkali compound (Japanese Patent Application Laid-Open No. HEI 0-58).
1-164418, JP-A-02-43917)
Etc. are suitable.

The catalyst filled downstream of the adsorbent A has a high oxygen scavenging ability and is usually nickel.
It contains copper and other active ingredients. Above all, nickel is excellent not only in its ability to capture oxygen even at room temperature, but also in that it can capture impurities such as carbon monoxide, hydrogen and carbon dioxide even in a low efficiency range to a low efficiency range. The nickel catalyst may be nickel alone, but is usually used in the form of being supported on a catalyst carrier such as diatomaceous earth, alumina or silica-alumina in order to enhance the contact efficiency with gas. The content of nickel in the catalyst is usually 5 in terms of metallic nickel.
˜80 wt%, preferably 20 to 80 wt%, and the specific surface area is usually 10 to 300 m ² / g, preferably 3
It is about 0 to 250 m ² / g. Since these catalysts are commercially available, they can be selected from them and used.

Next, as the adsorbent B, which has a high water removing ability, there are synthetic zeolite, silica gel, calcium chloride, etc. Among them, the water removing capacity is large,
In addition, synthetic zeolite is preferable in that impurities such as carbon dioxide and carbon monoxide remaining in the gas can be removed to a low concentration range. As the synthetic zeolite, for example, molecular sieves 3A and 5A (US, manufactured by Union Carbide Co.) are suitable.

Next, the present invention will be described in detail with reference to the drawings. FIG. 1 is a flow sheet of the refining device of the present invention. In FIG. 1, the flow paths 2a and 2b branched from the raw material gas supply pipe 1 are connected to the inlets 3a and 3b of the refining cylinders A and B through valves, respectively. Each of the purifying cylinders A and B is filled with an adsorbent A4 for removing carbon dioxide, a catalyst 5 for trapping oxygen, carbon monoxide and hydrogen, and an adsorbent B6 for removing water, in order from the inlet 3 side, Moreover, the heater 7 is provided. Flow path 2 connected to gas inlets 3a and 3b of purifying cylinders A and B
The flow paths 8a and 8b branched from a and 2b are connected to a regeneration gas discharge pipe 9 via valves, respectively. On the other hand, the gas outlets 10a and 10b of the purification tubes A and B
Is connected to the extraction pipe 12 for the purified gas via valves through flow channels 11a and 11b, respectively.
The flow paths 13a and 13b branched from 11 and 11b are connected to the regeneration gas supply pipe 14 via valves. Further, the self-gas supply pipe 15 branched from the purified gas extraction pipe 12 is connected to the regeneration gas supply pipe 14 via a valve.

Purification of gas and regeneration of catalyst and adsorbent are carried out by switching purifying cylinders A and B alternately. The raw material inert gas is fed from the supply pipe 1 through the flow path 2a to the gas inlet 3
Enter the purifying cylinder A from a. The gas that has entered the purification column A first comes into contact with the adsorbent A4, and among the impurities, mainly carbon dioxide is removed. Next, in contact with the catalyst 5, impurities such as carbon monoxide and hydrogen are removed in addition to oxygen. Adsorbent B continues
By contacting with No. 6, water and other impurities remaining are completely removed, and the highly purified gas is discharged through the outlet 1
0a through the flow path 11a and is withdrawn from the withdrawal pipe 12.

While the gas is being purified in the purification column A, the adsorbent and the catalyst are regenerated in the purification column B. The purification cylinder B is heated by the heater 7 to, for example, 200 to 4
Supplying hydrogen gas alone from the regeneration gas supply pipe 14 while heating to about 00 ° C., or supplying purified self-gas from the supply pipe 15 and mixing it to the purification cylinder B from the outlet 10b via the flow path 13b. As a result, water and other impurities adsorbed on the adsorbent B6 are desorbed, and the oxygen captured by the catalyst 5 reacts with hydrogen by the action of the catalyst 5 to become water, and carbon monoxide, carbon dioxide, etc. It is converted to methane or the like and desorbed, and subsequently carbon dioxide or the like adsorbed on the adsorbent A4 is desorbed and discharged together with the regeneration gas from the discharge pipe 9 through the inlet 3b of the purification cylinder B and the flow path 8b. As a result, the adsorbents A and B and the catalyst are regenerated. By stopping the supply of hydrogen gas and flowing only the purified self-gas, the inside of the system is replaced with the purified gas to be prepared for the next purification step.

In the present invention, the purification column may have a form in which the adsorbent A, the catalyst and the adsorbent B are simultaneously packed in one column as shown in FIG. 1, or the adsorbent and the catalyst may be separated from each other. The form filled with the cylinder may be connected in series. Further, the purification column is usually of two series, but it may be of three or more series if necessary. These are designed according to the size of the device and the layout of the installation site.

The contact temperature of the inert gas with the adsorbent and the catalyst at the time of purification is generally 80 ° C. or lower, but it is usually operated at room temperature, and heating or cooling is not particularly required. The gas flow rate differs depending on the type and concentration of impurities contained, and cannot be specified unconditionally, but normally it is 15
0 cm / sec or less, preferably 1 to 70 cm / se
c, and more preferably 3 to 30 cm / sec.
The pressure is not particularly limited, but it is practically 10 kg /
It is often performed at cm ² G or less.

[0015]

【Example】

Example 1 A refining apparatus having the same structure as that shown in FIG.
An apparatus equipped with a 8.4 mm and 700 mm long stainless steel refining cylinder was used. Zinc oxide, aluminum oxide and anhydrous potassium carbonate were mixed in order from the inlet side into each of the purifying cylinders A and B in a weight ratio of 100: 10: 5, water was added, and the mixture was kneaded and extruded, and then dried.
20 cm of the adsorbent A obtained by baking at 1 ° C. for 1 hour and 2 of N-112 (manufactured by JGC Chemical Co., Ltd.) as a nickel-based catalyst
0 cm, molecular sieve 5A as adsorbent B
(US, manufactured by Union Carbide Co., Ltd.) was filled to 10 cm to prepare an inert gas purifying device.

Oxygen as an impurity was added to this apparatus at 3.1 pp.
m, carbon monoxide 0.5ppm, carbon dioxide 0.6p
5 kg / cm ² G of nitrogen gas containing pm and 0.5 ppm of hydrogen and having a dew point of −78 ° C. (water conversion 0.75 ppm)
Purification was performed under a pressure of ³ Nm ³ / Hr at a rate of ³ Nm ³ / Hr, and impurities in the purified gas at the outlet were analyzed. Hydrogen was measured using a reducing gas analyzer RGA-3 (manufactured by Trace Analytical Co., USA), and other impurities were measured using an atmospheric pressure mass spectrometer (manufactured by Hitachi Tokyo Electronics Co., Ltd.). Purification was continued in this state, and the impurities that would break through first and the time until breakthrough were measured. The results are shown in Table 1.

Comparative Example 1 20 cm of a nickel-based catalyst, 20 cm of the same zinc oxide-based adsorbent A used in Example 1 and molecular sieve 5 in order from the inlet side of each of the purifying cylinders A and B.
Purification was performed in the same manner as in Example 1 except that A (adsorbent B) was charged to 10 cm, and the time required for analysis of the outlet gas and breakthrough was measured. The results are shown in Table 1.

Comparative Example 2 Purification cylinders A and B each had a nickel-based catalyst of 40 cm and a molecular sieve 5A in order from the inlet side.
Purification was carried out in the same manner as in Example 1 except that the gas was charged for 10 cm and the outlet gas was analyzed and the time until breakthrough was measured. The results are shown in Table 1.

[0019]

Table 1 Purity of Purified Gas and Breakthrough Time Impurities (ppb) CO CO ₂ H ₂ O ₂ H ₂ O Example 1 <0.1 <0.03 <0.5 <0.03 < 0.1 Comparative Example 1 <0.1 0.3 <0.5 0.3 <0.1 Comparative Example 2 <0.1 0.6 <0.5 0.2 <0.1 Breakthrough Time First Impurities that have passed through (hr) Example 1 54 CO Comparative Example 1 43 CO Comparative Example 2 26 CO ₂

[0020]

INDUSTRIAL APPLICABILITY The present invention removes various kinds of impurities such as carbon dioxide, oxygen, hydrogen, carbon monoxide and water contained in an inert gas by combining an adsorbent having a specific performance and a catalyst in a predetermined order. As a result, each impurity is removed to an extremely low concentration, and an extremely high-purity purified gas can be obtained for a long time. Moreover, the removal efficiency
Since it is expensive , the device can be miniaturized and can be installed in an expensive and limited space such as in a semiconductor manufacturing facility.

[0021]

[Brief description of drawings]

FIG. 1 is a flow sheet of an inert gas purification device.

[Explanation of symbols]

1 supply pipe 3 entrance 4 Adsorbent A 5 catalyst 6 Adsorbent B 7 heater 9 discharge pipe 10 exit 12 Withdrawal tube A and B Purification tube

Front page continuation (51) Int.Cl. ⁷ identification code FI C01B 23/00 C01B 23/00 Q B01D 53/36 Z B01J 23/74 321M (58) Fields investigated (Int.Cl. ⁷ , DB name) B01D 53/04 C01B 23/00

Claims (3)

(57) [Claims] 1. A method for purifying an inert gas containing carbon dioxide as an impurity and at least one selected from oxygen, carbon monoxide, hydrogen and water.
With an adsorbent mainly composed of zinc oxide, nickel or copper
Catalyst as active ingredient, synthetic zeolite, silica gel or
A method for purifying an inert gas, which comprises sequentially contacting with an adsorbent containing calcium chloride as a main component . 2. The inert gas is nitrogen, argon, helium,
The method according to claim 1, which is xenon, krypton, neon, or a mixed gas thereof. 3. A refining apparatus for an inert gas containing carbon dioxide as an impurity and at least one selected from oxygen, carbon monoxide, hydrogen and water, which is sequentially provided from the gas inlet side to the gas outlet side. Purification of at least two series in which an adsorbent containing zinc oxide as a main component, a catalyst containing nickel or copper as an active ingredient, a synthetic zeolite , an adsorbent containing silica gel or calcium chloride as a main component is filled and a heater is provided. An apparatus for purifying an inert gas, comprising a cylinder, wherein a hydrogen gas supply pipe for catalyst regeneration is connected to a gas outlet side pipe of the purification cylinder.